DASR 21 - Aircraft Design, Production and Certification

GM 21.1 - General (AUS)

As the sponsor of DASR 21, unless otherwise stated the Authority will mean 'DASA'.

DASR 21 is only applicable to aircraft on the Defence register; non-Defence (civil) registered aircraft will continue to abide by the regulations of the applicable civil aviation authority. 

GM 21.A.3A(a) - System for collection, investigation and analysis of data (AUS)

In the context of this requirement the word 'Collection' means the setting up of systems and procedures which will enable relevant malfunctions, failures and defects to be properly reported when they occur.

There are instances where a failure, malfunction or defect, or analysis of failures, malfunctions or defects represents some level of shortfall to the type design but may not result in a reportable occurrence in accordance with DASR 21.A.3A(b) based on an assessment of the available information at that time. In these situations, the holder ought to make a judgement as to whether the shortfall constitutes a risk or not.

Where the shortfall is judged to be within the level of safety inherent to the certification baseline, the holder should continue monitoring and assessing relevant information for risks to the type design.

Where a risk is judged to exist, the risk or hazard must be eliminated So Far As is Reasonably Practicable (SFARP), or if it is not practicable to do so, minimised SFARP in accordance with the requirements of the Work Health and Safety Act 2011, the Work Health and Safety Regulations 2011 and DASR SMS.A.25(b)(2.2).

In meeting the DASR SMS requirements the holder of the type-certificate, restricted type-certificate, supplemental type-certificate, AUSMTSO authorisation, major repair design approval or any other relevant approval deemed to have been issued under this DASR, should formalise arrangements with operators of the product to ensure timely and effective characterisation and communication of risks when deficiencies are being managed. This may constitute immediate communication in support of the development of a Service Bulletin, MPTF Flight Conditions, a Command Clearance, or other operator decisions affecting ongoing flying; or it may be periodic communication of shortfalls at the discretion of, or agreement with, the operator / down-stream duty holder.

GM1 21.A.3A(b) - Occurrence reporting (AUS)

Relevant design organisations are to independently report on the occurrences to the Authority, with a focus on impact to the on-going validity of the certified design.

Typically, relevant design organisations will be made aware of occurrences by DASR 145 and Continuing Airworthiness Management Organisations (CAMO) fulfilling their reporting requirements.

However, in the course of conduct of design activities, analysis or relevant Military Type-certificate holder obligations, identified occurrences are to be reported to the Authority. These instances may not have a corresponding DASR 145 or CAMO Occurrence Report.

A list of occurrences to be reported are detailed in AMC GR.40 - Occurrence Reporting. This is not a comprehensive list and an additional requirement may need to be considered dependent on the scope of the organisations operations.

The following Sections are the most relevant to DASR 21:

SECTION I: AIRCRAFT FLIGHT OPERATIONS

SECTION II: AIRCRAFT TECHNICAL

SECTION V: IMMEDIATE NOTIFICATION OF ACCIDENTS AND SERIOUS INCIDENTS

In particular:

The products and part and appliances design rules prescribe that occurrences defined as a failure, malfunction, defect or other occurrence which has resulted in or may result in an unsafe condition must be reported to the Authority;

According to the product and part and appliances production rules occurrences defined as a deviation which could lead to an unsafe condition must be reported to the Authority.

GM 21.A.3A(b) Occurrence reporting

For occurrence reporting, additional guidance material can be found in EASA AMC 20-8, (part of EASA AMC 20 document) together with the military specific considerations that can be found in EMAD 20-8 (part of EMAD 20).
In particular:

The products and part and appliances design rules prescribe that occurrences defined as a failure, malfunction, defect or other occurrence which has resulted in or may result in an unsafe condition must be reported to the Authority;

 According to the product and part and appliances production rules occurrences defined as a deviation which could lead to an unsafe condition must be reported to the Authority.

GM 21.A.3B(a) - Airworthiness Directives (AUS)

The Authority will issue all Airworthiness Directives. In some circumstances the Authority’s issuing function may be conducted by a Delegate of the Safety Authority (DoSA) within the scope of their delegation.

GM 21.A.3B(b) - Determination of an unsafe condition

It is important to note that these guidelines are not exhaustive. However, this material is intended to provide guidelines and examples that will cover most cases, taking into account the applicable certification requirements.

1.      INTRODUCTION

Certification or approval of a product, part or appliance is a demonstration of compliance with requirements which are intended to ensure an acceptable level of safety. This demonstration however includes certain accepted assumptions and predicted behaviours, such as:

fatigue behaviour is based on analysis supported by test,

modelling techniques are used for Aircraft Flight Manual (AFM) performances calculations,

the systems safety analyses give predictions of what the systems failure modes, effects and probabilities may be,

the system components reliability figures are predicted values derived from general experience, tests or analysis,

the crew is expected to have the skill to apply the procedures correctly, and

the aircraft is assumed to be maintained in accordance with the prescribed instructions for continuing airworthiness (or maintenance programme), etc.

In service experience, additional testing, further analysis, etc., may show that certain initially accepted assumptions are not correct. Thus, certain conditions initially demonstrated as safe, are revealed by experience as unsafe. In this case, it is necessary to mandate corrective actions in order to restore a level of safety consistent with the applicable certification requirements.

See DASR AMC 21.A.3B(b) for definition of 'unsafe condition' used in DASR 21.A.3B(b).2.

2.      GUIDELINES FOR ESTABLISHING IF A CONDITION IS UNSAFE

The following paragraphs give general guidelines for analysing the reported events and determining if an unsafe condition exists, and are provided for each type of product, part or appliance subject to a specific airworthiness approval: Military Type-Certificates (MTC) or Military Supplemental Type-Certificates (MSTC) for aircraft, engines or propellers, or Australian Military Technical Standard Orders ( AUSMTSO ).

This analysis may be qualitative or quantitative, i.e. formal and quantitative safety analyses may not be available for older or small aircraft. In such cases, the level of analysis are to be consistent with that required by the airworthiness requirements and may be based on engineering judgement supported by service experience data.

2.1    Analysis method for aircraft

2.1.1 – Accidents or incidents without any aircraft, engines, system, propeller or part or appliance malfunction or failure

When an accident/incident does not involve any component malfunction or failure but when a crew human factor has been a contributing factor, this has to be assessed from a human-machine interface standpoint to determine whether the design is adequate or not. Paragraph 2.5 gives further details on this aspect.

2.1.2 – Events involving an aircraft, engines, system, propeller or part or appliance failure, malfunction or defect

The general approach for analysis of in service events caused by malfunctions, failures or defects will be to analyse the actual failure effects, taking into account previously unforeseen failure modes or improper or unforeseen operating conditions revealed by service experience.

These events may have occurred in service, or have been identified during maintenance, or been identified as a result of subsequent tests, analyses, or quality control.

These may result from a design deficiency or a production deficiency (non-conformity with the type design), or from improper maintenance. In this case, it has to be determined if improper maintenance is limited to one aircraft, in which case an airworthiness directive may not be issued, or if it is likely to be a general problem due to improper design and/or maintenance procedures, as detailed in paragraph 2.5.

2.1.2.1 – Flight

An unsafe condition exists if:

There is a significant shortfall of the actual performance compared to the approved performance (taking into account the accuracy of the performance calculation method), or

The handling qualities, although having been found to comply with the applicable airworthiness requirements at the time of initial approval, are subsequently shown by service experience not to comply.

2.1.2.2 – Structural or mechanical systems

An unsafe condition exists if the deficiency may lead to a structural or mechanical failure which:

Could exist in a Principal Structural Element that has not been qualified as damage tolerant. Principal Structural Elements are those which contribute significantly to carrying flight, ground, and pressurisation loads, and whose failure could result in a catastrophic failure of the aircraft.

Typical examples of such elements are listed, as guidance, in EASA Certification Specification for Large Aircraft (CS–25) AMC 25.571(a) 'damage tolerance and fatigue evaluation of structure', and in the equivalent material for rotorcraft.

Could exist in a Principal Structural Element that has been qualified as damage tolerant, but for which the established inspections, or other procedures, have been shown to be, or may be, inadequate to prevent catastrophic failure.

Could reduce the structural stiffness to such an extent that the required flutter, divergence or control reversal margins are no longer achieved.

Could result in the loss of a structural piece that could damage vital parts of the aircraft, cause serious or fatal injuries to persons other than occupants.

Could, under ultimate load conditions, result in the liberation of items of mass that may injure occupants of the aircraft.

Could jeopardise proper operation of systems and may lead to hazardous or catastrophic consequences, if this effect has not been taken adequately into account in the initial certification safety assessment.

2.1.2.3 – Systems

The consequences of reported systems components malfunctions, failures or defects are to be analysed.

For this analysis, the certification data may be used as supporting material, in particular systems safety analyses.

The general approach for analysis of in service events caused by systems malfunctions, failures or defects will be to analyse the actual failure effects.

As a result of this analysis, an unsafe condition will be assumed if it cannot be shown that the safety objectives for hazardous and catastrophic failure conditions are still achieved, taking into account the actual failure modes and rates of the components affected by the reported deficiency.

The failure probability of a system component may be affected by:

A design deficiency (the design does not meet the specified reliability or performance);

A production deficiency (non-conformity with the certified type design) that affects either all components, or a certain batch of components;

Improper installation (for instance, insufficient clearance of pipes to surrounding structure);

Susceptibility to adverse environment (corrosion, moisture, temperature, vibrations etc.);

Ageing effects (failure rate increase when the component ages);

Improper maintenance.

When the failure of a component is not immediately detectable (hidden or latent failures), it is often difficult to have a reasonably accurate estimation of the component failure rate since the only data available are usually results of maintenance or flight crew checks. This failure probability is therefore be conservatively assessed.

As it is difficult to justify that safety objectives for the following systems are still met, a deficiency affecting these types of systems may often lead to a mandatory corrective action:

Back up emergency systems, or

Fire detection and protection systems (including shut off means).

Deficiencies affecting systems used during an emergency evacuation (emergency exits, evacuation assist means, emergency lighting system ...) and to locate the site of a crash (Emergency Locator Transmitter) will also often lead to mandatory corrective action.

2.1.2.4 – Others

In addition to the above, the following conditions are considered unsafe:

There is a deficiency in certain components which are involved in fire protection or which are intended to minimise/retard the effects of fire / smoke in a survivable crash, preventing them to perform their intended function (for instance, deficiency in cargo liners or cabin material leading to non-compliance with the applicable flammability requirements).

There is a deficiency in the lightning or High Intensity Radiated Fields protection of a system which may lead to hazardous or catastrophic failure conditions.

There is a deficiency which could lead to a total loss of power or thrust due to common mode failure.

If there is a deficiency in systems used to assist in the enquiry following an accident or serious incident, eg Cockpit Voice Recorder, Flight Data Recorder, preventing them to perform their intended function, the Authority may take mandatory action.

2.2     Engines

The consequences and probabilities of engine failures have to be assessed at the aircraft level in accordance with paragraph 2.1, and applicable airworthiness requirements. Further guidance at the engine level for those failures considered as hazardous can be found in CS–E–510 under EASA Certification Specification – Engines (CS–E).

The latter will be assumed to constitute unsafe conditions, unless it can be shown that the consequences at the aircraft level do not constitute an unsafe condition for a particular aircraft installation.

2.3     Propellers

The consequences and probabilities of propeller failures have to be assessed at the aircraft level in accordance with paragraph 2.1, and applicable airworthiness requirements. Further guidance at the propeller level for those failures considered as hazardous can be found in CS–P–70 under EASA Certification Specification – Propellers (CS–P).

The latter will be assumed to constitute unsafe conditions, unless it can be shown that the consequences at the aircraft level do not constitute an unsafe condition for a particular aircraft installation.

2.4     Parts and appliances

The consequences and probabilities of equipment failures have to be assessed at the aircraft level in accordance with paragraph 2.1.

2.5     Human factors aspects in establishing and correcting unsafe conditions

This paragraph provides guidance on the way to treat an unsafe condition resulting from a maintenance or crew error observed in service.

It is recognised that human factors techniques are under development. However, the following is a preliminary guidance on the subject.

Systematic review is to be used to assess whether the crew or maintenance error raises issues that require regulatory action (whether in design or other areas), or is to be noted as an isolated event without intervention. This may need the establishment of a multidisciplinary team (designers, crews, human factors experts, maintenance experts, operators etc.)

The assessment is to include at least the following:

Characteristics of the design intended to prevent or discourage incorrect assembly or operation;

Characteristics of the design that allow or facilitate incorrect operation;

Unique characteristics of a design feature differing from established design practices;

The presence of indications or feedback that alerts the operator to an erroneous condition;

The existence of similar previous events, and whether or not they resulted (on those occasions) in unsafe conditions;

Complexity of the system, associated procedures and training (has the crew a good understanding of the system and its logic after a standard crew qualification programme?);

Clarity / accuracy / availability / currency and practical applicability of manuals and procedures;

Any issues arising from interactions between personnel, such as shift changeover, dual inspections, team operations, supervision (or lack of it), or fatigue.

Apart from a design change, the corrective actions, if found necessary, may consist of modifications of the manuals, inspections, training programmes, and/or information to the operators about particular design features. The Authority may decide to make mandatory such corrective action if necessary.

GM 21.A.3B(d)(4) - Compliance time charts for military aircraft

If it is not possible to find mitigations and/or limitations that re-establish compliance with all the applicable safety requirements, an increased risk for an individual failure could be acceptable for a fixed period of time if it is demonstrated that during this period the cumulative probability of catastrophic event per flight hour is still compliant with the type-certification basis.

Exceptions are possible in accordance with National regulations.

The residual risk during the time allowed to fix the defect is to be identified and minimized. Risk assessment techniques could be used to establish the deadline period to fix defects as agreed by the National Authority.

The civil regulations EASA Part 21 (21.A.3B) allow a time period that is directly related to the level risk i.e. higher the risk the shorter the time period. These regulations have hard limits for the maximum instantaneous risk, the maximum risk for an individual aircraft and maximum cumulative risk for the fleet. The basis of these regulations considers typical civil operation, of 10 major safety campaigns during an aircraft life, a hull life of 60,000 hours and that 75% of the risk is attributed to the design. Using the above assumptions they calculate an acceptable time period for restoration of risk levels to certification levels.

For military aircraft the above assumptions are not necessarily valid and the acceptable levels of risk likely to be different, however the principles of the civil system can be equally applied to the military regulations. The graphical representation below, on a logarithmic scale, is adapted from civil regulations AMC to EASA Part 21.A.3B, without the numerical limits, and can be used to enable the Authority (where national regulations allow) to determine appropriate numerical limits, considering the role of the aircraft. There will be different limits for Catastrophic and Hazardous failures.

 

 

GM 21.A.14(b) - Eligibility for alternative procedures

Design organisations approved under DASR 21 Section A Subpart J ("Subpart J MDOA") is to be the normal approach for military type-certification, military supplemental type-certification, approval of major changes to type design or approval of major repair design, except when agreed otherwise by the Authority in accordance with DASR 21.A.14, DASR 21.A.112B and DASR 21.A.432B.

The acceptance of alternative procedures, as defined in DASR AMC 21.A.14(b), is to be limited where the Authority finds it more appropriate for the conduct of military type-certification, military supplemental type-certification, approval of changes to type design, approval of repair design.

Products with simple or limited scope of design 

As the complexity of a product grows, so does the size of a design organisation, along with an increasing degree of specialisation of various parts of the organisation to meet the growing demands of different disciplines. This creates complex communication relationships and workflows.

‘Simple or limited scope of design’ should therefore be understood as the opposite of ‘complex’, see also DASR AMC 21.A.15(b)(6) Level of involvement (LoI).

When determining the complexity of the scope of design, the complexity of the product as well as the structure of the design organisation and relationships with suppliers should be considered.

GM 21.A.14(c) - MTC holder organisations (AUS)

Unlike civil TC obligations, Defence MTC and MRTC obligations are not enforceable via national legislation; DASR (in general) are enforceable for commercial organisations only via contract law. As a result, during the certification or approval process, the Authority will assess a nominated Australian government organisation, and when satisfied issue the Australian MTC to that organisation. That organisation becomes responsible for conduct of the holder obligations as detailed in DASR 21.A.44. DASR AMC 21.A.14(c) defines the assessment criteria for the MTC holder organisation that will conduct the holder responsibilities and manage major changes to the issued MTC or MRTC.

Contracting of holder responsibilities. Where the government organisation does not meet DASR 21.A.14(a) or (b) provisions, or is unable to meet all obligations internally DASR 21.A.14(c) allows for the government organisation to contract the provision of the DASR 21.A.44, DASR 21.A.118A and DASR 21.A.451(a) aligned holder obligations to commercial engineering organisations under DASR 21.A.2.

Where extant procurement/ support arrangements preclude a DASR MDO being contracted under these provisions, the holder organisation will need to use the DASA recognition framework to assist demonstration of the external design organisation as suitable to meet the DASR 21 Subpart J requirements and should also pay particular attention to the equivalence of obligations in the areas of major/minor design change classification (DASR 21.A.91) and reporting to the Authority of failures, malfunctions and defects (DASR 21.A.3A). This is to ensure that Authority interfaces are established at the same equivalent level and hence the Authority’s safety assurance function is not compromised by the incorrect translation of processes. Attention should also focus on the processes to meet the Safety Management System requirements (DASR 21.A.239(d)) equivalence. This is to ensure that the holder organisation’s risk management of operational hazards is based on a sound risk and safety management system.

Application. During the Certification Program culminating in issue of a new MTC or MRTC the Project Office will identify an appropriate government organisation best placed to fulfil the DASR 21.A.44 holder obligations. The PO, in conjunction with the proposed MTC holder will develop an exposition, known as the Type Continued Airworthiness Exposition (TCAE), to show how compliance with the DASR 21J requirements and holder obligations is achieved.

Type Continued Airworthiness Exposition. The purpose of the TCAE is to inform the Authority of the proposed MTC holder management arrangements. The nature of those arrangements will vary considerably between aircraft types, and will depend on the product’s design itself; how the product is operated; and the depth and ability of organisations supporting the product’s design.

A TCAE satisfies the following needs:

Contains, or references to, the agreement that shows how the government organisation, in cooperation with the supporting design organisation(s) will comply with the requirements of DASR 21 Subpart J, including demonstration of compliance in meeting the holder obligation.

Provides confidence that the applicant government organisation understands the nature of the product’s design and its supporting organisations sufficiently to meet the holder obligations.

Identifies the senior Defence engineer responsible for oversighting delivery of the holder functions.

Provides key information influencing the specific solution to meet the MTC holder obligations, particularly where obligations are fulfilled via non-commercial arrangement, eg via foreign military sales or other global fleet support arrangement.

Is a working document able to expand to reflect arrangements for subsequent MTC Changes, MSTC issues, and major repair design approvals.

GM1 to 21.A.15(b) ‐ Certification Programme (AUS)

The certification programme for issue of an MTC / MRTC provided to the Authority by the applicant may take a variety of forms depending on the acquisition arrangements:

if the applicant is an MDOA holder, then the MDOA holder will develop and submit the certification programme;

if the applicant is a Defence Project Office and the prime design / integration organisation is an MDOA holder, or recognised equivalent, then the certification programme will be developed by the prime designer / integrator and provided to the Authority through the Defence Project Office;

if the Defence Project Office is the integrator of multiple design elements, then the Defence Project Office develops and submits the certification programme as the Applicant; or

if design organisation/s do not hold an MDOA or recognised equivalent, or have not been contracted to develop a certification programme, then the Defence Project Office will be required to develop and submit the certification programme as the Applicant.

For software certification aspects, the Authority encourages applicants to develop a Plan for Software Aspects of Certification (PSAC), or equivalent document, and provide it as an enclosure to the certification programme.

GM 21.A.15(b) ‐ Operating Characteristics and Intended Use of the Product (AUS)

The requirements of 21.A.15(b)2 and (b)3 will normally be covered in the aircraft Statement of Operating Intent and Usage (SOIU). Where the requirements of 21.A.15(b)2 and b(3) have been addressed, to the level of detail specified in AMC 21.A.15(b), through an SOIU which has received endorsement from the Authority, the certification programme can include reference to the SOIU without need for duplication of that information. Any detail not sufficiently covered in an endorsed SOIU will need to be provided in the certification programme.

GM 21.A.15(b)(6) ‐ Level of Involvement (AUS)

The Authority will determine the depth and extent of its inspections for each group of compliance demonstration activities and data, based on the information provided in the certification programme and the applicant proposal.

The Authority determination of LoI will be confirmed as part of the Authority’s acceptance of the certification programme. The Authority LoI must be confirmed as completed prior to the applicant issuing the final declaration of compliance required by DASR 21.A.20(d).

The depth and extent of the Authority inspections may change throughout the project in order to account for changes that affect the basis of initial determinations. The provisions of DASR 21.A.257(b) continue to apply.

The Authority may appoint individuals outside the Authority, including individuals within another CAA/MAA, to complete the Authority inspections.

GM 21.A.15(c) ‐ Updates to the certification programme

DASR 21.A.15(b) recognises that the initial submission of the certification programme may not be fully complete, e.g. due to schedule constraints of the design, analysis and testing activities.

Furthermore, even if the initial submission of the certification programme is complete, it may be necessary to amend it throughout the duration of the project.

The certification programme should be updated and resubmitted to the Authority. In particular, updates to the following elements should be provided:

-  any complementary information that was not included in the initial submission of the certification programme;

-  any change in the intended use or kind of operations of the product itself, or of the aircraft on which the product is installed;

-  a change in the key characteristics of the product such as but not limited to any declared limits that are intended to be recorded in the type certificate data sheet (TCDS);

-  any change in the product design or its characteristics that may affect the criteria used to assess the likelihood of an unidentified non‐compliance with the type‐certification basis, operational suitability data (OSD) certification basis or the environmental protection requirements, including the potential impact of that non‐compliance on product safety or environmental protection, as defined in DASR 21.A.15(b)(6);

-  any change to the initial type‐certification basis, OSD certification basis or environmental protection requirements, as applicable to the product, regardless whether the change is initiated by the Authority or by the applicant;

-  any change in the breakdown of the certification programme into compliance demonstration items (CDIs) or in the content of those CDIs;

-  any change in the proposed means of compliance, including its/their methodology;

-  any change in the structure of compliance documents that may affect the determination of the Authority‘s level of involvement (LoI), based on the criteria in DASR AMC 21.A.15(b)(6);

-  any relevant change to the military design organisation approval (MDOA) holder’s personnel (and military design organisation (MDO) suppliers) who are involved in the project; and

-  any changes to the schedule that impact on the LoI of the Authority.

Following each update to the certification programme as submitted by the applicant, the Authority may update the determination of its LoI in accordance with AMC to DASR 21.A.15(b)(6).

GM 21.A.15(e) - Period of validity for the application for a Military Type Certificate (MTC) or Military Restricted Type Certificate (MRTC)

DASR 21.A.15(e) establishes a maximum period of validity for an application for an MTC or an MRTC. During this period, the type‐certification basis, operational suitability data (OSD) certification basis, and the environmental protection requirements (hereinafter referred to as the ‘certification basis’), established in accordance with DASR 21.A.17A, DASR 21.A.17B and DASR 21.A.18, remain effective. However, the period of validity of the certification basis is limited so that the standards established as part of the certification basis at the time of application do not become outdated.

For various reasons (e.g. development, business, commercial, etc.), the applicant may not be able to complete the certification within the established time limit. In this case, the applicant can apply for an extension of the initial application (see DASR 21.A.15(f)):

In this case, the applicant proposes a ‘new target date’ to the Authority for the issuance of the certificate. Respecting the time limits established under 21.A.15(e), the Authority may then use that date to notify airworthiness codes and standards that will become the reference for a revised certification basis.

GM 21.A.15(f) - Period of validity for the application for a Military Type Certificate (MTC) or Military Restricted Type Certificate (MRTC)

DASR 21.A.15(e) establishes a maximum period of validity for an application for an MTC or an MRTC. During this period, the type‐certification basis, operational suitability data (OSD) certification basis, and the environmental protection requirements (hereinafter referred to as the ‘certification basis’), established in accordance with DASR 21.A.17A, DASR 21.A.17B and DASR 21.A.18, remain effective. However, the period of validity of the certification basis is limited so that the standards established as part of the certification basis at the time of application do not become outdated.

For various reasons (e.g. development, business, commercial, etc.), the applicant may not be able to complete the certification within the established time limit. In this case, the applicant can apply for an extension of the initial application (see DASR 21.A.15(f):

In this case, the applicant proposes a ‘new target date’ to the Authority for the issuance of the certificate. Respecting the time limits established under 21.A.15(e), the Authority may then use that date to notify airworthiness codes and standards that will become the reference for a revised certification basis.

GM 21.A.16A - Airworthiness Codes (AUS)

Rather than define a Defence-unique Airworthiness Code, the Authority has elected to recognise the suite(s) of airworthiness design requirements, ie Airworthiness Codes, prescribed by several other CAAs and MAAs that have been demonstrated to achieve safe flight, and then prescribe supplementation as required. The Defence Aviation Safety Design Requirements Manual (DASDRM) identifies the Authority recognised Airworthiness Codes.

GM1 21.A.16B - Special conditions (AUS)

The Airworthiness Code selected for use under DASR 21.A.16A may contain deficiencies against contemporary airworthiness requirements and/or may not account for Defence’s unique Configuration, Role and Environment (CRE). This may require the application of special conditions in addition to an Airworthiness Code. The Defence Aviation Safety Design Requirements Manual (DASDRM) defines 'essential' design requirements and standards that must be applied as special conditions to supplement Airworthiness Codes due to deficiencies in the Codes or to account for the Defence CRE in addition to the reasons described in DASR 21.A.16B(a). The DASDRM also defines a number of ‘recommended’ design requirements and standards for which compliance is not prescribed, but which should be applied where reasonably practicable.

GM 21.A.16B - Special Conditions

General

The term ‘novel or unusual design features’ should be judged in view of the applicable certification basis for the product. A design feature, in particular, should be judged to be a ‘novel or unusual design feature’ when the certification basis does not sufficiently cover this design.

The term ‘unsafe condition’ is used with the same meaning as described in DASR GM1 21.A.3B(b).

The term ‘newly identified hazards’ is intended to address new risks that may be recognised in the design (e.g. questionable features) or its operational characteristics (e.g. volcanic ash) for which there is not yet enough in‐service experience.

GM1 21.A.17A - Type Certification Basis (AUS)

The Type Certification Basis (TCB) for a new Defence aircraft should be developed and agreed with the Authority as early as practicable in the aircraft acquisition lifecycle. While an Authority‐agreed TCB should be pursued prior to entering into an acquisition contract, this will not always be possible. In those cases, the Acquisition Project Office may elect to present a draft TCB for Authority assessment as a cost and schedule risk reduction measure.

The TCB for a Defence aircraft must be consistent with Defence’s intended role and operating environment for the aircraft. Information on the intended role and operating environment is to be provided in the certification programme, per the requirements at DASR 21.A.15(b)4 and (b)5, but will normally reference out to an endorsed Statement of Operating Intent and Usage (SOIU) which provides this detail. TCB agreement is obtained through approval of the certification programme in accordance with DASR 21.A.15(b).

In the aircraft Type Certification domain, Configuration, Role and Environment (CRE) is a pivotal concept. Where an ab initio Type Certification programme is proposed for a Defence aircraft, defining the CRE is essential to ensure that the basis of certification is consistent with the intended Defence use of the aircraft.

Where the Defence Type Certification programme intends to leverage prior certification from a recognised CAA/MAA to any extent, a CRE delta assessment is required to confirm the applicability of that prior certification to the intended Defence use. Areas where the prior certification is not entirely applicable to the Defence CRE must be addressed through further compliance demonstration evidence, inclusion of additional requirements in the TCB, or tailoring of requirements for the TCB.

GM 21.A.17A ‐ Type‐certification basis for a Military Type Certificate (MTC) or Military Restricted Type Certificate (MRTC) (AUS)

Introduction

This GM addresses the type‐certification basis for an MTC or an MRTC.

Applicable Requirements of the Airworthiness Code (see DASR 21.A.17A(a))

The type‐certification basis for an MTC or an MRTC consists of the requirements from the established airworthiness code that were effective on the date of application and were applicable for that certificate.

The effectivity date of the initial application may be changed, as per DASR 21.A.15(f)(2), when the period of validity of an application for a type certificate is exceeded, or it is evident that it will be exceeded, and the applicant requests an extension; see DASR GM 21.A.15(e) and (f).

The certification basis is then revised accordingly.

Elect to Comply (see DASR 21.A.17A(a)(1))

It is also possible for an applicant to elect to comply with an airworthiness requirement that entered into force after the date on which the applicant has submitted the application.

The Authority will assess whether the proposed certification basis is appropriate to ensure that the ‘elect to comply’ proposal includes any other airworthiness requirements that are ‘directly related’ to one or several of the airworthiness requirements in it. Directly related airworthiness requirements are those that are deemed to contribute to the same safety objective by building on each other’s requirements, addressing complementary aspects of the same safety concern, etc. Typically, they are adopted simultaneously with, or prior to, the airworthiness requirements with which the applicant has elected to comply.

Equivalent Level of Safety (see DASR 21.A.17A(a)(2))

In cases in which the applicable airworthiness requirements cannot be literally complied with, either fully or in part, the Authority may accept a suitable alternative which provides an equivalent level of safety through the use of appropriate compensating factors.

In cases in which the requirements contain not only objectives but also prescriptive parts, an equivalent level of safety may be accepted if:

the objectives are met by designs or features other than those required in the airworthiness requirements; or

suitable compensating factors are proposed.

Exceptions (see DASR 21.A.17A(a)(3))

If the intent of the airworthiness requirements defined in DASR 21.A.17A(a) or Special Conditions defined in 21.A.17A(b) cannot be met, the Authority may accept an Exception against the airworthiness requirement in order to account for military capability imperatives. In accordance with DASR GR.80(c), these exceptions must be underpinned by sound risk management which demonstrates a credible and defensible level of safety has been achieved for the intended military operations. ‘Sound risk management’ requires an understanding of the risk associated with the compliance shortfall, management of that risk in accordance with DASR SMS.A.25(b)2.2, and documentation of that risk management via an Airworthiness Issue Paper or equivalent.

Note: While DASR 21.A.17A(a)(3) links the issue of an MTC to compliance with the relevant essential requirements of Annex A to DASP Manual Volume 1 Chapter 4, the Authority may issue MTC to aircraft that do not meet those requirements when tailoring has been agreed via a Military Certification Review Item. See DASR AMC 21.A.21(a).

Special Conditions (see DASR 21.A.16B)

The Authority may also prescribe special conditions in accordance with DASR 21.A.16B. Guidance on special conditions is provided in DASR GM 21.A.16B, DASR GM1 21.A.16B and DASR GM2 21.A.16B.

GM 21.A.17A(a)(3) - Type-certification Basis (AUS)

The EMACC Guidebook offers guidance on how to tailor the criteria for the type-certification basis, based on the intended military use of the product.

GM2 21.A.20 - Demonstration of compliance with the type certification basis, operational suitability data certification basis and environmental protection requirements (AUS)

When leveraging prior certification by a CAA/MAA to claim part or full relief against the requirement to develop compliance evidence, the Configuration, Role and Environment (CRE) used to underpin the prior certification needs to be understood and compared to the intended Defence CRE at a detailed level. In isolation, basic comparisons of high‐level aircraft role(s), mission mix or flight profiles (as articulated in the SOIU) will usually not provide the fidelity required.

For aircraft structures and propulsion systems, the CRE in terms of configuration, and role‐related loads and environmental factors (including operating weights, altitudes, repeated manoeuvre, dynamic and gust environments) should be assessed in detail. For propulsion systems, the initial CRE assessment should follow the mission analysis requirements of the Defence Aviation Safety Design Requirements Manual (DASDRM) and DASR AMC 21.A.44(c).

GM1 21.A.20 - Compliance with the type-certification basis, operational suitability data certification basis and environmental protection requirements (where applicable) (AUS)

Full Relief from Developing Compliance Demonstration Evidence

The certification programme should document those Type Certification Basis (TCB) elements for which 'Prior Certification from another CAA/MAA' will be leveraged to demonstrate compliance against the TCB. To support the use of prior certification, the certification programme should also include how the criteria in DASR AMC 21.A.20 will be, or have been assessed.

Certifications that were granted sometime prior to the Defence acquisition can be problematic, particularly if they are from a CAA/MAA that has not been recognised by Defence. Current day assessments may not be reflective of the CAA/MAA at the time of the certification and hence present limited value to the Compliance Demonstration process. The certification programme will need to discuss these issues and document an approach to addressing the issues that is acceptable to the Authority.

Some MAAs do not use a ‘TCB like’ construct for defining the design requirements used for a particular design. Depending on the data access provisions permitted by the contracting arrangement used, full knowledge of the design requirements applied may not be possible. The certification programme will need to discuss this issue and document an approach to addressing this issue that is acceptable to the Authority

Partial Relief from Developing Compliance Demonstration Evidence

The prior certification provided by the CAA/MAA may not always be entirely applicable for the Defence Configuration, Role and Environment (CRE) (and as such may not be entirely applicable for demonstrating compliance to the Defence TCB). There are a number of reasons why this would be the case:

the prior CAA/MAA certification cannot be shown to apply for all standards specified in the Defence TCB;

The CRE assessment identified material differences between the CRE assumed by the prior certifying CAA/MAA and the intended Defence CRE (particularly applicable for those cases where civil CAA certification is being leveraged which does not cover military roles and environment); or

The CAA/MAA certification is underpinned by risk treatments that require further consideration in the Australian Work Health and Safety Act 2011 and the Work Health and Safety Regulations 2011 framework.

Known issues associated with leveraging prior certification should be documented in the certification programme, along with an agreed approach for addressing them. Possible treatments include:

Investigating if relevant additional evidence exists and obtaining that additional evidence from the design organisation;

Development of additional evidence (which will require a MDOA holder (or Authority‐ accepted equivalent));

A change to the design (either the configuration or Instructions for Continuing Airworthiness (ICA)); or

Seeking Authority agreement to amend the TCB, by adding or tailoring requirements, IAW AMC1 21.A.17A.

GM 21.A.20 ‐ Compliance demonstration process

DASR 21.A.20 applies to the compliance demonstration process for a Military Type Certificate (MTC) (or a Military Restricted Type Certificate (MRTC)) and, by cross references to DASR Part 21 Subpart D and E, to compliance demonstration processes for major changes to an MTC (see DASR 21.A.97(b)(3)) and an MSTC (see DASR 21.A.115(b)(4)).

Applicants for an MTC (or an MRTC) should apply DASR 21.A.20 in full. Applicants for a major change to an MTC (or an MSTC) are required (see DASR 21.A.97(b)(3) and DASR 21.A.115(b)(4)) to apply DASR 21.A.20 as applicable to the change.

‘As applicable to the change’ means that:

The certification programme to be followed is the one prepared for the major change or MSTC in accordance with DASR 21.A.93, as accepted by the Authority; and

The certification basis (consisting of the type‐certification basis, operational suitability data (OSD) certification basis, and the environmental protection requirements) is the one established in accordance with DASR 21.A.101.

DASR 21.A.20 also applies to major changes to an MTC or an MSTC approved by military design organisation approval (MDOA) holders under their privilege as per DASR 21.A.263(c)(8) or (9) (see also DASR 21.A.97(b)(3) and DASR 21.A.115(b)(4)). As in this case there is no application and no involvement of the Authority, DASR 21.A.20 should be applied with the following adaptions:

the certification programme to be followed, including the certification basis and the detailed means of compliance, should be almost identical to the one accepted by the Authority for a major change or an MSTC when approved for the scope of the privilege as per DASR 21.A.263(c)(8) or (9); it may differ in some aspects (e.g. the detailed description of the changes), but it should be shown to remain in the frame of the corresponding justification document; and

the means by which such compliance has been demonstrated (see DASR 21.A.20(a)) and the final declaration of compliance (see DASR 21.A.20(e)) should be kept on record and submitted to the Authority only if requested during its DOA continued surveillance process.

GM 21.A.20(b) Reporting on the compliance demonstration process

The applicant should report to the Authority any unexpected difficulty or event encountered during the compliance demonstration that invalidates or appreciably affects the assumptions previously made, for example:

An increase in the severity of the consequences of a certain condition (e.g. failure mode) of the product;

Significantly reduced margin(s) for the ‘pass–fail’ criteria of the compliance demonstration;

Changes to the test sequences and conditions that are not in line with the certification specifications or guidance;

An unusual interpretation of the results of the compliance demonstration; and

Any significant failure or finding resulting from the tests performed as per DASR 21.A.33 or DASR 21.A.35.

The applicant should also evaluate whether the unexpected difficulty or event encountered will impact on the certification programme and, if necessary, amend it as per DASR 21.A.15(c).

GM 21.A.20(d) - Final statement

All compliance demonstrations in accordance with the certification programme, including all the inspections and tests in accordance with DASR 21.A.33 and all flight tests in accordance with DASR 21.A.35, should be completed before the issuance of the final statement of compliance required by DASR 21.A.20(d).

If so agreed by the Authority, some compliance documentation may be produced after the issuance of the final statement of compliance required by 21.A.20(d).

‘No feature or characteristics’ in DASR 21.A.20(d)2 means the following: while every effort is made to address in the applicable certification basis all the risks to product safety or to the environment that may be caused by the product, experience shows that safety‐related events may occur with products in service, even though compliance with the certification basis is fully demonstrated. One of the reasons may be that some existing risks are not properly addressed in the certification basis. Therefore, the applicant has to declare that they have not identified any such features or characteristics.

DASR 21.A.20 also applies by reference to minor changes, in which case the risk to product safety or to environmental protection is quite low. Nevertheless, minor changes should not be approved if either the applicant/military design organisation approval (MDOA) holder approving minor changes under their privileges, or the Authority, is aware of a feature or characteristic that may make the product unsafe for the uses for which certification is requested.

Where a recognised certified design has been leveraged to relieve the applicant from developing compliance demonstration evidence, the basis upon which the declaration of compliance is made is the applicant’s completion of the requirements of DASR AMC 21.A.20.

GM 21.A.21(a)(3)(A) ‐ Issue of type‐certificates for engines and propellers (AUS)

While an Australian MTC will be issued for every aircraft type to be Defence registered, Australian MTCs will not ordinarily be issued for engines and propellers of Defence registered aircraft unless exceptional circumstances exist. Exceptional circumstances include, but are not limited to, an engine or propeller not previously type certified under another recognised aviation authority, or where Defence elects to manage the engine or propeller configuration independently from other users of the same engine or propeller.

GM 21.A.33(d) ‐ Inspections and tests

The applicant should inform the Authority sufficiently in advance about the execution of inspections and tests that are used for compliance demonstration purposes unless the Authority has explicitly excluded these inspections and tests from its involvement.

Additionally, the applicant may propose to the Authority to perform or witness flight or other tests of particular aspects of the product during its development and before the type design is fully defined. However, before the Authority performs or witnesses any flight test, the applicant should ensure by appropriate means that the design is mature enough so that no features of the product preclude the safe conduct of the evaluation requested.

The Authority may require any such tests to be repeated once the type design is fully defined to ensure that subsequent changes have not adversely affected the conclusions from any earlier evaluation.

GM1 21.A.35 – Flight Tests (AUS)

In-service flight test activities are covered under Subpart P – Military Permit to Fly, and DASR GM 21.A.35 establishes the approval arrangements for MPTFs according to category, see Categories of Flight TestsCategories of Flight Tests.

GM 21.A.35 - Flight Tests

Detailed material on flight testing is included in the applicable airworthiness codes and associated guidance material.

GM 21.A.35(b)(2) - Objective and content of function and reliability testing

Objective

The objective of this testing is to expose the aircraft to the variety of uses, including training, that are likely to occur when in routine service to provide an assurance that it performs its intended functions to the standard required for certification and should continue to do so in service.

Content of function and reliability testing

The testing should cover both routine operations and some simulation of abnormal conditions. The details of the programme should be agreed with the Authority prior to commencement of testing.

It may be possible to combine this testing with any required to demonstrate compliance with the applicable type-certification basis or certification basis for operational suitability data. This will be agreed on a case-by-case basis with the Authority.

Where possible, testing conditions should be defined with the co-operation of an operating organisation.

A substantial proportion of the flying should be on a single aircraft. The flying should be carried out to a continuous schedule on an aircraft that is very close to the final type design, operated as though it were in service and should include a range of representative ambient operating conditions and airfields.

GM 21.A.35(f)(1) - Flying time for function and reliability testing

All flying carried out with engines and associated systems not significantly different from the final type-certificate standard may count towards the 300 hours airframe flight time required by DASR 21.A.35(f)(1). At least 150 of the 300 flying hours is to be conducted on a dedicated production configured aircraft. The requirement for 300 hours relevant flight time whenever a new turbine engine is incorporated applies regardless of whether the airframe/engine combination is subject to a new type-certificate or is to be certificated as a change or supplement to an existing type-certificate.

GM 21.A.35(f)(2) - Flying time for function and reliability testing

All flying carried out on an aircraft not significantly different from the final type design may count towards the 150 hours airframe flight time required by DASR 21.A.35(f)(2).

GM 21.A.M42 - Integration

The following principles of military type-certification should be applied when determining the responsibilities for integration. 

The certification of products, including their parts and appliances, is based on the demonstration of compliance (refer to DASR 21.A.20 and 21.A.303) with the applicable type-certification basis (DASR 21.A.17A), the certification basis for operational suitability data (DASR 21.A.17B)and the specified environmental protection requirements (DASR 21.A.18). 

The responsibility for the integration of products installed on an aircraft follows the hierarchy as specified in DASR 21.A.21(a)(3); 

The responsibility for the certification and integration of Parts and Appliances (refer also to DASR 21.A.303(a)), which are to be approved under the procedures of Subparts B or D, lies in principle with the type certificate holder of the respective product;

The responsibility for the certification and integration of a part of a product covered by a supplemental type-certificate remains with the holder of the supplemental type-certificate. 

The approval of parts and appliances within the scope of a Australian Military Technical Standard Order Authorisation (AUSMTSOA) according to the procedures of Subpart O (refer to DASR 21.A.303(b)) is based on the demonstration of compliance with the specified technical performance and airworthiness requirements by the respective manufacturer / holder of the AUSMTSO authorisation. The responsibility for integration of these items on the aircraft lies with the aircraft type certificate holder by demonstrating that the aircraft, with any generic article authorised to the same technical and airworthiness standards is and remains compliant with the applicable type-certification basis, the certification basis for operational suitability data and the specified environmental protection requirements.

GM 21.A.44 - Obligations of the holder (AUS)

DASR GM 21.A.14 defines the role of a government MTC holder organisation in holding all DASA issued MTC / MRTC and subsequent major design change approval, STCs and major repair design approvals.

GM 21.A.55 - Record keeping (AUS)

Records should be retained for at least two years after the removal from service of the last aircraft of the type certified.

GM 21.A.61 - Instructions for Continuing Airworthiness (AUS)

Instructions for Continuing Airworthiness (ICA) details the methods, inspections, processes, and procedures necessary for the air operator to keep aircraft and / or engine, propeller, parts and appliances airworthy during its intended life.

The contents of ICA can be divided into two categories:

an approved airworthiness limitations (AwL) section as defined by the applicable airworthiness codes during the certification process, which forms part of the type design / type-certificate (DASR 21.A.31(a)(3) and DASR 21.A.41):

any limitations determined through the certification of the product, and instructions on how to determine that these limits have been exceeded.

any inspection, servicing or maintenance actions determined to be necessary by the certification process.

sections that do not contain approved data from the certification process and are not considered as part of type design/type-certificate:

any inspection or troubleshooting actions determined to be necessary to establish the nature of faults and the necessary remedial actions.

sufficient general information on the operation of the product to enable an understanding of the instructions in paragraphs (a)(i), (a)(ii), and (b)(i) above.

GM 21.A.90A – Scope

The term ‘changes to the type certificate’ is consistently used in DASR 21 Section A Subpart D and E, as well as in the related AMC and GM. This term does not refer to changing the document that reflects the Military Type Certificate (MTC) but to the elements of the MTC as defined in DASR 21.A.41. It means that the processes for the approval of changes, as described in the said two Subparts, do not only apply to changes to the type design, but may also apply to changes to:

the operating limitations;

the type certificate data sheet (TCDS) for airworthiness and, where applicable, emissions;

the applicable type‐certification basis and environmental protection requirements with which the applicant has to demonstrate compliance;

any other conditions or limitations prescribed for the product by the Authority;

the applicable operational suitability data (OSD) certification basis;

the OSD; and

where applicable the TCDS for noise.

NOTE: OSD is only applicable to aircraft TCs and not to engine or propeller TCs. Therefore, changes to OSD are only relevant for changes to aircraft TCs. 

GM 21.A.91 - Classification of changes to a Military Type Certificate (MTC)

1.       Purpose of classification

1.1    Classification of changes to a Military Type Certificate (MTC) into 'MAJOR' or 'MINOR' is to determine the approval route to be followed in DASR 21 Section A Subpart D, ie either DASR 21.A.95 or DASR 21.A.97, or alternatively whether application and approval has to be made in accordance with DASR 21 Section A Subpart E

2.       Introduction

2.1    DASR 21.A.91 proposes criteria for the classification of changes to an MTC as minor and major.

This GM is intended to provide guidance on the term 'appreciable effect' affecting the airworthiness of the product or affecting any of the other characteristics mentioned in DASR 21.A.91, where 'airworthiness' is interpreted in the context of a product in conformity with type design and in condition for safe operation. It provides complementary guidelines to assess a change to the MTC in order to fulfil the requirements of DASR 21.A.91 and DASR 21.A.117 where classification is the first step of a procedure.

 NOTE: For classification of Repairs see DASR GM 21.A.435(a). 

Although this GM provides guidance on the classification of major changes, as opposed to minor changes as defined in DASR 21.A.91, the GM and DASR 21.A.91 are deemed entirely compatible.

 2.2    For an AUSMTSO authorisation, DASR 21.A.611 gives specific additional requirements for design changes to AUSMTSO articles.

 For APU, this GM 21.A.91 is to be used.

 3.      Assessment of a design change for classification

 3.1    Changes to the MTC

 DASR 21.A.91 addresses all changes to any of the aspects of an MTC. This includes changes to a type design, as defined in DASR 21.A.31, as well as to the other constituents of an MTC, as defined in DASR 21.A.41.

3.2     (Reserved)

3.3    Classification Process (see diagram in Appendix A to GM 21.A.91Appendix A to GM 21.A.91) 

DASR 21.A.91 requires all changes to be classified as either major or minor, using the criteria of DASR 21.A.91 and the complementary guidance of paragraph 3.4. 

Wherever there is doubt as to the classification of a change, the Authority is to be consulted for clarification.

When the strict application of the paragraph 3.4 criteria results in a major classification, the applicant may request reclassification, if justified, and the Authority could take the responsibility in reclassifying the change.

A simple design change planned to be mandated by an airworthiness directive may be reclassified minor due to the involvement of the Authority in the continued airworthiness process when this is agreed between the Authority and the MDOA holder.

The reasons for a classification decision should be recorded.

3.4    Complementary guidance for classification of changes

A change to the MTC is judged to have an ‘appreciable effect on the mass, balance, structural strength, reliability, operational characteristics, noise, fuel venting, exhaust emission, operational suitability or other characteristics affecting the airworthiness, or environmental protection, or operational suitability of the product’ and, therefore, should be classified as major, in particular but not only, when one or more of the following conditions are met:

Where the change requires an adjustment of the type‐certification basis or the OSD certification basis  (such as special conditions, equivalent safety findings or exceptions) other than electing to comply with airworthiness requirements that are derived from a later amendment to an airworthiness code;

Where the applicant proposes a new interpretation of the airworthiness requirements used for the type certification basis that has not been published as AMC material or otherwise agreed with the Authority;

Where the demonstration of compliance uses methods that have not been previously accepted as appropriate for the nature of the change;

Where the extent of new substantiation data necessary to comply with the applicable airworthiness requirements and the degree to which the original substantiation data has to be re-assessed and re-evaluated is considerable;

Where the change alters the airworthiness limitations or the operating limitations;

Where the change is made mandatory by an airworthiness directive or the change is the terminating action of an airworthiness directive (reference DASR 21.A.3B), see NOTE 1; and

Where the change introduces or affects functions where the failure effect is classified catastrophic or hazardous.

NOTE 1: A change previously classified as minor and approved prior to the airworthiness directive issuance decision needs no reclassification. However, the Authority retains the right to review the change and reclassify/reapprove it if found necessary.

NOTE 2: The conditions listed in (a) through (g) above are an explanation of the criteria noted in DASR 21.A.91.

For an understanding of how to apply the above conditions, it is useful to take note of the examples given in Appendix A to GM 21.A.91Appendix A to GM 21.A.91 Appendix A to GM 21.A.91Appendix A to GM 21.A.91

3.5    Complementary guidance on the classification of changes to OSD

This paragraph provides firstly general guidance on minor OSD change classification, and secondly additional guidance specific to each OSD constituent.

Changes to OSD are considered minor when they:

incorporate optional information (representing improvements/enhancements);

provide clarifications, interpretations, definitions or advisory text; or

do not change the intent of the OSD document, e.g. changes to:

 titles, numbering, formatting, applicability;

order, sequence, pagination; or

sketches, figures, units of measurement, and correction of editorial mistakes such as: spelling; or reference numbers.

Given the structure and individual intent of the separate OSD constituents, the interpretation of ‘appreciable’ is also affected by the specific nature of the applicable airworthiness codes or standards (e.g. EASA certification specifications (CS)) for that constituent. Therefore, specific guidance on each of the OSD constituents should be consulted. The guidance listed in (a) to (e) below assumes that EASA CS-MMEL, CS-FCD, CS-CCD, CS-SIMD and CS-MCSD are used. It should be adopted for other OSD specific airworthiness codes or standards.

(a) Master minimum equipment list (MMEL)

A change to the MMEL is judged to have an ‘appreciable effect on the operational suitability of the aircraft’ and, therefore, should be classified as major, in particular but not only when one or more of the following conditions are met:

where the change requires an adjustment of the OSD certification basis;

where the applicant proposes changes to the means of compliance with the requirements used for the OSD certification basis (i.e. MMEL safety methodology);

where the extent of substantiation data and the degree to which the substantiation data has to be assessed and evaluated is considerable, in particular but not only when:

the substantiation data involving the review of failure conditions that are classified as hazardous or catastrophic has to be evaluated;

the assessment of the failure effects (including next worst failure/event effects) on crew workload and the applicable crew procedures has to be evaluated; or

the capability of the aircraft to perform types of operation (e.g. Defence Long Range Operations (DLRO), instrument flight rules (IFR)) under MMEL is extended.

A change to the MMEL is judged not to have an ‘appreciable effect on the operational suitability of the aircraft’ and, therefore, should be classified as minor, in particular but not only when one or more of the following conditions are met:
Modifications to an existing item when:

the change only corresponds to the applicability of an item for configuration management purposes;

the change corresponds to the removal of an item;

the change corresponds to the increase in the number of items required for dispatch; and

the change corresponds to a reduction in the rectification interval of an item.
Addition of a new item when:

it is considered as non-safety-related (refer to CS-MMEL, GM2 MMEL.110); or.

it is indicated as eligible for minor change classification in 1 to GM1 CS-MMEL-145.

Flight crew data (FCD)

FCD change related to change to the type design
When classifying the FCD change as minor or major, the method of CS-FCD, Subpart D could be used, using the following steps.

An analysis should be performed to assess the change impact on the FCD through the allocation of difference levels realised with operator difference requirement (ODR) tables as per CS FCD.400. In this case, the base aircraft is the aircraft without the type design change, whereas the candidate aircraft is the aircraft which includes the type design change.

If a no more than level B difference is assigned for training, checking and currency for the candidate aircraft, the related FCD change should be classified as minor.

If a difference level C, D or E for training, checking and currency is assigned to the candidate aircraft, the related FCD change should be classified as major.

Notwithstanding the above, the change to FCD should be classified as major when a T1 or T2 test is found necessary by the applicant to confirm that the aircraft with the type design change is not a new type for pilot type rating.

Stand-alone changes to FCD are not related to any type design changes. They may be triggered for example by in-service experience or by the introduction of data at the request of the applicant after type certification.

Introduction of credits in training, checking or currency should be classified as major. Example: addition of further-differences training, common take-off and landing credits, etc.

Stand-alone changes to FCD that correspond to a change of the intent of a data should be classified as major. Example: addition of a training area of special emphasis (TASE) or prerequisite, expansion of a TASE.

Cabin crew data (CCD)

OSD change related to change to the type design
When classifying the OSD CCD change as minor or major, the method from CS-CCD, Subpart B should be used.

An analysis should be performed to assess the change impact on the OSD CCD through the identification of the difference and its impact on operation in the aircraft difference table (ADT) as per CS CCD.200. In this case, the base aircraft is the aircraft without the type design change, whereas the candidate aircraft is the aircraft which includes the type design change.

If the difference has no impact on the operation of an element of the ADT for the candidate aircraft, the related OSD CCD change should be classified as minor.

If the difference has an impact on the operation of an element of the ADT for the candidate aircraft, the related OSD CCD change should be classified as major.

Notwithstanding the above, the change to OSD CCD should be classified as major when an ADT analysis is found necessary by the applicant to confirm that the aircraft with the type design change is not a new type for cabin crew.

Stand-alone changes to OSD CCD are not related to any type design changes. They may be triggered for example by in-service experience or by the introduction of data at the request of the applicant after type certification.

Stand-alone changes to cabin aspects of special emphasis (CASE) should be classified as major. Example: addition of further CASE, expansion of CASE.

When classifying stand-alone changes to type-specific data for cabin crew the method from CS-CCD, Subpart B should be used. An analysis should be performed to assess the change impact on the type-specific data through the identification of the difference and its impact on operation in the ADT as per CS CCD.200.

If the change does not concern a determination element of CS CCD.205, the stand-alone change should be classified as minor.

If the change has no impact on the operation of an element of the ADT, the stand-alone change should be classified as minor.

If the change has an impact on the operation of an element of the ADT, the stand-alone change should be classified as major.

Simulator data (SIMD)

The OSD constituent ‘simulator data’ does not include the data package that is necessary to build the simulator. It includes only the definition of the scope of validation source data to support the objective qualification of a simulator. So, when this guidance discusses changes to ‘simulator data’, this concerns only changes to the ‘definition of scope of validation source data’ and not changes to the data package.

A change to the SIMD should be classified as major, in particular but not only when one or more of the following conditions are met:

when a change to the SIMD introduces validation source data from an engineering platform where the process to derive such data has not been audited by the Authority in the initial SIMD approval; or

when the process to derive validation source data from an engineering platform is changed.

A change to the SIMD could be classified as minor, in particular but not only when one or more of the following conditions are met:

changes to engineering validation data independent of the aircraft due to improvements or corrections in simulation modelling (e.g. aerodynamics, propulsion);

configuration changes to the aircraft where the process to derive validation source data from an engineering platform is unchanged;

changes to validation source data by using better, more applicable flight test data; or

editorial changes to the validation data roadmap (VDR).

Maintenance certifying staff data (MCSD)

[Reserved]
 

3.6    Complementary guidance for the classification of changes to aircraft flight manuals (AFMs)

The following changes to the AFM are deemed to be minor:

revisions to the AFM associated with changes to the type design that are classified as minor in accordance with DASR 21.A.91;

revisions to the AFM that are not associated with changes to the type design (also identified as stand‐alone revisions) which fall into one of the following categories:

changes to limitations or procedures that remain within already certified limits (e.g. weight, structural data, noise, etc.);

consolidation of two or more previously approved and compatible AFMs into one, or the compilation of different parts taken from previously approved and compatible AFMs that are directly applicable to the individual aircraft (customisation); and

the introduction into a given AFM of compatible and previously approved AFM amendments, revisions, appendices or supplements; and

administrative revisions to the AFM, defined as follows:

for the AFMs issued by the MTC holder:

editorial revisions or corrections to the AFM;

changes to parts of the AFM that do not require approval by the Authority;

conversions of previous Authority approved combinations of units of measurement added to the AFM in a previously approved manner;

the addition of aircraft serial numbers to an existing AFM where the aircraft configuration, as related to the AFM, is identical to the configuration of aircraft already covered by that AFM;

the removal of references to aircraft serial numbers no longer applicable to that AFM;

for AFM supplements issued by MSTC holders:

editorial revisions or corrections to the AFM supplement;

changes to parts of the AFM supplement that are not required to be approved by the Authority;

conversions of previous Authority approved combinations of units of measurement added to the AFM supplement in a previously approved manner;

the addition of aircraft serial numbers to an existing AFM supplement where the aircraft configuration, as related to the AFM supplement, is identical to that of the aircraft already in that AFM supplement;

‘identical’ means here that all the aircraft have to belong to the same type and model/variant;

the addition of a new MSTC to an existing AFM supplement, when this supplement is fully applicable to the new MSTC;

the removal of references to aircraft serial numbers that are no longer applicable to that AFM supplement.        

GM 21.A.92 (a) - Eligibility to apply for approval of a major change to a type-certificate

The expression “Only the type-certificate holder may apply for approval of a major change to a type-certificate under this Subpart” includes any person or organisation acting on behalf of the type-certificate holder in accordance with DASR 21.A.2, subject to the arrangements with the Holder.

GM1 to 21.A.93(b) ‐ Software aspects of a Certification Programme (AUS)

The certification programme may include software certification requirements for Major changes to type design. The Authority encourages applicants to develop a Plan for Software Aspects of Certification (PSAC), or equivalent document, and provide it as an enclosure to the certification programme.

GM 21.A.93(b) ‐ 'Simple' Major Changes (AUS)

For a 'simple' major change, the certification programme may be provided with the final application for approval.

A 'simple' major change is a change which does not require long or complex compliance demonstration activities, where the proposal for the Authority Level of Involvement (based on DASR 21.A.93(b)3(iii)) is nil. A change which requires tailoring of the certification basis would not normally be considered simple, unless the tailoring can be assessed without an understanding of the specific programme (for example, inclusion of a Special Condition covering DASDRM requirements for a capability or technology not currently covered in the TCB). Tailoring must be formally agreed with the Authority before submission of the final application and the associated declaration of compliance.

Some examples of major changes that may be considered 'simple' are:

Changes to Airworthiness Limitations (AwLs) and Certification Maintenance Requirements (CMRs) or revised OEM source publications previously certified by a recognised CAA/MAA

Changes to the Operating Limitations of an MTC previously certified by a recognised CAA/MAA.

Other major changes previously certified by a recognised CAA/MAA, where there are no CRE deltas

While the above examples would typically be considered 'simple' the Authority may, on presentation of an application, identify a requirement for LoI or otherwise identify an issue with the presented certification programme. These issues may result in additional work and/or a requirement for the certification programme to be separated from the final application.

GM 21.A.93(b)(2) ‐ Type‐certification Basis for a change to a type‐certificate (AUS)

The type‐certification basis referenced in DASR 21.A.93(b)2 is established through DASR 21.A.95 for a minor change and DASR 21.A.101 for a major change. DASR 21.A.95 and DASR 21.A.101 state that the existing certification basis established in the type certificate is considered adequate for 'minor' and non‐significant 'major' changes. However, Australia’s Work Health and Safety Act (Commonwealth) 2011 (WHS Act), levies additional obligations on designers, namely to exercise ‘reasonable knowledge’ when determining that any risk inherent in designs has been minimised So Far As is Reasonably Practicable (SFARP). Updates to applicable standards may provide insight into hazards and potential controls that are not identified in the version of the standards prescribed in the existing aircraft’s type certificate. The requirements prescribed in the Defence Aviation Safety Design Requirements Manual (DASDRM) provide a source of requirements and standards that can assist engineers to satisfy their obligation to exercise reasonable knowledge of hazards and associated controls in aircraft design.

GM 21.A.93(b)(3)(iii) ‐ Level of Involvement (AUS)

For acceptable means of compliance regarding proposal and determination of LoI see AMC 21.A.15(b)(6).

GM 21.A.93(c) ‐ Period of validity for the application

For guidance on the determination of the period of validity for the application, refer to GM 21.A.15(e) and (f).

GM 21.A.95(b) ‐ Requirements for the approval of a minor change

The level of detail of the documents that are referred to in DASR 21.A.93(b) should be the same regardless of whether the change is approved by the Authority or under a Military Design Organisation Approval (MDOA) privilege, to allow the change to be assessed in the frame of the MDOA surveillance.

GM 21.A.97(b) - Requirements for the approval of a major change

The level of detail of the documents that are referred to in DASR 21.A.93(b) should be the same regardless of whether the change is approved by the Authority or under a military design organisation approval (MDOA) privilege, to allow the change to be assessed in the frame of the MDOA surveillance.

GM 21.A.101 ‐ Establishing the certification basis of changed aeronautical products

This guidance material (GM) provides guidance for the application of the ‘Changed Product Rule (CPR)’, pursuant to DASR 21.A.101, Type‐certification basis and environmental protection requirements for a major change to a type‐certificate, and DASR 21.A.19, Changes requiring a new type‐certificate, for changes made to type‐certified aeronautical products.

1.          INTRODUCTION

1.1         Purpose.

This GM provides guidance for establishing the certification basis for changed aeronautical products pursuant to DASR 21.A.101, Type‐certification basis and environmental protection requirements for a major change to a type‐certificate. The guidance is also intended to help applicants and approved design organisations to determine whether it will be necessary to apply for a new Military Type Certificate (MTC) under DASR 21.A.19, Changes requiring a new type certificate. The guidance describes the process for establishing the certification basis for a change to an MTC, for a Military Supplemental Type Certificate (MSTC), or for a change to an MSTC, detailing the requirements (evaluations, classifications, and decisions) throughout the process.

1.2        Applicability.

1.2.1    This GM is for an applicant that applies for changes to MTCs under Subpart D, for MSTCs, or changes to MSTCs under Subpart E, or for changes to Australian Military Technical Standard Order (AUSMTSO) authorisations for auxiliary power units (APUs) under Subpart O.

1.2.2    This GM applies to major changes under DASR 21.A.101 for aeronautical products certified under Part 21, and the airworthiness requirements applicable to the changed product. References to ‘change’ include the change and areas affected by the change pursuant to DASR 21.A.101.

1.2.3    (Reserved)

1.2.4    This GM also applies to changes to restricted type certificates.

1.2.5    The term ‘aeronautical product’, or ‘product’, means a type‐certified aircraft, aircraft engine, or propeller and, for the purpose of this GM, an AUSMTSO approved APU.

1.2.6    This GM primarily provides guidance for the designation of applicable airworthiness requirements for the type-certification basis for the changed product. However, portions of this GM, as specified in GM1 21.A.101(g), can be applied by analogy to establish the operational suitability data (OSD) certification basis for the changed product. This GM is not intended to be used to determine the applicable environmental protection requirements (aircraft noise, fuel venting, and engine exhaust emissions and aeroplane CO2 emissions requirements) for changed products, as they are designated by the Authority through DASR 21.A.18.

1.2.7    This GM is not mandatory. This GM describes an acceptable means, but not the only means, to comply with DASR 21.A.101. However, an applicant who uses the means described in this GM must follow it entirely.

1.3    Reserved.

1.4    GM Content.

This GM contains 5 chapters and 10 appendices.

1.4.1    This chapter clarifies the purpose of this GM, describes its content, specifies the intended audience affected by this GM, clarifies which changes are within the scope of this GM, and references the definitions and terminology used in this GM.

1.4.2    Chapter 2 provides a general overview of DASR 21.A.101 and DASR 21.A.19, clarifies the main principles and safety objectives, and directs an applicant to the applicable guidance contained in subsequent chapters of this GM.

1.4.3    Chapter 3 contains guidance for the implementation of DASR 21.A.101(b) to establish the certification basis for changed aeronautical products. It describes in detail the various steps for developing the certification basis, which is a process that applies to all changes to aeronautical products. Chapter 3 also addresses the DASR 21.A.19 considerations for identifying the conditions under which an applicant for a change is required to submit an application for a new MTC, and it provides guidance regarding the stage of the process at which this assessment is performed.

1.4.4    Chapter 4 is reserved.

1.4.5    Chapter 5 contains considerations for:

—    design‐related operating requirements,
—    defining a baseline product,
—    using special conditions under DASR 21.A.101(d),
—    documenting revisions to the MTC basis,
—    incorporating MSTCs into the type design,
—    removing changes,
—    determining a certification basis after removing an approved change, and
—    sequential changes.

1.4.6    Appendix A contains a reference to examples of typical type design changes for products (small aeroplanes, large aeroplanes, rotorcraft, engines, and propellers), as categorised by the European Union Aviation Safety Agency (EASA) into individual tables according to the classifications of design change: ‘substantial’, ‘significant’, and ‘not significant’.

1.4.7     Appendix B contains the application chart for applying the DASR 21.A.101 process.

1.4.8     Appendix C contains a reference to the method proposed by the European Union Aviation Safety Agency (EASA) for determining the changed and affected areas of a product.

1.4.9     Appendix D contains additional guidance on affected areas that is not discussed in other parts of this GM.

1.4.10   Appendix E provides reference and military specific considerations for evaluating the ‘impracticality’ exception in the requirement.

1.4.11   Appendix F provides guidance and reference to examples on the use of relevant service experience in the certification process as one way to demonstrate that a later amendment may not contribute materially to the level of safety, allowing the use of earlier airworthiness codes or specifications.

1.4.12   Appendix G provides guidance on the structure of a CPR decision record.

1.4.13   Appendix H provides a reference to examples of documenting a proposed certification basis list.

1.4.14   Appendix I lists DASR 21 requirements related to this GM.

1.4.15   Appendix J lists the definitions and terminology applicable for the application of the changed product rule.

1.5    Terms Used in this GM.

1.5.1    The following terms are used interchangeably and have the same meaning: ‘specifications’, ‘standards’, ‘airworthiness requirements’, 'requirements', ‘airworthiness codes‘ and ‘certification standards’ . They refer to the elements of the type‐certification basis for airworthiness. Examples of such elements are EASA CS, FAA FAR, Mil Hdbk, JSSG, STANAG, Def-STAN, etc., as declared applicable by the Authority. See the Defence Aviation Safety Design Requirements Manual (DASDRM) Section 1 Chapter 1 for discussion on the differences between requirements and standards.

1.5.2    The term ‘certification basis’ refers to the type‐certification basis for airworthiness provided for in DASR 21.A.17A.

1.6    For more terms, consult Appendix J.

2.          OVERVIEW OF DASR 21.A.19 AND DASR 21.A.101

2.1        DASR 21.A.19.

2.1.1    DASR 21.A.19 requires an applicant to apply for a new MTC for a changed product if the Authority finds that the change to the design, power, thrust, or weight is so extensive that a substantially complete investigation of compliance with the applicable type‐certification basis is required.

2.1.2    Changes that require a substantial re‐evaluation of the compliance findings of the product are referred to as ‘substantial changes’. For guidance, see paragraph 3.3 in Chapter 3 of this GM. Appendix A of this GM provides a reference to examples of changes that will require a new TC for aircraft classes used in civil aviation.

2.1.3    If the Authority determines through DASR 21.A.19 that a proposed change does not require a new MTC, see DASR 21.A.101 for the applicable requirements to develop the certification basis for the proposed change. For guidance, see Chapter 3 and the examples referred to in Appendix A  of this GM.

2.2        DASR 21.A.101.

2.2.1    DASR 21.A.101(a).

DASR 21.A.101(a) requires a change to an MTC, and the areas affected by the change to comply with the airworthiness requirements that are applicable to the changed product and that are in effect on the date of application for the change (i.e. the latest airworthiness requirements in effect at the time of application), unless the change meets the criteria for the exceptions identified in DASR 21.A.101(b), or unless an applicant chooses to comply with amendments of the airworthiness requirements that became effective after the date of application in accordance with DASR 21.A.101(f). The intent of DASR 21.A.101 is to enhance safety by incorporating the latest requirements into the certification basis for the changed product to the greatest extent practicable.

2.2.2    DASR 21.A.101(b).

DASR 21.A.101(b) pertains to when an applicant may show that a changed product complies with an earlier amendment of an airworthiness requirement, provided that the earlier amendment is considered to be adequate and meets the criteria in DASR 21.A.101(b)(1), DASR 21.A.101(b)(2), or DASR 21.A.101(b)(3). When changes involve features or characteristics that are novel and unusual in comparison with the airworthiness standards at the proposed amendment, more recent airworthiness standards and/or special conditions will be applied for these features.

Compliance with earlier amendments of the airworthiness requirements may be considered in accordance with DASR 21.A.101(b), when:

a change is not significant (see DASR 21.A.101(b)(1));

an area, system, part or appliance is not affected by the change (see DASR 21.A.101(b)(2));

compliance with a later amendment for a significant change does not contribute materially to the level of safety (see DASR 21.A.101(b)(3)); or

compliance with the latest amendment would be impractical (see DASR 21.A.101(b)(3)).

Earlier amendments may not precede the amendment level of the certification basis of the identified baseline product.

DASR 21.A.101(b)(1)(i) and DASR 21.A.101(b)(ii) pertain to changes that meet the automatic criteria where the change is significant.

2.2.3    (Reserved)

2.2.4    DASR 21.A.101(d).

DASR 21.A.101(d) provides for the use of special conditions, under DASR 21.A.16B, when the proposed certification basis and any later airworthiness requirements do not provide adequate standards for the proposed change because of a novel or unusual design feature.

2.2.5    DASR 21.A.101(e)

DASR 21.A.101(e) provides the basis under which an applicant may propose to certify a change and the areas affected by the change against alternative requirements to those established under 21.A.101(a) and 21.A.101(b).

2.2.6    DASR 21.A.101(f).

DASR 21.A.101(f) requires that if an applicant chooses (elects) to comply with an airworthiness requirement that is effective after the filing of the application for a change to a MTC, the applicant shall also comply with any other airworthiness requirements that the Authority finds are directly related. The airworthiness requirements which are directly related must be, for the purpose of compliance demonstration, considered together at the same amendment level to be consistent.

2.2.7    DASR 21.A.101(g).

DASR 21.A.101(g) pertains to the designation of the applicable OSD certification basis when the application for a change to a type certificate for an aircraft includes, or is supplemented after the initial application to include, changes to the OSD. It implies that the same requirements of paragraphs (a) and (f) that are applicable to the establishment of the airworthiness type-certification basis also apply to the establishment of the OSD certification basis. For specific guidance, see DASR GM1 21.A.101(g).
 

3.          PROCESS FOR ESTABLISHING THE CERTIFICATION BASIS FOR CHANGED PRODUCTS

3.1        Overview.

3.1.1    The applicant and the Authority both have responsibilities under DASR 21.A.101(a) and DASR 21.A.101(b). As an applicant for the certification of a change, the applicant must demonstrate that the change and areas affected by the change comply with the latest applicable airworthiness requirements unless the applicant proposes exception(s) under DASR 21.A.101(b). An applicant proposing exception(s) should make a preliminary classification whether the change is ‘significant’ or ‘not significant’, and propose an appropriate certification basis. The Authority is responsible for determining whether the applicant’s classification of the change, and proposal for the certification basis, are consistent with the applicable rules and their interpretation. The Authority determination does not depend on whether the MTC holder or applicant for an MSTC is originating the change. The certification basis can vary depending on the magnitude and scope of the change. The steps below present a streamlined approach for making this determination.

3.1.2    The tables referred to in appendix A of this GM are examples of classifications of typical type design changes. See paragraph 3.6.3 of this chapter for instructions on how to use those tables.

3.1.3    The following steps in conjunction with the flow chart in Figure 3‐1 of this GM can be used to develop the appropriate certification basis for the change. For clarification, the change discussed in the flow chart also includes areas affected by the change. See paragraph 3.9.1 of this GM for guidance about affected areas.

Figure 3‐1. Developing a Proposed Certification Basis for a Changed Product Pursuant to DASR 21.A.101

Notes:
1.    Changed products that are substantially changed do not follow this flowchart. Refer to DASR 21.A.19
2.    Process and propose each applicable standard individually. If standards are linked together, then they should be assessed together.
 

3.2        Step 1. Identify the proposed changes to an aeronautical product.

Identify the type design being changed (the baseline product).

Identify the proposed change.

Use high‐level descriptors.

3.2.1    Identify the type design being changed (the baseline product).

Prior to describing the proposed change(s), it is important to clearly identify the specific type design configuration being changed.

Note: For additional guidance on the baseline product, see paragraph 5.3 of this GM.

3.2.2    Identify the proposed change.

3.2.2.1    The purpose of this process step is to identify and describe the change to the aeronautical product. Changes to a product can include physical design changes and functional changes (e.g. operating envelope or performance changes). An applicant must identify all changes and areas affected by the change, including those where they plan to use previously approved data. The Authority considers all of these changes and areas affected by the change to be part of the entire proposed type design and they are considered as a whole in the classification of whether the proposed change is substantial, significant, or not significant. The change can be a single change or a collection of changes. In addition to the proposed changes, an applicant should consider the cumulative effect of previous relevant changes incorporated since the last time the certification basis was upgraded. An applicant for a change must consider all previous relevant changes and the amendment level of the airworthiness requirements in the certification basis used for these changes.

3.2.2.2    When identifying the proposed changes, an applicant should consider previous relevant changes that create a cumulative effect, as these may influence the decisions regarding the classification of the change later in the process. By ‘previous relevant changes,’ the Authority means changes where effects accumulate, such as successive thrust increases, incremental weight increases, or sectional increases in fuselage length. An applicant must account for any previous relevant changes to the area affected by the proposed change that did not involve an upgrade of the certification basis in the proposed change.

3.2.2.3    Example:

An applicant proposes a 5 per cent weight increase, but a previous 4 per cent and another 3 per cent weight increase were incorporated into this aircraft without upgrading the existing certification basis. In the current proposal for a 5 per cent weight increase, the cumulative effects of the two previous weight increases that did not involve an upgrade of the certification basis will now be accounted for as an approximate 12 per cent increase in weight. Note that the cumulative effects the applicant accounts for are only those incremental increases since the last time the airworthiness requirements in the type‐certification basis applicable to the area affected by the proposed change were upgraded.

3.2.3    Use High‐Level Descriptors.

To identify and describe the proposed changes to any aeronautical product, an applicant should use a high‐level description of the change that characterises the intent of, or the reason for, the change. No complex technical details are necessary at this stage. For example, a proposal to increase the maximum passenger‐carrying capacity may require an addition of a fuselage plug, and as such, a ‘fuselage plug’ becomes one possible high‐level description of this change. Similarly, a thrust increase, a new or complete interior, an avionics system upgrade, or a passenger‐to‐cargo conversion are all high‐level descriptions that characterise typical changes to the aircraft, each driven by a specific goal, objective, or purpose.

3.2.4    Evolutionary Changes

Evolutionary changes that occur during the course of a certification program may require re‐evaluation of the certification basis, and those changes that have influence at the product level may result in re‐classification of the change.

3.3        Step 2. Verify the proposed change is not substantial.

3.3.1    DASR 21.A.19 requires an applicant to apply for a new MTC for a changed product if the change to design, power, thrust, or weight is so extensive that a substantially complete investigation of compliance with the applicable regulations is required. A new MTC could be required for either a single extensive change to a previously type‐certified product or for a changed design derived through the cumulative effect of a series of design changes from a previously type‐certified product.

3.3.2    A ‘substantially complete investigation’ of compliance is required when most of the existing substantiation is not applicable to the changed product. In other words, an applicant may consider the change ‘substantial’ if it is so extensive (making the product sufficiently different from its predecessor) that the design models, methodologies, and approaches used to demonstrate a previous compliance finding could not be used in a similarity argument. The Authority considers a change ‘substantial’ when these approaches, models, or methodologies of how compliance was shown are not valid for the changed product.

3.3.3    A substantial change requires an application for a new MTC. See DASR 21.A.17A, DASR 21.A.18 and DASR 21.A.19. If the change is not substantial, proceed to step 3. If it is not initially clear that a new MTC is required, appendix A of this GM provides references to examples of substantial changes to aid in this classification. 

3.4        Step 3. Will the applicant use the latest standards?

3.4.1    An applicant can use the latest airworthiness requirements for their proposed change and the area affected by the change. If they use the latest airworthiness requirements, they will have met the intent of DASR 21.A.101 and no further classification (significant or not significant) and justification is needed. Even though an applicant elects to use the latest airworthiness requirements, the applicant will still be able to apply DASR 21.A.101 for future similar changes, and use the exceptions under DASR 21.A.101(b). However, the decision to comply with the latest airworthiness requirements sets a new basis for all future related changes to the same affected area for that amended MTC.

If using the latest airworthiness requirements, an applicant should proceed to Step 6 (in paragraph 3.9 of this GM)

If not using the latest airworthiness requirements, an applicant should proceed to Step 4 below.

3.5        Step 4. Arrange changes into related and unrelated groups.

3.5.1    An applicant should now determine whether any of the changes identified in Step 1 are related to each other. Related changes are those that cannot exist without another, are co‐dependent, or a prerequisite of another. For example, a need to carry more passengers could require the addition of a fuselage plug, which will result in a weight increase, and may necessitate a thrust increase. Thus, the fuselage plug, weight increase, and thrust increase are all related, high‐level changes needed to achieve the goal of carrying more passengers. A decision to upgrade the flight deck to more modern avionics at the same time as these other changes may be considered unrelated, as the avionics upgrade is not necessarily needed to carry more passengers (it has a separate purpose, likely just modernisation). The proposed avionics upgrade would then be considered an unrelated (or a stand‐alone) change. However, the simultaneous introduction of a new cabin interior is considered related since occupant safety considerations are impacted by a cabin length change. Even if a new cabin interior is not included in the product‐level change, the functional effect of the fuselage plug has implications on occupant safety (e.g. the dynamic environment in an emergency landing, emergency evacuation, etc.), and thus the cabin interior becomes an affected area. Figure 3‐2 below illustrates the grouping of related and unrelated changes using the example of increasing the maximum number of passengers.
Note: An applicant who plans changes in sequence over time should refer to the discussion on ‘sequential design changes’ in paragraph 5.13 of this GM.

Figure 3‐2. Related and Unrelated Changes for Example of Increasing the Maximum Number of Passengers

3.5.2    Once the change(s) is (are) organised into groupings of those that are related and those that are unrelated (or stand‐alone), an applicant should proceed to Step 5 below.

3.6        Step 5. Is each group of related changes or each unrelated (stand‐alone) change a significant change?

3.6.1    The applicant is responsible for proposing the classification of groups of related changes or unrelated changes as ‘significant’ or ‘not significant’. Significant changes are product‐level changes that could result from an accumulation of changes, or occur through a single significant change that makes the changed product distinct from its baseline product. The grouping of related and unrelated changes is particularly relevant to the Authority’s significant Yes/No decision (DASR 21.A.101(b)(1)) described in Step 1 of Figure 3‐1. The Authority evaluates each group of related changes and each unrelated (stand‐alone) change on its own merit for significance. Thus, there may be as many evaluations for significance as there are groupings of related and unrelated changes. Step 1 of Figure 3‐1 explains the accumulation of changes that an applicant must consider. Additionally, DASR 21.A.101(b)(1) defines a change as ‘significant’ when at least one of the three automatic criteria applies:

3.6.1.1    Changes where the general configuration is not retained (significant change to general configuration).

                A change to the general configuration at the product level is one that distinguishes the resulting product from other product models, for example,                  performance or interchangeability of major components. Typically, for these changes, an applicant will designate a new product model, although                  this is not required.

3.6.1.2    Changes where the principles of construction are not retained (significant change to principles of construction).
A change at the product level to the materials and/or construction methods that affects the overall product’s operating characteristics or inherent strength and would require extensive reinvestigation to demonstrate compliance is one where the principles of construction are not retained.

3.6.1.3    Product‐level changes that invalidate the assumptions used for certification of the baseline product. Examples include:

change of an aircraft from an unpressurised to pressurised fuselage,

change of operation of a fixed‐wing aircraft from land‐based to water‐based, and

operating envelope expansions that are outside the approved design parameters and capabilities.

3.6.2    The above criteria are used to determine whether each change grouping and each stand‐alone change is significant. These three criteria are assessed at the product level. In applying the automatic criteria an applicant should focus on the change and how it impacts the existing product (including its performance, operating envelope, etc.). A change cannot be classified or reclassified as a significant change on the basis of the importance of a later amendment.

3.6.3    Appendix A of this GM includes references to tables of typical changes (examples) for various product classes (e.g. small aeroplanes, transport aeroplanes, rotorcraft, engines, and propellers) that would meet the criteria for a significant design change. These references also include tables of typical design changes that would not be classified as significant. The tables can be used in one of two ways: 

3.6.3.1 To identify the classification of a proposed design change listed in the table, or 

3.6.3.2 In conjunction with the three automatic criteria, to help classify a proposed design change not listed in the table by comparison to determinations made for changes with similar type and magnitude. 

In any case, the final classification should be accepted by the Authority.
 

3.6.4    In many cases, a significant change may involve more than one of these criteria and will be obvious and distinct from other product improvements or production changes. There could be cases where a change to a single area, system, component, or appliance may not result in a product‐level change. There could also be other cases where the change to a single system or component might result in a significant change due to its effect on the product overall. Examples may include the addition of winglets or leading‐edge slats, or a change to primary flight controls of a fly‐by‐wire system.

3.6.5    If an unrelated (stand‐alone) change or a grouping of related changes is classified as:

3.6.5.1    Significant (DASR 21.A.101(a)):

You must comply with the latest airworthiness standards for certification of the change and areas affected by change, unless you justify use of one of the exceptions provided in DASR 21.A.101(b)(2) or (3) to show compliance with earlier amendment(s). The final certification basis may consist of a combination of the requirements recorded in the certification basis ranging from the original aircraft certification basis to the most current regulatory amendments.

3.6.5.2    Not Significant (DASR 21.A.101(b)(1)):

You may comply with the existing certification basis unless the standards in the proposed certification basis are deemed inadequate. In cases where the existing certification basis is inadequate or no regulatory standards exist, later requirements and/or special conditions will be required. See paragraph 3.11 of this GM for a detailed discussion.

3.6.6    A new model designation to a changed product is not necessarily indicative that the change is significant under DASR 21.A.101. Conversely, retaining the existing model designation does not mean that the change is not significant. Significance is determined by the magnitude of the change.

3.6.7    The Authority determines the final classification of whether a change is significant or not significant. To assist an applicant in its assessment, the Authority may predetermine the classification of several typical changes that an applicant could use for reference. Such examples are referred to in appendix A of this GM.

3.6.8    At this point, the determination of significant or not significant for each of the groupings of related changes and each stand‐alone change is completed. For significant changes, an applicant that proposes to comply with an earlier amendment of a requirement should use the procedure outlined in paragraph 3.7 below. For changes identified as not significant, see paragraph 3.8 below.

3.7        Proposing an amendment level for a significant change.

3.7.1    Without prejudice to the exceptions provided for in DASR 21.A.101(b), if the classification of a group of related changes or a stand‐alone unrelated change is significant, all areas, systems, components, parts, or appliances affected by the change must comply with the airworthiness requirements at the amendment level in effect on the date of application for the change, unless the applicant elects to comply with airworthiness requirements that have become effective after that date (see DASR 21.A.101(a)).

3.7.2    In certain cases, an applicant will be required by the Authority to comply with airworthiness requirements that have become effective after the date of application (see DASR 21.A.101(a)):

3.7.2.1    If an applicant elects to comply with a specific airworthiness requirement or a group of airworthiness requirements at an amendment which has become effective after the date of application, the applicant must comply with any other airworthiness requirement that the Authority finds is directly related (see DASR 21.A.101(f)).

3.7.2.2    In a case where the change has not been approved, or it is clear that it will not be approved under the time limit established, the applicant will be required to comply with an upgraded certification basis established according to DASR 21.A.17A and 21.A.18 from the airworthiness requirements that have become effective since the date of the initial application.

3.7.3    Applicants can justify the use of one of the exceptions in DASR 21.A.101(b)(2) or (3) to comply with an earlier amendment, but not with an amendment introduced earlier than the existing certification basis. See paragraphs 3.9 and 3.10 of this GM. Applicants who elect to comply with a specific airworthiness requirement or group of airworthiness requirements at an earlier amendment will be required to comply with any other airworthiness requirements that the Authority finds are directly related.

3.7.4    The final certification basis may combine the latest, earlier (intermediate), and existing amendment levels of requirements, but cannot contain airworthiness requirement spreceding the existing certification basis.

3.8        Proposing an amendment level for a not significant change.

3.8.1    When the Authority classifies the change as not significant, the DASR 21.A.101(b) rule allows compliance with earlier amendments, but not prior to the existing certification basis. Within this limit, the applicant may propose an amendment level for each airworthiness requirement for the affected area. However, each applicant should be aware that the Authority will review their proposals for the certification basis to ensure that the certification basis is adequate for the proposed change under Step 8. (See paragraph 3.11 of this GM.)

3.8.2    Even for a not significant change, an applicant may elect to comply with airworthiness requirements which became applicable after the date of application. Applicants may propose to comply with a specific airworthiness requirement or a group of airworthiness requirements at a certain amendment of their choice. In such a case, any other airworthiness requirements of that amendment that are directly related should be included in the certification basis for the change.

3.9        Step 6. Prepare the proposed certification basis list.

As part of preparing the proposed certification basis list, an applicant must identify any areas, systems, parts or appliances of the product that are affected by the change and the corresponding airworthiness requirements associated with these areas. For each group, the applicant must assess the physical and/or functional effects of the change on any areas, systems, parts or appliances of the product. The characteristics affected by the change are not only physical changes, but also functional changes brought about by the physical changes. Examples of physical aspects are structures, systems, parts and appliances, including software in combination with the affected hardware. Examples of functional characteristics are performance, handling qualities, aeroelastic characteristics, and emergency egress. The intent is to encompass all aspects where there is a need for re‐evaluation, that is, where the substantiation presented for the product being changed should be updated or rewritten.

3.9.1    An area affected by the change is any area, system, component, part, or appliance of the aeronautical product that is physically and/or functionally changed.

3.9.2    Figure 3‐3 of this GM illustrates concepts of physical and functional changes of an affected area. For each change, it is important for the applicant to properly assess the effects of such change on any areas, systems, parts or appliances of the product because areas that have not been physically changed may still be considered part of the affected area. If a new compliance finding is required, regardless of its amendment level, it is an affected area.

Figure 3‐3. Affected Areas versus Not Affected Areas

3.9.3    An area not affected by a change can remain at the existing certification basis, provided that the applicant presents to the Authority an acceptable justification that the area is not affected.

3.9.4    For sample questions to assist in determining affected areas, see below. If the answer to any of these questions is yes, then the area is considered to be affected.

Is the area changed from the identified baseline product?

Is the area impacted by a significant product‐level change?

Is there a functional effect on the unchanged area by a change to the system or system function that it is a part of?

Does the unchanged area need to comply with a system or product‐level certification specification that is part of the change?

Are the product‐level characteristics affected by the change?

Is the existing compliance for the area invalidated?

3.9.5    Consider the following aspects of a change:

3.9.5.1    Physical aspects.

The physical aspects include direct changes to structures, systems, equipment, components, and appliances, and may include software/airborne electronic hardware changes and the resulting effects on systems functions.

3.9.5.2    Performance/functional characteristics.

The less obvious aspect of the word ‘areas’ covers general characteristics of the type‐certified product, such as performance features, handling qualities, emergency egress, structural integrity (including load carrying), aeroelastic characteristics, or crashworthiness. A product‐level change may affect these characteristics. For example, adding a fuselage plug could affect performance and handling qualities, and thus the airworthiness requirements associated with these aspects would be considered to be part of the affected area. Another example is the addition of a fuel tank and a new fuel conditioning unit. This change affects the fuel transfer and fuel quantity indication system, resulting in the aircraft’s unchanged fuel tanks being affected. Thus, the entire fuel system (changed and unchanged areas) may become part of the affected area due to the change to functional characteristics. Another example is changing turbine engine ratings and operating limitations, affecting the engine rotors’ life limits.

3.9.6    All areas affected by the proposed change must comply with the latest airworthiness requirements, unless the applicant shows that demonstrating compliance with the latest amendment of a requirement would not contribute materially to the level of safety or would be impractical. Step 7 below provides further explanation.

3.9.7    The applicant should document the change and the area affected by the change using high‐level descriptors along with the applicable airworthiness requirements and their proposed associated amendment levels. The applicant proposes this change to the certification basis that the Authority will consider for documentation in the type certificate data sheet (TCDS) or MSTC, if they are different from that recorded for the baseline product in the TCDS.

3.10      Step 7. Do the latest standards contribute materially to the level of safety and are they practical?

Pursuant to DASR 21.A.101(a), compliance with the latest airworthiness requirements is required. However, exceptions may be allowed pursuant to DASR 21.A.101(b)(3). The applicant must provide justification to support the rationale for the application of earlier amendments for areas affected by a significant change in order to document that compliance with later standards in these areas would not contribute materially to the level of safety or would be impractical. Such a justification should address all the aspects of the area, system, part or appliance affected by the significant change. See paragraphs 3.10.1 and 3.10.1.4 of this GM.

3.10.1    Do the latest standards contribute materially to the level of safety?

Applicants could consider compliance with the latest standards to ‘not contribute materially to the level of safety’ if the existing type design and/or relevant experience demonstrates a level of safety comparable to that provided by the latest standards. In cases where design features provide a level of safety greater than the existing certification basis, applicants may use acceptable data, such as service experience, to establish the effectiveness of those design features in mitigating the specific hazards by a later amendment. Applicants must provide sufficient justification to allow the Authority to make this determination. An acceptable means of compliance is described in appendix E of this GM. Justification is sufficient when it provides a summary of the evaluation that supports the determination using an agreed evaluation method, such as that in appendix E of this GM. This exception could be applicable in the situations described in the paragraphs below.

Note: Compliance with later standards is not required where the amendment is of an administrative nature and made only to correct inconsequential errors or omissions, consolidate text, or to clarify an existing requirement.

3.10.1.1    Improved design features.

Design features that exceed the existing certification basis standards, but do not meet the latest airworthiness requirements, can be used as a basis for granting an exception under DASR 21.A.101(b)(3) since complying with the latest amendment of the airworthiness requirements would not contribute materially to the level of safety of the product. If the Authority accepts these design features as justification for an exception, the applicant must incorporate them in the amended type design configuration and record them, where necessary, in the certification basis. The description of the design feature would be provided in the TCDS or MSTC at a level that allows the design feature to be maintained, but does not contain proprietary information. For example, an applicant proposes to install winglets on a large aeroplane, and part of the design involves adding a small number of new wing fuel tank fasteners. Assuming that the latest applicable amendment of the certification requirement requires structural lightning protection, the applicant could propose an exception from these latest structural lightning protection requirements because the design change uses new wing fuel tank fasteners with cap seals installed. The cap seal is a design feature that exceeds the requirement of the previous amendment level, but does not meet the latest amendment. If the applicant can successfully substantiate that compliance with the latest amendment would not materially increase the level of safety of the changed product, then this design feature can be accepted as an exception to compliance with the latest amendment.

3.10.1.2    Consistency of design.

This provision gives the opportunity to consider the consistency of design. For example, when a small fuselage plug is added, additional seats and overhead bins are likely to be installed, and the lower cargo hold extended. These components may be identical to the existing components. The level of safety may not materially increase by applying the latest airworthiness requirements in the area of the fuselage plug. Compliance of the new areas with the existing certification basis may be acceptable.

3.10.1.3    Service experience.

3.10.1.3.1    Relevant service experience, such as experience based on fleet performance or utilisation over time (relevant flight hours or cycles), is one way of showing that the level of safety will not materially increase by applying the latest amendment, so the use of earlier amendments of requirements could be appropriate.

3.10.1.3.2    When establishing the highest practicable level of safety for a changed product, the Authority has determined that it is appropriate to assess the service history of a product, as well as the later airworthiness standards. It makes little sense to mandate changes to well‐understood designs, whose service experience has been acceptable, merely to comply with new standards. The clear exception to this premise is if the new standards were issued to address a deficiency in the design in question, or if the service experience is not applicable to the new standards.

3.10.1.3.3    There may be cases where relevant data may not be sufficient or not available at all because of the low utilisation and the insufficient amount and type of data available. In such cases, other service history information may provide sufficient data to justify the use of earlier amendments of requirements, such as: warranty, repair, and parts usage data; accident, incident, and service difficulty reports; service bulletins; airworthiness directives; or other pertinent and sufficient data collected by the manufacturers, authorities, or other entities.

3.10.1.3.4    The Authority will determine whether the proposed service experience levels necessary to demonstrate the appropriate level of safety as they relate to the proposed design change are acceptable.

3.10.1.4    Secondary changes.

3.10.1.4.1    The change proposed by the applicant can consist of physical and/or functional changes to the product. See Figure 3‐4 below. There may be aspects of the existing type design of the product that the applicant may not be proposing to change directly, but that are affected by the overall change. For example, changing an airframe’s structure, such as adding a cargo door in one location, may affect the frame or floor loading in another area. Further, upgrading engines with new performance capabilities could require additional demonstration of compliance for minimum control speeds and aeroplane performance requirements.

Figure 3‐4. Change‐Affected Areas with Secondary Changes

3.10.1.4.2    For each change, it is important that the effects of the change on other systems, components, equipment, or appliances of the product are properly identified and assessed. The intent is to encompass all aspects where there is a need for re‐evaluation, that is, where the substantiation presented for the product being changed should be reviewed, updated, or rewritten.

3.10.1.4.3    In assessing the areas affected by the change, it may be helpful to identify secondary changes. A secondary change is a change to physical and/or functional aspects that is part of, but consequential to, a significant physical change, whose only purpose is to restore, and not add or increase, existing functionality or capacity. The term ‘consequential’ is intended to refer to:

a change that would not have been made by itself; it achieves no purpose on its own;

a change that has no effect on the existing functionality or capacity of areas, systems, structures, components, parts, or appliances affected by the change; or

a change that would not create the need for: (1) new limitations or would affect existing limitations; (2) a new aircraft flight manual (AFM) or instructions for continued airworthiness (ICA) or a change to the AFM or ICA; or (3) special conditions, equivalent safety findings, or Exceptions.

3.10.1.4.4    A secondary change is not required to comply with the latest airworthiness requirements because it is considered to be ‘not contributing materially to the level of safety’ and, therefore, eligible for an exception under DASR 21.A.101. Determining whether a change meets the description for a secondary change, and is thus eligible for an exception, should be straightforward. Hence, the substantiation or justification need only be minimal. If this determination is not straightforward, then the proposed change is not a secondary change.

3.10.1.4.5    In some cases, a secondary area of change that restores functionality may in fact contribute materially to the level of safety by meeting a later amendment. If this is the case, it is not considered a secondary change.

3.10.2    Are the latest standards practical?

The intent of DASR 21.A.101 is to enhance safety by applying the latest airworthiness requirements to the greatest extent practicable. The concepts of contributing materially and practicality are linked. If compliance with the latest airworthiness requirements does contribute materially to the level of safety, then the applicant may assess the incremental costs to see whether they are commensurate with the increase in safety. The additional resource requirements could include those arising from changes required for compliance and the effort required to demonstrate compliance, but excluding resource expenditures for prior product changes. The cost of changing compliance documentation and/or drawings is not an acceptable reason for an exception.

3.10.2.1    Applicants should support their position that compliance is impractical with substantiating data and analyses. While evaluating that position and the substantiating data regarding impracticality, the Authority may consider other factors (e.g. the costs and safety benefits for a comparable new design).

3.10.2.2    A review of large aeroplane projects showed that, in certain cases where the Authority allowed an earlier amendment of applicable airworthiness requirements, the applicants made changes that nearly complied with the latest amendments. In these cases, the applicants successfully demonstrated that full compliance would require a substantial increase in the outlay or expenditure of resources with a very small increase in the level of safety. These design features can be used as a basis for granting an exception under DASR 21.A.101(b)(3) on the basis of ‘impracticality.’

3.10.2.3   Appendix E of this GM provides additional guidance and examples for evaluating the impracticality of applying the latest airworthiness codes or standards to a changed product for which compliance with the latest airworthiness codes or standards would contribute materially to the level of safety of the product.

3.10.2.3.1    The exception of impracticality is a qualitative and quantitative cost–safety benefit assessment for which it is difficult to specify clear criteria. Experience to date with applicants has shown that a justification of impracticality is more feasible when both the applicant and the Authority agree during a discussion at an early stage that the effort (in terms of cost, changes to manufacturing, etc.) required to comply would not be commensurate with a small incremental safety gain. This would be clear even without the need to perform any detailed cost–safety benefit analysis (although an applicant could always use cost analysis to support an appropriate amendment level). However, there should be enough detail in the applicant’s rationale to justify the exception.

Note: An applicant should not base an exception due to impracticality on the size of the applicant’s company or their financial resources. The applicant must evaluate the costs to comply with a later amendment against the safety benefit of complying with the later amendment.

3.10.2.3.2    For example, a complex redesign of an area of the baseline aircraft may be required to comply with a new requirement, and that redesign may affect the commonality of the changed product with respect to the design and manufacturing processes of the existing family of models. Relevant service experience of the existing fleet of the baseline aircraft family would be required to show that there has not been a history of problems associated with the hazard that the new amendment in question was meant to address. In this way, the incremental cost/impact to the applicant is onerous, and the incremental safety benefit realised by complying with the later amendment would be minimal. This would be justified by demonstrated acceptable service experience in relation to the hazard that the new airworthiness requirement addresses.

3.11      Step 8. Ensure the proposed certification basis is adequate.

The Authority considers a proposed certification basis for any change (whether it is significant or not significant) to be adequate when:

the airworthiness requirements provide an appropriate level of safety for the intended change, and

the change and the areas affected by the change do not result in unsafe design features or characteristics for the intended use.

3.11.1    For a change that contains new design features that are novel and unusual for which there are no applicable airworthiness requirements at a later amendment level, the Authority will designate special conditions pursuant to DASR 21.A.16B. The Authority will impose later airworthiness requirements that contain adequate or appropriate safety standards for this feature, if they exist, in lieu of special conditions. An example is adding a flight‐critical system, such as an electronic air data display on a large aeroplane whose existing certification basis does not cover protection against lightning and high‐intensity radiated fields (HIRF). In this case, the Authority will require compliance with the airworthiness requirements for lightning and HIRF protection, even though the Authority determined that the change is not significant.

3.11.2    For new design features or characteristics that may pose a potential unsafe condition for which there are no later applicable airworthiness requirements, new special conditions may be required.

3.11.3    In cases where inadequate or no standards exist for the change in the existing certification basis, but adequate standards exist in a later amendment of the applicable airworthiness requirements, the later amendment will be made part of the certification basis to ensure the adequacy of the certification basis.

3.11.4    The Authority determines the final certification basis for a product change. This may consist of a combination of those standards ranging from the existing certification basis of the baseline product to the latest amendments and special conditions.

4.          (Reserved)

5.          Other Considerations

5.1        Design‐related requirements from other aviation domains.

Some implementing rules in other aviation domains (air operations, ATM/ANS) impose airworthiness standards that are not required for the issue of a MTC or MSTC. If not already included in the certification basis, any such applicable airworthiness standard may be added to the type certification basis by mutual agreement between the applicant and the Authority. The benefit of adding these airworthiness standards to the type certification basis is to increase awareness of these standards, imposed by other implementing rules, during design certification and future modifications to the aircraft. The use of exceptions under DASR 21.A.101(b) is not intended to alleviate or preclude compliance with operating regulations.

5.2        (Reserved)

5.3        Baseline product.

A baseline product consists of one unique type design configuration, an aeronautical product with a specific, defined, approved configuration and certification basis that the applicant proposes to change. As mentioned in paragraph 3.2.1 of this GM, it is important to clearly identify the type design configuration to be changed. The Authority does not require an applicant to assign a new model name for a changed product. Therefore, there are vastly different changed products with the same aircraft model name, and there are changed products with minimal differences that have different model names. The identification of the baseline product, for the purposes of DASR 21.A.101, is as defined below.

The baseline product is an approved type design that exists at the date of application and is representative of:

a single certified build configuration, or

multiple approvals over time (including MSTC(s) or service bulletins) and may be representative of more than one product serial number.

Note: The type design configuration, for this purpose, could also be based on a proposed future configuration that is expected to be approved at a later date but prior to the proposed changed product.

5.4        (Reserved)

5.5        Special conditions, DASR 21.A.101(d).

DASR 21.A.101(d) allows for the application of special conditions, or for changes to existing special conditions, to address the changed designs where neither the proposed certification basis nor any later amendments of requirements in the certification basis provide adequate standards for an area, system, part or appliance related to the change. The objective is to achieve a level of safety consistent with that provided for other areas, systems, parts or appliances affected by the change by the other requirements in the proposed certification basis. The application of special conditions to a design change is not, in itself, a reason to classify it as either a substantial change or a significant change. Whether the change is significant, with earlier amendments of airworthiness requirements allowed through exceptions, or not significant, the level of safety intended by the special conditions must be consistent with the agreed certification basis.

5.6        (Reserved)

5.7        (Reserved)

5.8        (Reserved)

5.9        Documentation.

5.9.1    Documenting the proposal.

In order to efficiently determine and agree upon a certification basis with the Authority, the following information is useful to understand the applicant’s position:

The current certification basis of the product being changed, including the amendment level.

The amendment level of all the applicable airworthiness requirements at the date of application.

The proposed certification basis, including the amendment levels.

Description of the affected area.

Applicants who propose a certification basis that includes amendment levels earlier than what was in effect at the date of application should include the exception as outlined in DASR 21.A.101(b) and their justification if needed.

5.9.2    (Reserved)

5.9.3    Documenting the certification basis.

5.9.3.1    The Authority will amend the certification basis for all changes that result in a revision to the product’s certification basis on the amended TCDS or MSTC.

5.10      Incorporation of MSTCs into the Type Design.

The incorporation of MSTCs into the product type design may generate an additional major change when that change is needed to account for incompatibility between several MSTCs that were initially not intended to be applied concurrently.

5.10.1    If the incorporation of the MSTC(s) does not generate an additional major change, the incorporation is not evaluated pursuant to DASR 21.A.101. The existing certification basis should be updated to include the later amendments of the MSTC(s) being incorporated.

5.10.2    If the incorporation of the MSTC(s) generates an additional major change, the change must be evaluated pursuant to DASR 21.A.101, and the existing certification basis should be updated to include the amendments resulting from the application of DASR 21.A.101.

5.11      Removing changes.

Approved changes may be removed after incorporation in an aeronautical product. These changes will most commonly occur via an MSTC or a service bulletin kit.

5.11.1    The applicant should identify a product change that they intend at its inception to be removable as such, and should develop instructions for its removal during the initial certification. The Authority will document the certification basis for both the installed and removed configuration separately on the TCDS or MSTC.

5.11.2    If specific removal instructions and a certification basis corresponding to the removed condition are not established at the time of the initial product change certification, the removal of changes or portions of those changes may constitute a significant change to type design. A separate MSTC or an amended MTC may be required to remove the modifications and the resulting certification basis established for the changed product.

5.12    The certification basis is part of the change.

A new change may be installed in a product during its production or via a service bulletin or MSTC. In terms of DASR 21.A.101, each of the approved changes has its own basis of certification. If an applicant chooses to remove an approved installation (e.g. an interior installation, avionics equipment) and install a new installation, a new certification basis may be required for the new installation, depending on whether the change associated with the new installation is considered significant compared to the baseline configuration that the applicant chooses. If the new installation is a not significant change, the unmodified product’s certification basis may be used (not the previous installation certification basis), provided the certification basis is adequate.

5.13    Sequential changes — cumulative effects.

5.13.1    Any applicant who intends to accomplish a product change by incorporating several changes in a sequential manner should identify this to the Authority up front when the first application is made. In addition, the cumulative effects arising from the initial change, and from all of the follow‐on changes, should be included as part of the description of the change in the initial proposal. The classification of the intended product change will not be evaluated solely on the basis of the first application, but rather on the basis of all the required changes needed to accomplish the intended product change. If the Authority determines that the current application is a part of a sequence of related changes, then the Authority will re‐evaluate the determination of significance and the resulting certification basis as a group of related changes.

5.13.2    Example: Cumulative effects — advancing the certification basis.

The type certificate for aeroplane model X lists three models, namely X‐300, X‐200, and X‐100. The X‐300 is derived from the X‐200, which is derived from the original X‐ 100 model. An applicant proposes a change to the X‐300 aeroplane model. During the review of the X‐300 certification basis and the airworthiness requirements affected by the proposed change, it was identified that one requirement, damage tolerance, remained at the same amendment level as the X‐100 original certification basis (exception granted on the X‐200). Since the amendment level for this particular requirement was not changed for the two subsequent aeroplane models (X‐200 and X‐300), the applicant must now examine the cumulative effects of these two previous changes that are related to the proposed change and the damage tolerance requirements to determine whether the amendment level needs to advance.

Appendix A to GM 21.A.101 - Classification of design changesAppendix A to GM 21.A.101 - Classification of design changes

Appendix B to GM 21.A.101 - Application charts for changed product ruleAppendix B to GM 21.A.101 - Application charts for changed product rule

Appendix C to GM 21.A.101 - A method to determine the changed and affected areasAppendix C to GM 21.A.101 - A method to determine the changed and affected areas

Appendix D to GM 21.A.101 - Other guidance for affected areasAppendix D to GM 21.A.101 - Other guidance for affected areas

Appendix E to GM 21.A.101 Procedure for evaluating material contribution to safety or impracticality of applying latest airworthiness codes to a changed product Appendix E to GM 21.A.101 Procedure for evaluating material contribution to safety or impracticality of applying latest airworthiness codes to a changed product   

Appendix F to GM 21.A.101 - The use of service experience in the exception processAppendix F to GM 21.A.101 - The use of service experience in the exception process

Appendix G to GM 21.A.101 - Changed product rule (CPR) decision recordAppendix G to GM 21.A.101 - Changed product rule (CPR) decision record

Appendix H to GM 21.A.101 - Examples of documenting the proposed certification basis listAppendix H to GM 21.A.101 - Examples of documenting the proposed certification basis list

Appendix I to GM 21.A.101 - Related documentsAppendix I to GM 21.A.101 - Related documents

Appendix J to GM 21.A.101 - Definitions and terminologyAppendix J to GM 21.A.101 - Definitions and terminology

GM 21.A.107 - Instructions for Continuing Airworthiness (AUS)

Instructions for Continuing Airworthiness (ICA) details the methods, inspections, processes, and procedures necessary for the air operator to keep aircraft and / or engine, propeller, parts and appliances airworthy during its intended life.

The contents of ICA can be divided into two categories:

an approved airworthiness limitations (AwL) section as defined by the applicable airworthiness codes during the certification process, which forms part of the type design / type‐certificate (DASR 21.A.31(a)(3) and DASR 21.A.41):

any limitations determined through the certification of the product, and instructions on how to determine that these limits have been exceeded.

any inspection, servicing or maintenance actions determined to be necessary by the certification process.

sections that do not contain approved data from the certification process and are not considered as part of type design/type‐certificate:

any inspection or troubleshooting actions determined to be necessary to establish the nature of faults and the necessary remedial actions.

sufficient general information on the operation of the product to enable an understanding of the instructions in paragraphs (a)(i), (a)(ii), and (b)(i) above.

GM 21.A.112B - Demonstration of capability for Military supplemental type-certificate cases

See also DASR AMC 21.A.14(b) for the details of the alternative procedures.

The following examples of major changes to type design (see DASR 21.A.91) are classified in two groups. Group 1 contains cases where a design organisation approved under DASR 21 Section A Subpart J ('Subpart J MDOA') will be required, and Group 2 cases where the alternative procedure may be accepted. They are typical examples but each MSTC case is to be addressed on its merits and there would be exceptions in practice. This classification is valid for new MSTCs, not for evolution of MSTCs, and may depend upon the nature of the MSTC (complete design or installation).

PRODUCT	DISCIPLINE	KIND OF MSTC	GROUP
SMALL AIRCRAFT (products where Subpart J MDOA is required for MTC)
NOTES: * MSTC which leads to reassess the loads on large parts of primary structure will be in Group 1. * 2/1 means that an assessment of consequences in terms of handling qualities, performance or complexity of demonstration of compliance may lead to classification in Group 1.
	Aircraft
		Conversion to tail wheel configuration	1
		Auxiliary fuel tank installations	2/1
		Glass fibre wing tips	2/1
		Fairings: nacelle, landing gear	2
		Gap seals: aileron, flap, empennage, doors	2
		Vortex generators	2/1
		Spoiler installation	1
		Increase in Maximum Take-off Weight (MTOW)	1
	Structures
		Stretcher installation	2
		Change to seating configuration	2
		Windshield replacement (heated, single piece, etc)	2
		Light weight floor panels	2
		Ski installations	2/1
	Propulsion
		Engine model change	1
		Fixed pitch propeller installation	2
		Constant speed propeller installation	2/1
		Installation of exhaust silencer	2
		Installation of Graphic engine monitor	2
		Installation of fuel flow meter	2
		Accessory replacement (alternator, magnetos, etc.)	2
		Inlet modifications: oil cooler; induction air	2
	Equipment
		Avionics upgrades (Electronic Flight Instrument System (EFIS), Global Posistioning System (GPS), etc)	2/1
		Engine instrument replacements	2
		Carburetor ice detection system	2
		Autopilot system installation	1
		Wing tip landing light; recognition lights	2
		Weather (WX) radar installation	2
		Aeromedical system installations	2
		De- and anti-ice system installations	1
		Emergency power supply installations	2
LARGE AIRCRAFT
	Cabin safety
NOTE: Basically all changes related to cabin configuration will be in Group 2.		Cabin layout (installation of seats (16G), galleys, single class or business / economy class, etc)	2
		Floor path marking	2
		Crew rest compartment	1
		Change of cargo compartment classification (from class D to class C)	1
	Structure
NOTE: MSTC which leads to reassess the loads on large parts of primary structure will be in Group 1.		Cargo door	1
		Change from Passenger to Freighter configuration	1
	Avionics
NOTES: For large aircraft products, the existence of AUSMTSO is not taken into account for the classification ; Impact on aircraft performance, and influence of aircraft performance are criteria to assess the classification ; Subjective assessment of human factors is considered for determination of classification.		Cockpit Voice Recorder (CVR)	2
		Very High Frequency (VHF)	2
		Navigation (NAV) - (Automatic Direction Finder (ADF), VH Omnidirectional Range (VOR), GPS, Basic Area Navigation (B-RNAV)	2
		Autopilot, Head-up Display (HUD), EFIS, Flight Management System (FMS)	1
		Digital Flight Data Recorder (DFDR)	2/1
		Meteo radar	2
		Instrument Landing System (ILS) Cat 3	1
		Reduced Vertical Separation Minima (RVSM)	1
		Traffic Collission Avoidance System (TCAS), Enhanced Ground Proximity Warning System (EGPWS)	1
		Ground Proximity Warning System (GPWS)	2
	Powerplant
		Auxiliary fuel tanks	1
		Thrust Reverser system	1
		Hushkit	1
		Fire detection	1
		Fuel gauging	1
		Change of Engine or Propeller	1
HELICOPTERS
	All disciplines
NOTE: 2/1 means that an assessment of consequences in terms of handling qualities and performance may lead to classification in Group 1.		Main rotor or tail rotor blades replacement	1
		Autopilot	1
		Engine type change	1
		GPS installation	2
		Jettisonable overhead raft installation	2
		Utility basket installation	2/1
		Nose or side mount camera installation	2/1
		Passenger access step installation	2/1
		Protection net & handle installation (parachuting)	2
		Very Important Person (VIP) cabin layout	2
		Navigation system installation	2
		Fuel boost pump automatic switch-on installation	2
		Decrease of maximum seating capacity	2
		Agricultural spray kit installation	2/1
		Long exhaust pipe installation	2
		Flotation gear installation	2/1
		Wipers installation	2
		Engine oil filter installation	2
		Skid gear covering installation	2/1
		Gutter installation (top pilot door)	2
		Cable cutter installation	2
		Auxiliary fuel tank fixed parts installation	2
		Cabin doors windows replacement	2
		Radio-altimeter aural warning installation	2
		Stand-by horizon autonomous power supply	2
		Fire attack system	2/1
		Hoisting system installation	2/1
		External loads hook installation	2
		Emergency flotation gear installation	2/1
		Heating/demisting (P2 supply)	2