6.2 This chapter presents the Authority prescribed CCPDR.
6.3 This section discusses the basis for the Authority prescribed CCPDR in terms of the design principles associated with crash protection, the definition of ‘benign’ and ‘challenging’ environments and the broad application of civil and military Authority approved Airworthiness Codes, to provide context for the application of the CCPDR.
6.4 A successful crash protection strategy is one that protects occupants from fatalities and serious injury in potentially survivable crashes while limiting capability reductions, implementation costs and additional maintenance overheads. To optimise occupant protection, a systems approach to crash protection is necessary, encompassing the following five key crash protection principles:
Aircraft crash resistance. The ability of the aircraft structure to provide a protective shell for occupants in the event of a survivable crash is a key factor for occupant survival. The structure and equipment should be designed to allow deformation in a controlled, predictable manner so that forces imposed upon the occupants will be tolerable while still maintaining a protective shell. Restraint of concentrated (or high) mass items should prevent parts of the aircraft becoming projectiles within the cabin during a crash creating crushing or blunt trauma hazards (eg engines/transmission/blades coming through the roof, internally mounted items dislodging, and so on).
Occupant retention. Protection should be afforded to occupants by the aircraft’s retention system, which comprises the seat, seat retention and occupant restraint system assembly. The retention system plays a major role in preventing occupant contact injuries associated with body parts flailing into aircraft structures and plays a predominant role in energy absorption (seating design).
Cargo and equipment retention. Restraint systems should be designed to control cargo and ancillary equipment displacements that are hazardous to occupants during a survivable crash.
Post-crash emergency escape provisions. Occupants should retain the ability to rapidly evacuate the aircraft during non-crash ground emergencies, and after survivable crash conditions. The ability to escape is impacted by aircraft deformation, lighting, escape hatches, and so on.
Post-crash injury prevention. The crash protection system should be designed to prevent post-crash environmental hazards that could seriously injure occupants. For hazards which cannot be prevented, the crash protection system should protect occupants from exposure to the hazards. Potential post-crash environmental hazards include fire, toxic fumes and submersion. This principle can be extended to include equipment that can improve post-crash survivability after the crash sequence. Such equipment includes first aid kits, survival kits and emergency locator transmitters.
6.5 These five design principles are addressed by a number of civil and military crash protection design requirements and associated standards. While not considered within the context of the discussion in this Chapter, Aeronautical Life Support Equipment (ALSE) is also a key contributor to crash protection, in particular post-crash injury prevention. Section 5 Chapter 2 of this manual presents the Authority prescribed design requirements for ALSE and should be read in conjunction with this Chapter.
6.6 Civil and military design requirements for aircraft crash protection are structured to accommodate the differences between civil and military operations. In the case of civil operations, the prescribed requirements define a level of crash protection that is appropriate for normal operations in civil aircraft, including consideration of the likelihood of a survivable crash occurring. Military requirements, on the other hand, recognise that due to military operations the likelihood of crashes occurring in broad terms, and therefore the likelihood of a survivable crash occurring, for some military aircraft will be higher than for most civil aircraft. Therefore, the military requirements prescribe more demanding crash protection attributes. The determination of the appropriate suite of crash protection design requirements to apply to a particular Defence aircraft type requires consideration of the circumstances in which a survivable crash is most likely to occur. The application of an appropriate suite of CCPDR to a Defence aircraft type is informed by establishing whether the aircraft will operate in a ‘benign’ or ‘challenging’ environment.
6.7 The following paragraphs discuss the characteristics that would normally be considered as constituting operations in a challenging environment for fixed and rotary wing aircraft. For the purposes of determining which CCPDR apply to a particular Defence aircraft type, if the aircraft operations do not include the characteristics associated with challenging environments, then the operations may be considered ‘benign’.
6.8 Fixed wing. For fixed wing aircraft, the take-off and landing phases of flight carry an inherently higher risk of crashing11. Where military aircraft are routinely conducting tactical take-off / landing, and therefore the likelihood of survivable and non-survivable crashes is increased above the civil norm, this is considered a ‘challenging’ CP environment. While low level tactical flight also increases the likelihood of crashes, the prevalent crashes under these circumstances are expected to be non-survivable and, therefore, are not considered ‘challenging’ from a CP perspective.
6.9 Rotary wing. The rotary wing ‘challenging’ environment includes all helicopter operations where the likelihood of a crash is higher than that which would be expected in normal civil operations. This includes regular low level tactical flight22, extended hover near to the ground, regular ship landings under conditions not experienced during similar civil operations (eg ship landing sites with limited clearance, high sea states), and so on.
6.11 This section discusses the Authority’s approach to establishing CCPDR for benign and challenging environment contexts through the application of crash protection design requirements prescribed in Authority recognised Airworthiness Codes.
6.12 Benign Environment Contemporary Crash Protection Standard. Civil operations are, unsurprisingly, conducted in an operating environment that is consistent with the definition of a benign crash protection environment context as described in paragraphs 6 through 10. Consequently, the design requirements prescribed in Authority recognised civil Airworthiness Codes present an appropriate benchmark against which to assess Defence aircraft crash protection attributes for operations in benign environments. The FAA’s Federal Aviation Regulations (FARs) and EASA’s Certification Specifications (CSs) present airworthiness design requirements for fixed wing aircraft (Parts 23 and 25) and rotary wing aircraft (Parts 27 and 29). These design requirements cover the elements of crash protection such as seat crashworthiness, fire protection, emergency provisions and cargo retention without explicitly identifying the requirements as ‘crash protection’. Although similar in most respects, the FAR and CS crash protection requirements do have some differences. The Authority has determined that the contemporary civil crash protection design requirements for benign operating environments are defined by the most demanding of requirements between the FARs and CSs. Operational regulations can also impose airworthiness design requirements beyond those in the design FARs/CSs (ie Parts 23, 25, 27 and 29). Some of these additional requirements may be relevant to crash protection, for example the requirement for additional safety equipment, improved flammability performance of cabin interiors and so on. Consequently, the Authority has included in the benign contemporary crash protection standard the relevant requirements from FAR Parts 91, 121, 125 and 135 and the applicable Commercial Air Transport (CAT) operational regulations in European Commission Regulation (EU) No 965/2012 Laying down technical requirements and administrative procedures related to air operations pursuant to Regulation (EC) No 216/2008 of the European Parliament and of the Council.
6.13 Summarising, the Authority prescribes the sum of the following as the benign environment contemporary crash protection standard applicable to Defence aircraft:
Airworthiness design requirements provided by the latest amendment of the:
relevant FAR or CS, plus
the alternate relevant FAR or CS requirements that provide an increase to the level of crash protection, plus
Additional design requirements specified in the operational regulations of the:
relevant FAR, CS, EU CAT, plus
the alternate relevant FAR, CS, EU CAT requirements that provide an increase to the level of crash protection.
6.14 Annex A presents the elements of the above standards that constitute the Authority prescribed benign environment contemporary crash protection standard.
6.15 Challenging Environment Contemporary Crash Protection Standard. The US DoD handbooks and standards follow a systems approach to crash protection, and in this respect are superior to the civil standards. Furthermore, they recognise the likely differences in crash scenarios between military and civil aircraft, and specifically cater for the military environment. Therefore, the military standards account for operations that constitute the challenging environment as defined at paragraphs 6 through 10, and present an appropriate benchmark against which to assess Defence aircraft crash protection attributes for operations in challenging environments. MIL-STD-1290A Light Fixed and Rotary-Wing Aircraft Crash Resistance is the prevalent crash protection standard for US military platforms and the Authority has determined that it provides adequate coverage to form the basis of the Authority prescribed challenging environment contemporary crash protection standard for Defence aircraft. Nevertheless, there are a number of crash protection elements, such as head injury criteria (HIC) and femur loads and equipment requirements prescribed in operational FARs, and EU Regulation 965/2012, where the civil design requirements are more onerous than those prescribed in MIL-STD-1290A. Consequently, the Authority has prescribed the challenging environment crash protection standard for Defence aircraft as the requirements prescribed in MIL-STD-1290A supplemented by the relevant requirements from FARs/CSs and civil operational regulations.
6.16 Summarising, the Authority prescribes the sum of the following as a contemporary challenging environment contemporary crash protection standard applicable to Defence aircraft:
design requirements prescribed in the latest amendment of MIL-STD-1290A, plus
HIC and femur load requirements of FAR or CS 2X.562 (whichever is most demanding) using the FAR/CS appropriate for the type and size of aircraft, plus
equipment requirements specified in the most demanding operational regulations of the FARs and EU CAT.
6.17 Annex B presents the elements of the above standards that constitute the Authority prescribed challenging environment contemporary crash protection standard.
6.18 Importantly, the challenging environment contemporary crash protection standard (ie MIL-STD-1290A) has been specifically developed for rotary wing and light fixed wing aircraft operating contexts and associated crash scenarios. Therefore, a straightforward application of the challenging environment standard to large fixed wing aircraft is not appropriate. Consequently, the Authority has determined that the challenging environment contemporary crash protection standard for large fixed wing aircraft is the Annex A benign environment crash protection standard (FAR/CS 25 plus relevant operational regulations) supplemented by applicable Annex B challenging environment crash protection standard (ie MIL-STD-1290A) requirements, where the Annex B requirements are more onerous. Applicable requirements from MIL-STD-1290A will be defined based on the characteristics of the aircraft that are represented in the MIL-STD and for which an improvement in the level of crash protection could be expected through application of the more onerous requirement. For example, restraining items of mass to the load cases in MIL-STD-1290A may not afford an improvement in crash protection if the structure of large fixed wing aircraft will disintegrate well before these loads are reached in a challenging environment survivable crash scenario.
6.19 This section presents the Authority prescribed CCPDR for Defence aircraft. Unlike most other Authority prescribed design requirements in the DASDRM, the CCPDR prescribed in this section are applicable to Defence aircraft throughout the aircraft’s life-of-type, not just for acquisition.
Aircraft operating in a benign environment
Small fixed wing and rotary wing Defence aircraft having a civil or civil-derived certification pedigree – the CCPDR defined in Annex A to this Chapter.
Small fixed wing and rotary wing Defence aircraft having a military certification pedigree – the CCPDR defined in Annex A to this Chapter or the CCPDR in Annex B to this Chapter (noting that compliance with Annex B exceeds the benchmark requirements).
Large fixed wing aircraft Defence aircraft having a civil, civil-derived or military certification pedigree – the CCPDR defined in Annex A to this Chapter.
Aircraft operating in a challenging environment
Small fixed wing and rotary wing aircraft having a civil or civil-derived certification pedigree - the CCPDR defined in Annex A to this Chapter supplemented by applicable requirements defined in Annex B, where the Annex B requirements are more onerous; or the CCPDR in Annex B to this Chapter.
Small fixed or rotary wing aircraft having a military certification pedigree – the CCPDR defined in Annex B to this Chapter.
Large fixed wing Defence aircraft having a civil, civil-derived or military certification pedigree – the CCPDR defined in Annex A to this Chapter supplemented by applicable requirements defined in Annex B, where the Annex B requirements are more onerous.
6.22 The determination of CCPDR for large fixed wing aircraft that operate in a challenging environment will be dependent on the type of operations being undertaken. The CCPDR for these aircraft types and operations is likely to be a combination of Annex A plus requirements from Annex B (ie MIL-STD-1290A) that are determined to be applicable to the likely survivable crash scenarios for that aircraft type. However, in the absence of an analysis of the operating environment to establish which crash protection features warrant additional consideration or the adoption of more onerous requirements, the Authority is unable to prescribe generic CCPDR for these aircraft.
6.23 Design Requirement (Essential). Changes to the type design must not degrade the level of crash protection afforded by the extant Defence aircraft design.
6.24 Design Requirement (Essential). Changes to the type design must meet the relevant requirements of the Authority prescribed CCPDR.
6.25 Proposed changes to the aircraft configuration must retain the extant level of crash protection of the aircraft and satisfy the relevant Authority prescribed CCPDR. The Authority will not ordinarily approve a design change that results in a reduced level of crash protection from that inherent in the extant aircraft baseline. However, where such a reduction is unavoidable (eg due to a capability imperative), the shortfall must be assessed in terms of the impact on safety versus capability gains of the proposed change to establish whether reasonably practicable controls to either eliminate or further minimise the risk can be implemented. Informed risk treatment decisions can only be made if the evaluation presents a robust assessment of the magnitude of the reduction, together with options for reasonably practicable risk treatment to improve the level of crash protection. Design changes must also be evaluated against the relevant CCPDR and reasonably practicable design features that improve the level of crash protection afforded to occupants must be incorporated. Any shortfalls against the CCPDR must be managed in accordance with the requirements of DASR AMC1 to 21.A.17A.
NOTE
6.26 While the civil and military crash protection design requirements and standards referred to above include considerations for cargo carriage, these considerations are often not contextualised for the Defence operational environment. The cargo load restraint standards prescribed in Section 5 Chapter 5 of this manual have been developed specifically for the Defence military context of strategic and tactical airlift, both with and without passengers. The military standards also consider required capability outcomes and the necessary flexibility to achieve operational goals. None of these aspects feature in considerations for civil load restraint (particularly for cargo) and therefore direct application of the civil requirements may not be appropriate for Defence aircraft, depending on the aircraft’s role and type of operations.
2.27 Prior to adopting the cargo restraint requirements in Section 5 Chapter 5 as the CCPDR for a particular aircraft type, the designer must confirm with the capability manager that the context of application of the cargo load restraint requirements is consistent with the proposed Defence aircraft operational context. Further, any additional risk treatments (such as operational treatments to limit exposure of passengers to injury/death as a result of loss of cargo restraint in a survivable accident) must be considered and implemented where reasonably practicable, including the adoption of the civil-like cargo carrying requirements where practicable.
6.28 For some Defence aircraft the context of operations is not consistent with the context for which the Section 5 Chapter 5 requirements were derived. For example, the KC-30A will occasionally be required to carry Defence cargo, but the loading/unloading of this cargo is not usually required to be conducted in adverse operational conditions requiring rapid access and ease of transfer. Under these circumstances, the extant civil requirements remain appropriate as the basis for the CCPDR related to cargo carriage.
6.29 For the purposes of cargo carriage, the military cargo load restraint standards prescribed in Section 5 Chapter 5 represent the minimum standard for load restraint in military aircraft, and may be adopted in lieu of the cargo carriage restraint requirements prescribed in CCPDR subject to the following design requirements, and the considerations for carriage of cargo under DASR.ACD.
6.30 Design Requirement (Essential). For Defence aircraft undertaking military cargo carrying operations33, restraint of cargo must satisfy the load restraint limits for the cargo type and transportation mode prescribed in DASDRM Section 5 Chapter 5 Aerial Delivery of Materiel.
6.31 Design Requirement (Essential). For Defence aircraft undertaking civil-like cargo carrying operations, restraint of cargo must satisfy the load restraint limits for the cargo type and transportation mode prescribed in Authority recognised civil Airworthiness Codes.
6.32 Further guidance on implementing the crash protection requirements prescribed in this chapter can be provided by the chapter sponsor.
A. Benign Environment Contemporary Crash Protection Standard
B. Challenging Environment Contemporary Crash Protection Standard