2.1 When operating, Defence aircraft can present a hazard to aircrew, other aircraft occupants, and persons near or under the aircraft flight path. While stationary, Defence aircraft can present a hazard to maintenance and other ground personnel. The Australian Work Health and Safety Act and the Work Health and Safety Regulations (collectively, WHS Legislation) apply to Defence aviation, and therefore Defence has a legal obligation to ensure the health and safety of these persons. The design of the Defence aircraft can, in part, contribute to Defence satisfying this legal obligation, for example:
The aircraft design can promote a safe airborne workplace for aircrew and other occupants through:
reducing the likelihood of a catastrophic in-flight mishap,
improving crash survivability for aircraft occupants,
implementing design controls for in-aircraft hazards that might injure aircraft occupants, and
implementing design controls for in-aircraft hazards that might affect the future (post-flight) health of aircraft occupants.
The aircraft design can promote the safety of persons near or under the aircraft flight path through:
reducing the likelihood of a catastrophic in-flight mishap, and
reducing the ground impact energy (mainly relevant to uncrewed aircraft).
The aircraft design can promote the safety of persons in close proximity to a stationary aircraft through:
implementing design controls for aircraft hazards that might injure ground personnel,
implementing design controls for aircraft hazards that might affect the future health of ground personnel, and
incorporating aircraft maintenance instructions that identify reasonably foreseeable hazards to maintenance personnel and present safe maintenance practices.
2.2 Airworthiness, by its nature, focuses primarily on an aircraft’s suitability for flight, and consequently airworthiness design requirements have a similar focus. Airworthiness design requirements will therefore make a substantial contribution to those elements in paragraph 2.1 that are directly related to suitability for flight, but a lesser, or perhaps no, contribution to the remainder. For designers to execute their statutory responsibilities under the WHS Act (for example as required under Sections 22 and 24), they must comprehensively understand the contributions and limitations of airworthiness design requirements in ensuring the health and safety of persons affected by Defence aircraft.
2.3 This chapter examines the extent to which Airworthiness Codes, supplemented by the airworthiness design requirements in Sections 2 and 3 of this manual, can contribute to Defence’s statutory obligation to ensure the health and safety of persons affected by Defence aircraft. It also suggests how airworthiness design requirements might be supplemented to further discharge this obligation.
2.4 Airworthiness Authorities, both civil and military, commonly define ‘airworthiness’ in terms of an aircraft’s suitability for flight. Consequently, the civil and military Airworthiness Codes presented in Section 1 Chapter 3 of this manual focus firmly on achieving safe flight and landing (ie achieving an airworthy aircraft). At face value, this limited scope appears to address only a small subset of the hazards an aircraft could present to the health and safety of occupants. However, this is not necessarily the case. Airworthiness Codes can and do ‘incidentally’ promote the wider health and safety of aircraft occupants, while aircraft maintenance data can promote the safety of personnel on the ground. This section expands on these concepts, and identifies the health and safety delta that Duty Holders under the WHS Act must address.
2.5 The Airworthiness Codes in Section 1 Chapter 3 of this manual, when supplemented by the airworthiness design requirements in Sections 2 and 3, will substantially ensure the risk to occupants due to a catastrophic aircraft failure and subsequent ground impact, is minimised so far as is reasonably practicable. This is because the Codes and Authority prescribed supplementation are regularly reviewed and updated to reflect contemporary aviation industry benchmark requirements. As such, compliance with the associated design standards when coupled with a System Safety program contributes to satisfying a Duty Holder’s responsibility to exercise knowledge of risks and ways of eliminating or otherwise minimising those risks.
2.6 Airworthiness Codes also recognise that properly functioning aircrew are an essential contributor to an airworthy aircraft. Consequently, they include design requirements that protect aircrew from a wide range of injuries, such as electric shock, burns, hypoxia, and so on. Fortuitously, design requirements for crash protection also contribute to protecting aircrew from injuries, since they require effective seatbelts (which can also protect from harm due to turbulence), an absence of sharp protrusions that might impede emergency egress (which protects aircrew during normal operations), restraint of items of mass (which also protects against harm due to movement of these items while airborne), and so on. Summarised, modern civil and military Airworthiness Codes make a substantial contribution to Defence’s confidence that the risk to aircrew of injury is minimised so far as is reasonably practicable.
2.7 The protection of other aircraft occupants from injury, on the other hand, is less straightforward. In civil Airworthiness Codes, the protection of passengers from injury is still covered, albeit several design requirements are less rigorous for passengers (for example, harness seatbelts are not a requirement for passengers, there are different oxygen supply requirements for passengers, and so on). Despite these minor differences, however, modern civil Airworthiness Codes will normally cater well for the protection of passengers from injury. Military Airworthiness Codes, on the other hand, can be less prescriptive for passengers and more open to tailoring to meet capability requirements, so the protection of passengers from injury is not necessarily well covered.
2.8 Summarised, aircraft meeting the design requirements of this manual provide a substantial contribution to Defence’s confidence that the risk of injury to aircrew will satisfy WHS Legislation requirements. Similar confidence is obtained for the risk of injury to passengers where civil Airworthiness Codes are employed, but supplementation may be needed for military Airworthiness Codes.
2.9 Readers will note some equivocation in paragraphs 2.5-8 as to whether aircraft meeting the design requirements in this manual will comprehensively satisfy Defence’s statutory obligations to ensure the safety of aircraft occupants during flight. This equivocation is necessary because the Authority-prescribed reputable standards are not the only consideration when concluding the risks inherent in an aircraft design have been minimised so far as is reasonably practicable. Additional considerations are examined in annexes A and B. Furthermore, for a risk to be minimised so far as is reasonably practicable, there must be effective consultation, coordination and cooperation on risks between all concurrent Duty Holders.
2.10 The preceding paragraphs focused on the protection of aircrew and other occupants from injury (ie an immediate ill effect while the aircraft is in operation), because this is the purview of airworthiness. Airworthiness, and therefore Airworthiness Codes, normally will not cover the future ill effects to the health of aircrew and other occupants, for example due to:
chemical hazards (eg carcinogenicity, gradual toxicity, etc);
biological hazards;
physical hazards (eg long-term effects of aircraft vibration);
ergonomic hazards;
personnel radiation hazards;
acoustic hazards; and
other hazards that may have a future ill effect on the health of aircrew and other occupants.
2.11 Consequently, Duty Holders will need to prescribe additional design requirements that specifically address future effects to the health of aircraft occupants. Guidance on this issue is presented later in this chapter.
2.12 The design of an aircraft can promote the safety of persons near or under the flight path through reducing the likelihood of a catastrophic in-flight mishap (and consequently ground impact), and reducing the ground impact energy. Neither will be specifically covered in this chapter, since the former is well covered through assuring the safety of aircraft occupants, while the latter is mostly unique to uncrewed aircraft (see Section 4 of this manual).
2.13 Stationary aircraft can present a hazard to aircraft maintenance personnel and other personnel in close proximity to the aircraft. The design of an aircraft can promote the health and safety of these people through:
an absence of hazards that might cause injury (eg sharp edges, protrusions, unprotected hot surfaces, etc);
an absence of hazardous materials that might cause future ill effects to health; and
the Authorised Maintenance Data accompanying the aircraft design can identify significant hazards to maintenance personnel and present sensible maintenance practices.
2.14 None of these outcomes is within the scope of ‘airworthiness’. Consequently, Duty Holders will need to prescribe additional design requirements that specifically address these issues. Guidance is presented in the next section.
2.15 There are many hazards to aircraft occupants and people on the ground that are not within the purview of ‘airworthiness’. Consequently, additional design requirements must be prescribed, and analyses completed, if Defence is to meet its statutory obligations for new aircraft. The remainder of this chapter provides guidance to Duty Holders on prescribing additional design requirements, beyond those dedicated to airworthiness, to ensure the health and safety of affected persons.
2.16 Paragraph 2.10 of this chapter concluded that airworthiness design requirements do not satisfactorily address the future effects on the health of aircraft occupants. Where Defence is acquiring off-the-shelf aircraft, annex B provides guidance to Duty Holders on how to ensure future health risks are eliminated or otherwise minimised so far as is reasonably practicably. Where Defence is acquiring developmental aircraft, the ‘Air Force Work Health and Safety Management System’ including relevant best practice standards detailed in the Air Force Safety Manual may be used to derive additional design requirements for the aircraft. Further advice may be obtained from specialist Defence agencies with WHS domain expertise, including:
the Defence Work Health and Safety Branch,
HQAC A9 – Air Force Safety (AFS), and
the Institute of Aviation Medicine (AVMED).
2.17 System Safety and WHS. A common, but potentially incorrect, proposition is that Defence’s WHS responsibilities will be satisfied if an aircraft System Safety Program (SSP) has been established. While a SSP can make a positive contribution to achieving an aircraft design that satisfies statutory requirements, it is by no means automatically comprehensive. Positive contributions can include the following:
SSPs should implement an enduring system for recording and managing hazards, which is a statutory requirement.
Some SSPs can include tools for identifying hazards to personnel, for example the Operating and Support Hazard Analysis (OSHA) and Health Hazard Analysis (HHA) tasks in MIL-STD-882.
SSPs can impose an ‘order of precedence’ for treating hazards, and many of these will satisfy the WHS Legislation’s ‘hierarchy of controls’.
2.18 However, consider the following:
System safety programs will normally assume that hazards are acceptable when their likelihood and/or consequence is sufficiently low, or in some cases where residual risk has been retained at an appropriate level. This approach is quite different to the requirements of the WHS legislation, which expects risks will be eliminated, or if this is not reasonably practicable, then the risk will be minimised so far as is reasonably practicable. Furthermore, this risk minimisation should iteratively continue until the cost of further risk minimisation is grossly disproportionate to the benefits, regardless of the residual ‘risk level’.
The usual SSP tools such as OSHA and HHA merely provide a framework and some general guidance for identifying WHS hazards; application of these tools does not inherently result in the identification or effective management of all hazards.
The WHS benchmarks defined in overseas SSP documents (including the MIL-STD-882 OSHA and HHA) are relevant to their local statutory requirements and policies. These will certainly be different to Australian WHS Legislation and Defence WHS policies.
2.19 Summarised, an aircraft SSP can make a contribution to Defence meeting its statutory responsibilities, but only if it has been specifically designed to achieve this.
2.20 Paragraphs 2.13-14 of this chapter concluded that stationary aircraft can present hazards to aircraft maintenance personnel and other personnel in close proximity to the aircraft, but these hazards are not addressed by airworthiness design requirements. Paragraph 2.16 presented guidance to Duty Holders for achieving an aircraft design that satisfies statutory obligations, and that guidance is equally relevant here.
2.21 Duty Holders should also produce Authorised Maintenance Data for the aircraft that contributes to the health and safety of maintenance personnel by identifying hazards and promoting safe maintenance practices. This can be particularly complex to achieve, since it requires a holistic assessment of the compatibility of the ICA processes with Defence maintainer training, local maintenance processes, maintenance policy, WHS Legislation, and so on. The information presented in the Air Force Safety Manual may assist Duty Holders in this endeavour.
2.22 As indicated previously in this chapter, airworthiness design requirements help Defence meet its statutory obligations. However, airworthiness design requirements focus primarily on the suitability for flight of an aircraft, whereas aircraft can present many hazards outside of this narrow scope. Consequently, additional design requirements will need to be prescribed. Further guidance on these additions should be sought from Defence’s WHS specialist organisations, including the Defence Work Health and Safety Branch and HQAC A9 – Human Performance and Safety.
A. Exercising ‘Reasonable Knowledge’ in Aircraft Design
B. Guidance for Defence Duty Holders when Acquiring Off-The-Shelf Aircraft