8.1 Smoke and fumes in Defence aircraft, particularly from electrical fires which can generate substantial smoke and toxic gases, can rapidly incapacitate crew and passengers. The type and the severity of the event, crew actions and the degree of their success, can all influence the severity of the outcome of smoke and fumes events.
8.2 While the Authority recognised Airworthiness Codes defined in Section 1 of this manual inherently prescribe some smoke and fumes protection requirements, these are not sufficiently detailed to establish the adequacy of smoke and fumes protection for Defence aircraft crew and passengers. For example, the civil Codes largely prescribe smoke and fumes protection requirements on the basis of the aircraft type, while some military Codes prescribe requirements (if any) on the basis of an aircraft’s operational role. Consequently, the Authority prescribes airworthiness design requirements for smoke and fumes protection to supplement the Airworthiness Codes and provide a basis for verifying the acceptability of Defence aircraft smoke and fumes protection measures.
8.3 This Chapter prescribes Authority supplementation to the smoke and fumes protection elements of recognised civil and military Airworthiness Codes. Importantly, the airworthiness design requirements in this Chapter are not suitable for application in isolation from an Airworthiness Code. The Authority’s requirements for the application of recognised Airworthiness Codes are defined in Section 1 of this manual.
8.4 Smoke and fumes protection is required to prevent the incapacitation of flight crew and other aircrew, and to protect the breathing of passengers, during smoke and fumes events in Defence aircraft. Smoke and fumes protection is afforded to aircraft occupants through a combination of the use of materials that minimise the generation of smoke and fumes when exposed to fire or heat sources, and the implementation of personal protective measures for occupants, that enable continued safe operation of the aircraft in the presence of smoke and fumes. This chapter only covers the latter of these two aspects. The use of materials that minimise the generation of smoke and fumes is covered in Section 2 Chapter 7 Fire Protection and Section 3 Chapter 8 Electrical Power Systems.
8.5 Defence aircraft smoke and fumes protection requirements are influenced by two primary considerations: the worst case duration of a smoke and fumes event; and the elements of the design that protect the crew and passengers from adverse physiological effects of smoke and fumes. The Authority prescribed smoke and fumes protection design requirements in this Chapter define the basis for establishing the ‘worst case smoke and fumes event duration’ for Defence aircraft, and whether the design affords an adequate level smoke and fumes protection for:
the flight crew responsible for flying the aircraft
‘emergency response crew’ (eg crew involved in locating the source, extinguishing fire, aiding passengers with breathing equipment, and so on)
passengers and other crew.
8.6 The worst-case smoke and fumes event duration is the time taken to identify the source, combat the source and reduce the smoke and fumes to a level where safe flight and landing and passenger safety is not compromised. Civil and military design standards do not prescribe minimum durations for smoke and fumes protection of aircraft occupants. Consequently, the Authority requires that the worst-case smoke and fumes event duration is established, to ensure that smoke and fumes protection measures remain effective throughout a smoke and fumes event.
8.7 Design Requirement (Essential). The worst-case smoke and fumes event duration for a Defence aircraft must be established.
8.8 An evaluation of the likely sources of smoke and fumes in occupied spaces of Defence aircraft must be conducted, in conjunction with operational representatives, to establish the worst-case smoke and fumes event duration for all aircraft operations. While a minimum smoke and fumes protection ‘time’ is not prescribed in Authority recognised civil or military Airworthiness Codes, some civil design requirements prescribe requirements to ensure ‘breathing protection’ for between ten and fifteen minutes. These times are largely based on the requirement to provide supplemental breathing during an emergency descent following loss of aircraft pressurisation, until the aircraft reaches an altitude at which breathing can be sustained. While these timeframes may also represent the worst-case duration of a smoke and fumes event for some aircraft, for others they may be excessive or inadequate.
8.9 The worst-case event duration for a particular Defence aircraft will depend on the configuration, role and operating environment of the aircraft (for example, a helicopter is likely to have a much lower worst-case event duration, given its lower operating altitude and ability to land in many locations, than a large fixed wing aircraft). Nevertheless, recorded smoke and fumes events in civil and military aircraft suggest that a suitable benchmark worst-case event duration is twenty minutes, and this should be adopted where a bespoke duration for a particular Defence aircraft type cannot be established. Where a smoke and fumes event continues beyond twenty minutes duration, the cause of the event is likely to result in a non-survivable accident and smoke and fumes protection for occupants beyond this duration is therefore of little benefit.
8.10 Flight crew must be able to continue to communicate (with each other, passengers and other external parties, eg ATC) and to safely operate the aircraft, and emergency response crew must be able to conduct emergency response procedures or undertake fire fighting activities, during a smoke and fumes event. The airworthiness design requirements prescribed by other NAAs in Authority recognised Airworthiness Codes do not include smoke and fumes design requirements with sufficient detail to ensure that the adequacy of protective measures can be verified for the Defence aircraft configuration, role and operating environment. Therefore, the Authority has prescribed the following supplementation for flight and emergency response crew smoke and fumes protection in Defence aircraft.
8.11 Design Requirement (Essential). For the worst-case smoke and fumes event duration, flight crew smoke and fumes protection must provide:
clear vision
the ability to breathe
the ability to safely operate the aircraft
the ability to communicate with other crew members and passengers, and to use aircraft radio equipment while protection measures are in use.
8.12 Design Requirement (Essential). Emergency response crew smoke and fumes protection must provide:
clear vision for the worst-case smoke and fumes event duration
the ability to breathe for the worst-case smoke and fumes event duration
portability, to enable movement about the aircraft and to conduct emergency procedures for fire fighting, for the predicted period of time required to complete the emergency procedure or fight a fire
the ability to communicate with other crew members and passengers while protection measures are in use.
8.13 Inadequate flight crew smoke and fumes protection may result in an otherwise survivable smoke and fumes event becoming catastrophic, if the crew are unable to continue to safely operate the aircraft. Inadequate emergency response crew smoke and fumes protection may result in an initially minor smoke and fumes event becoming an uncontrollable emergency if the crew is unable to respond appropriately to the initial onset of smoke/fumes. The flight and emergency response crew smoke and fumes protection measures in Defence aircraft must be evaluated and the adequacy of crew breathing, vision, aircraft operation and communication must be verified for the worst-case smoke and fumes event duration.
8.14 Flight and emergency response crew smoke and fumes protection may be provided by evacuation of smoke and fumes from occupied spaces, isolation of the flight deck and/or the provision of protective breathing equipment. Where protective breathing equipment is fitted to Defence aircraft, it is likely to be the primary means by which smoke and fumes protection is afforded for vision and breathing while ensuring the crew can continue to safely operate the aircraft (or combat the source) and communicate where required. When protective breathing equipment is required to satisfy the Authority prescribed design requirements for flight and emergency response crew smoke and fumes protection, the requirements defined in FAR/CS 25.1439 and FAR 121.337 may be used as a guide for verifying the adequacy of the equipment.
8.15 Breathing protection, necessary to sustain life, must be provided to passengers during a smoke and fumes event. While the Authority recognised civil Airworthiness Codes include emergency oxygen supply requirements for passengers, these systems are generally only required to support breathing in the event of depressurisation, and may not be intended to support breathing during a smoke and fumes event. Consequently, such systems are usually designed to afford breathing protection for the minimum time required to descend to an altitude at which breathing can be sustained. The Authority recognised military Airworthiness Codes do not include any design requirements for protection of passenger breathing during smoke and fumes events. Therefore, the Authority has prescribed the following supplementation for passenger smoke and fumes protection in Defence aircraft.
8.16 Design Requirement (Essential). Passenger smoke and fumes protection must provide the ability to breathe for the worst-case smoke and fumes event duration.
8.17 Passengers and other crew are not normally required to participate in emergency procedures until the aircraft has landed. Nevertheless, passengers must be physically capable of evacuating the aircraft once it is safe to do so and, therefore, cannot become prematurely incapacitated during smoke and fumes events. Passenger breathing protection may be accomplished via supplemental breathing systems, filtration of cabin air or evacuation of smoke and fumes. The passenger smoke and fumes protection measures in Defence aircraft must be evaluated and the adequacy of passenger breathing must be verified for the worst case smoke and fumes event duration. Where evacuation of smoke and fumes from occupied spaces is proposed as the sole means of affording passenger breathing protection, the adequacy of the evacuation means must be evaluated and confirmed to provide the required protection.
8.18 Military aircraft fitted with ejection seats often operate at cabin altitudes for which supplemental breathing systems are required to support safe aircraft operation. These systems are likely to satisfy the smoke and fumes protection requirements for breathing protection for the worst-case smoke and fumes event duration, and the ability to communicate. However, the equipment worn by flight crew in these aircraft may not satisfy the requirement to ensure adequate vision is maintained (eg helmet visors may not ensure that clear vision is maintained during a smoke or fumes event). The Authority recognised military Airworthiness Codes do not include requirements for protection against the effects of smoke and fumes in ejection seat aircraft (other than breathing protection).
8.19 Ultimately, the crew has the option of ejecting if smoke and fumes prevent continued safe aircraft operation and, therefore, establishing the worst case smoke and fumes event duration and conducting a detailed evaluation of the smoke and fumes protection afforded by ejection seat aircraft designs is not normally warranted. However, limiting the circumstances under which ejection is necessary provides safety benefits in terms of reducing the likelihood of injury during ejection, and may improve capability through reducing the number of ejection events. Therefore, the Authority has prescribed the following supplementation for crew smoke and fumes protection in Defence ejection seat aircraft.
8.20 Design Requirement (Recommended). Additional smoke and fumes protection measures that potentially limit the circumstances under which an ejection may be required should be identified and implemented where reasonably practicable.
8.21 Further guidance on implementing the smoke and fumes protection requirements prescribed in this chapter can be provided by the chapter sponsor.