Hazard Working around military aircraft
Knowledge and understanding
|Working around military aircraft||
Understand all associated hazard knowledge
Military aircraft mainly operate from military aerodromes but may also be found at civilian aerodromes. Fire and rescue services may need to attend an incident involving a military aircraft; this is most likely to be off aerodrome.
Military aircraft include:
- Small aircraft
- Unmanned aircraft systems (drones)
- Large passenger or cargo aircraft
- Helicopters – see separate hazard: Working around helicopters
Some military aircraft may be similar in appearance to civil aircraft. However, additional hazards for military aircraft could include:
- Unconventional interior configurations
- Aircraft assisted escape systems (AAES)
- Explosive armaments
- Weapon systems
- Passive and active radar systems
Military aircraft should be left undisturbed, including jettisoned aircraft assisted escape systems, until the arrival of the Defence Accident Investigation Branch (DAIB).
Aircraft assisted escape systems
Aircraft assisted escape systems (AAES) present a significant hazard to personnel attending a military aircraft incident. Aircraft assisted escape systems (AAES) means collectively:
- Ejection seats
- Equipment fitted to the ejection seat, including emergency escape parachutes
- Systems for clearing the ejection path from the aircraft, including associated mechanisms operated by explosives
- Personal survival packs
An ejection seat is a system fitted to most military advanced trainer and fast jet aircraft; they can also be found in private ex-military aircraft. If activated in an emergency by the aircrew, the ejection seat is propelled from the aircraft by a pyrotechnic charge or rocket motor, carrying the occupant with it. Once clear of the aircraft, the system will automatically deploy a parachute. Once initiated, the ejection sequence is fully automatic and cannot be stopped.
When an aircraft is parked on the ground, safety pins are used to prevent the accidental actuation of the ejection seat or the ejection mechanism. However, when attending an incident involving a military aircraft, assumptions should not be made about the status of ejection seats; if ejection seats are still in the aircraft they could activate at any time.
A military aircraft cockpit is covered and protected by a canopy. Canopies can weigh in the region of 100kg and are constructed from a strong, heavy and usually transparent material.
The emergency canopy release may be activated accidentally or intentionally by the aircrew. It may also be jettisoned or fragmented by explosive charges, to provide a clear route for the ejection seat if activated.
Explosive armament stores
Missiles, rockets and bombs found on military aircraft will contain varying amounts and types of highly explosive material. Explosive armament may not explode during a crash, but may behave unpredictably.
Electro-explosive devices may be accidentally initiated by radio or radar frequency electromagnetic radiation.
If an aircraft accident involves nuclear weapons or materials, the Defence Accident Response Organisation will assume command of the accident.
Defensive systems are very sensitive and can activate unexpectedly. They may include:
Chaff, which may be deployed from the aircraft with explosive force, and then distributed through the air by a small explosive device
Defensive flares, which can provide an ignition source, burn at a very high temperature and produce a light bright enough to cause significant eye damage
Small arms and gun ammunition
Several types of small arms and gun weapon systems may be found fitted to military aircraft, depending on the aircraft’s specification and role. Gun ammunition carried on aircraft is usually stored in safe containers.
Apart from live ammunition, weapon systems may also discharge pyrotechnics or blank rounds. Gun ammunition may ‘burst’ unexpectedly if exposed to fire or impact, and weapons may become detached from the aircraft during accidents.
Pyrotechnic devices may be found on military aircraft including, signal cartridges, distress flares and smoke markers. They will commonly incorporate a metal tube containing explosive material that is crimped at one end. When ignited it will emit flame and sparks at the open end.
Pyrotechnic devices can be used to ignite rocket motors, to deploy underwing weapons, or to jettison external fuel tanks; they may also be located in fire suppression systems around the aircraft. Marine flares and smoke markers may be ejected from the aircraft with some force, manually or automatically, following a crash or on contact with water.
Personal flares may be found within the aircrew survival kit; they can be an additional hazard when performing rescues or where bodies have to be recovered.
As military aircraft may operate at high altitudes, a breathable oxygen supply is provided. Oxygen will often be stored under pressure in cylinders or automatically generated on demand. If aircraft are involved in fire, there is a risk of explosion of oxygen.
Aviation fuel and specialist fuels
Military aircraft generally use the same types of aviation fuels that commercial aircraft use, with some additives. Some aircraft can be fitted with auxiliary external fuel tanks, which can be jettisoned in an emergency.
Mono fuels are fuels that can support combustion without an external air supply, as the chemical make-up of the substance contains its own oxygen. They are usually found in small quantities on aircraft and are used to power emergency power units, or as propellants for missiles.
Infrared and laser guidance systems
Modern weapon systems used on military aircraft may be fitted with infrared guidance systems for weapons targeting. Forward Looking Infrared (FLIR) and Sideways Looking Infrared (SLIR), are often positioned behind a glass vision panel. Military laser guidance systems, operate at a high intensity for targeting purposes. These emissions can be damaging to delicate eye tissues and personnel should be aware of the dangers of looking directly into glass panels located on the aircraft, until it can be confirmed that all systems have been isolated. Although these systems are non-ionising, most military aircraft will carry some form of ionising radiation.
Infrared or laser guidance systems have to be manually selected by the aircrew and are unlikely to be activated during an incident. Aircraft safety systems should automatically isolate weapon firing and release circuits in emergency situations.
Radar on military aircraft is primarily for detection and surveillance. These radar units operate on differing wavelengths and at much greater power output than civilian aircraft.
Externally mounted dish scanners are used on some aircraft. In normal operating mode, the dish rotates. However, if the dish is not rotating the system may still be active.
EMFs may interfere with fire and rescue service communications including radios, mobile phones and telemetry systems. For further information see Industry: Electromagnetic fields (EMFs).
Aircraft arresting systems
Two systems may be installed at military aerodromes. They are designed to arrest aircraft landing on short runways, temporary runways or in an emergency. They use a cable spanning the runway or a net positioned at the overrun of the runway.
The cable system, known as arrestor gear, consists of a single cable engaged by a hook fitted to military aircraft. During normal arrestment, the tail hook engages the wire and the aircraft's kinetic energy is transferred to damping systems.
Arresting barrier nets stop an aircraft by absorbing its forward momentum. These nets are raised remotely by air traffic control in an emergency. Both systems involve steel cables, which may be under stress during an aircraft arrest.