This assessment examines the hazards, risks and controls that relate to incidents involving aircraft and includes accidents and fires.

This assessment must be read in conjunction with other, related, assessments for example, those for explosives and chemicals.¹

Reference is made throughout the document to GRAs and other technical sources.

As with all GRAs this assessment provides a starting point for brigades to conduct their own assessments within the context of local conditions and existing organisational arrangements.

The degree to which personnel will be subject to the risk of injury from incidents involving aircraft depends upon the following factors:

• crash rates
• aircraft construction
• fuel
• other Inboard hazards
• manual handling

2.1.1 For the purposes of crash risk assessments it is necessary to divide aircraft into different categories because of the different flying characteristics and reliability of different types of aircraft.

Impact characteristics such as mass and velocity can be very different from one aircraft to another, which affects the consequences of a crash. The categories are as follows:

• LIGHT CIVIL AIRCRAFT (category 1) - fixed wing aircraft generally falling into the Civil Aviation Authority (CAA) classification of less than 2.3 tonnes (te) maximum take-off weight authorised (MTWA). This category also includes military light aircraft used for training which are less than 2.3 te MTWA.
• HELICOPTERS (category 2) - all civil and military helicopters.
• SMALL TRANSPORT (category 3) - fixed wing aircraft covering the mass range 2.3 te to 20.0 te MTWA, including civil and military transport aircraft.
• LARGE TRANSPORT AIRCRAFT (category 4) - any other fixed wing aircraft, civil or military, not covered in the light aircraft, small transport or military combat and jet trainer categories.
• MILITARY COMBAT AND JET TRAINERS (category 5) - all military fixed wing aircraft with MTWA up to 40 - 50 te used for, or capable of, acrobatic style flying.

2.1.2 The likelihood of aircraft crashes can be calculated from past statistical data, the HSE has published "crash" rates for specific sites and types of aircraft².
Aircraft activity varies with time, in terms of the types of aircraft in use and the numbers involved. both generally and at specific airfields. Aircraft reliability, i.e. the probability of an accident per landing/take-off or per in-flight km, may also change with time and affect crash rates.

2.1.3 In recent years changes in defence policy in western Europe have led to a decline in military aircraft activity in the UK. This can be measured both in terms of the number of low-level sorties annually, and the run-down of USAF activity in the UK. Military Combat Aircraft (MCA) probably pose the greatest potential risk to major industrial installations in the UK, because of their relatively high masses and velocities and the nature of low-level sorties. It is particularly important, therefore, to monitor changes in MCA activity and the subsequent effect, if any, on crash rates.

2.1.4 The last revision to background crash rates in the UK was carried out in 1995 covering accident data up to and including 1994. For 1985 - 1994, the total number of crashes was 56, or 5.6 crashes per year. This figure includes both civil and military crashes and a mid-air collision counted as two impacts. The number of crashes over England, Scotland and Wales are as follows:

England: 48
Scotland: 7
Wales: 1

2.2.1 Types and size of aircraft are very diverse, ranging from single seat micro-lights to wide bodied civilian passenger aircraft. The risks to firefighters are normally the same, as methods and materials used in the construction of aircraft tend to be standard, due to their properties.

2.2.2 Many types of alloys are used, duralumin, alclad and magnalium are used for skin surfaces, spars and stiffeners. Where stronger lightweight metals are required then magnesium , stainless steel and titanium alloys are used.

2.2.3 The major components of modern aircraft manufacture are either Man Made Mineral Fibres (M.M.M.F.) or Metal Alloy. The term M.M.M.F. describes a wide range of materials which utilise the inherent strength and durability of woven fibres bonded together with resin. Carbon Fibre Reinforced Plastic, Glass Fibre Reinforced Plastic, Composites and Kevlar (trade name) are common names used to describe these materials.

Risk to personnel arises from the decomposition of the material both during and after an aircraft fire. Carbon fibre materials will be left in a friable condition easily liberated when touched. The fibres are unlikely to be respirable in size but could easily causeneedle stick injuries and traumatic dermatitis similar to that associated with fibreglass.
Carbon fibres are capable of absorbing all of the products of a post crash fire and if touched, will act as an injection carrier enabling these products to enter the body. Additionally, the decomposition of the material may also result in the liberation of isocyanate. There is the possibility that the material may plume following an air crash and be carried some considerable distance downwind.

2.2.4 Flammable liquids, radiation sources (including microwaves), pressurised systems, oxygen containers, electrical sources, explosives, the noise and moving parts of engines Cjet and propeller) are all found in aircraft construction and propulsion systems³.

A common hydraulic fluid used throughout aircraft is "Skydrol", this is very irritating to the eyes and skin.

2.2.5 The massive weight of some civil and military airframes combined with the weight of the payload and the speed of travel may result in the compromise of underground services. When an impact takes place at an airport underground services may include fuel lines

2.3.1 These fall broadly into two types -(a) Gasoline (petrol), and (b) Kerosene.

2.3.2 Avtur, Avtag, Avcat kerosene and Avgas (graded) Petrol are the more common types of fuel used. They have different properties. Information regarding types used locally should be recorded during the familiarisation visits.

2.3.3 The most dangerous state for any fuel is in the form of a fine spray mist.

• rigid - Made from Aluminium Sheet
• integral - Made from the compartments of the Airframe Structure
• flexible - Made from Plastics or other Man Made Fibre
• auxiliary - Extra tanks fitted under the wings or fuselage

There are different types used for different types of plane, The most commonly used ejection seats are the Martin Baker type. Ejector seats are operated by explosive charges which are located in the base of the seat.

Planes fitted with ejection seats are also fitted with a means to access the canopies, this can be a canopy jettison mechanism and/ or a miniature detonating cord both of which can be hazardous to firefighters.

There may also be the likelihood of military weapons utilising depleted uranium4 both as a tip to weapons and as balancing weights on wing tips. Depleted uranium poses a similar hazard to personnel as any other radiation source.

Powerful laser target designators may also be fitted to some aircraft. The biologicalhazards from lasers depend on the wavelength, the power or energy of the beam, the pulse length and the exposure duration. The eye is the main organ at risk from laser radiation but skin damage may result if the power and beam power density (irradiance) is high enough. There could also be a potential fire hazard with high power lasers. Other toxic risks may exist in relation to the basing medium or materials of construction of the laser, e.g. some dyes, beryllium tube linings etc⁵.

In civil aircraft the payload will either be:

• passengers
• cargo
• a combination of both

The risks associated with passengers will range from the chaos associated with a mass egress to the biological, psychological and manual handling hazards involved with body recovery.

Cargoes may include any goods, materials or livestock that require transportation. Inherently hazardous cargoes may include the full range of hazardous substances, radioactive substances, pesticides, explosives and flammables.

Military transport aircraft may also carry a full range of hazardous cargoes, for example, a transport carrying ground tanks may also be carrying diesel fuel and depleted uranium shells⁶.

When aircraft crash off the airfield access is normally restricted. This often requires heavy equipment to be transported over difficult terrain, with the subsequent risk of injury to personnel.

Notwithstanding the location of the incident once aboard an aircraft personnel will be manoeuvring themselves and their equipment in very restricted areas. This will lead to an increased risk of long term musculoskeletal injury.

Brigades will need to consider the local control measures that are proportional to the nature and degree of risk within their area. Key measures may include:

Liaison with local flight authorities e.g. CAA establishments, regional civil and military air traffic control will provide an indication of the type and frequency of aircraft over flying the brigades area. Where there is an airport in the area, closer liaison including training will be of benefit. Practical training could be conducted with and without air authority crews to simulate crash and fire situations both on and off the immediate area of the airport.

3.2.1 Consideration must be made of the terrain and wind direction before a firefighting attack can be made. The exact location and extent of the incident must be established and cordons and safe areas set up.

3.2.2 Gases within their flammable range will drift downwind from a crash site. Large amounts of toxic smoke and fumes will be produced by any aircraft fire. In order to minimise risk of igniting gases or being affected by toxic smoke, appliances must be parked upwind and in a position away from the danger from free flowing fuels.

3.2.3 When approaching the aircraft consideration must be given to the propellers and jet engine intakes and exhausts as engines may still be running.

3.2.4 Spray branches should be deployed on the fuselage to assist with rescues.

3.2.5 Foam should also be used to cover any fuel (Avgas etc) that will be leaking within the surrounding area.

3.2.6 A foam blanket must be laid to reduce the risks from unburned fuel to personnel approaching the aircraft.

Effective communications must be established and maintained:

• with Brigade Control
• at the scene
• with other agencies

3.3.2 This will allow the IC to request specialist advice, control operations at the scene, and use the media to for example, inform the public, who may be unintentionally hampering operations.

3.3.3 The IC should consider the use of intrinsically safe (I.S.) communications equipment where the possibility of a flammable/explosive atmosphere may exist.

3.4.1 Breathing Apparatus must be worn and controlled in accordance with Technical Bulletin 1/978.

3.4.2 BA must be donned in fresh air with consideration being taken of the cordon area and the distance from the scene of the incident. Stage 2 Control should be considered as a priority and adequate personal protection with decontamination procedures being implemented.
Wearers should not enter fuel spillage areas but consideration must be given to rescues.

3.4.3 IC's must consider the physiological affects of wearing BA in chemical protection suits and wearers must be monitored and rotated frequently.

LIST OF CONSIDERATIONS FOR I.C.s AT INCIDENTS INVOLVING AIRCRAFT FIRES.

• Dynamic risk assessment to be undertaken immediately on arrival.
• Consider evacuation of non-operational personnel to a distance of 300 metres.
• The slope of the ground and the wind direction must be considered when siting the appliances.
• Ensure oncoming appliances have adequate route directions
• Type of Aircraft Military
  - smaller numbers of people involved
  - danger from ejection seats and canopies
  - dangers from weapon and defence systems (explosive)
  - nuclear risk (radiation)
  
  Civilian
  -larger numbers of life risk and involvement
  -large fuel loads on large passenger planes
  -cargo unknown - consider hazardous materials.
  
• All types of aircraft.- A danger exists from the air intakes and exhausts of jet engines and the rotating blades of aircraft fitted with rotors and propellers.
• Extreme caution should be exercised when approaching any type of aircraft.

• Isolate the fuselage from the fire and heat
• Attack from up wind.
• Spray along the line of the fuselage, cooling and driving free fuel away from the occupied portion of the plane.
• Protect rescue and exit paths. When an adequate supply of foam is available commence a foam attack
• Breathing apparatus and adequate personal protective clothing must be worn
• Consider decontamination requirements