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Aircraft Ballistic Recovery System

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Category: General General
Content source: SKYbrary About SKYbrary
Content control: EUROCONTROL EUROCONTROL

Introduction

An Aircraft Ballistic Recovery System is a rocket deployed parachute that enables an aircraft that encounters problems (such as engine failure, loss of control, icing and fuel exhaustion, etc.) to gradually descend to the ground thus giving a greater chance of survival or avoidance of serious injury. This type of system has been around for a number of years and was initially used by the USA military for recovery of their unmanned airborne surveillance platforms as the equipment carried on them was expensive and classified. National Aeronautics and Space Administration also used a similar system on the command capsules of the Apollo moon missions.

A series of pictures released by NASA showing the deployment of a ballistic recovery system

How Ballistic Recovery System Works

The system consists of a parachute and its solid fuel rocket deploying container which is usually located in the rear tail section of the aircraft’s fuselage. A cable runs from the container to an operating handle situated usually above the pilot in the roof of the cabin. The cable runs through the cabin hidden above the ceiling trim.

Once the handle has been pulled the rocket punches through a fragile section of the fuselage (similar to an air bag in a vehicle) and accelerates away at approximately 50m per second. After the parachute is completely extracted and exposed to the relative wind, it begins to inflate, generating drag forces to decelerate the airplane. The magnitude of these drag forces, or inflation loads, for a particular parachute design is a function of the airplane's weight, the airspeed at deployment, and the rate of inflation.

The drag of the aircraft causes more fragile sections along the fuselage to breakup so that when the parachute has fully deployed the aircraft will settle into and descend with the nose slightly lower than the tail. The aircraft will descend at a rate of approximately 1000 to 1500 feet per minute.

At present this system has only been fitted to light aircraft with a maximum weight of up to 3,500 kg. Some of the aircraft that the system is known to be fitted to are listed below:

Phraseology

According to UK CAA CAP 413 (RTF Manual), the following phrase should be used by pilots, where time permits, as part of the additional information within the emergency message:

“Ballistic recovery system deployed”

Safety Issues

Ballistic recovery systems contain explosives. They cannot be disarmed with sufficient safety by rescue crews or fire fighters before rescuing the occupants. This may result in:

  • calling disarming specialists, which could delay the rescue operation, or
  • putting the lives of the occupants and/or emergency rescue services at risk when evacuating or recovering the wreckage (if there are no disarming specialists present).

Factors that lead to increasing the risk include:

  • Usually, no records are kept of aircraft equipped with ballistic recovery systems. Therefore there is no way to be certain whether a particular aircraft is equipped or not.
  • When exposed to heat (e.g. due to a post crash fire), the explosives may go off.
  • The explosives may go off when heated even if they are subsequently cooled (in case chemical decomposition has already started due to the heating).
  • The explosives may go off if subject to slow continuous heating. This may happen hours after the heating has started.
  • Explosives age naturally. The process is accelerated if they are subjected to higher temperatures (e.g. 60-70 degrees Celsius). Ageing leads to instability.
  • Friction or impact may cause set off.
  • Depending on the rocket fuel and booster material (e.g. magnesium) use of water as an extinguisher can be hazardous(a chemical reaction may release hydrogen creating a highly explosive gas mixture).

Mitigations

The following measures may be used to prevent or mitigate the risks associated with armed ballistic recovery systems:

  • Clear identification that the aircraft is equipped with such a system.
  • Registry of all equipped aircraft (i.e. if an aircraft is registered with a regulatory authority, it should be clearly stated whether or not it is equipped).
  • Fitting the rockets with heat markers and adding the inspection of these markers in relevant check-lists.
  • Inclusion of residual life verification in relevant check-lists.
  • Inclusion of a cutout system that separates the igniter from the rocket. This would reduce the risk of accidentally deploying the rocket during a rescue operation.
  • Clear identification of hangars that house equipped aircraft. This would be helpful in case of e.g. hangar fire.
  • Inclusion of relevant training for pilots of equipped aircraft and rescue crews.

Guidance in Case of Fire

Note: The guidance contained in this section is not supposed to supersede or replace local procedures.

In case that a ballistic recovery system equipped aircraft is involved in fire accident:

  • if the fire is in a hangar and the temperatures reached are less 90 degrees Celsius then the heat indicators need to be checked and if they confirm that the temperature has been below 90 degrees, the emergency services can switch to standard normal operating procedures.
  • if the fire is in a hangar and the temperatures reached are above 90 degrees then
    • all parties involved should remain at a safe distance
    • the risk area should be cordoned off
    • an explosive specialist should be called
  • if an equipped aircraft is involved in an accident and catches fire then it should be cooled intensively from a safe distance
  • if an equipped aircraft is involved in an accident but does not catch fire then
    • the release cable should be blocked (e.g. cut) as close to the igniter as possible
    • a safety cover may be used to blanket the rocket so that in case of a set off the explosion is contained by the cover
  • in case of wreckage salvaging after an accident a disposal squad should be called in.

Further Reading