Question

CASE STUDY A pilot was taxiing his air-force jet when the ejector seat fired, sending him upwards to then crash down onto the airfield, where he died from the impact injuries. Ejector seats are designed to enable a pilot to escape from a disabled aeroplane. When activated by the pilot (that is the normal way they work) a rocket pushes the seat and pilot out of the aircraft and at the top of the trajectory a parachute deploys to bring the pilot to the ground safely. This seat was not designed to enable a safe ejection at ground level, as the parachute would not have time to deploy before the seat hits the ground. Use the search term “RAF Ejector Seat” to discover a host of web sources for information on this tragic case i. Define the appropriate Event and draw, with the brief written explanation, a Mechanism analysis logic diagram. [25 marks] ii. Determine and explain your choice of the ‘questions’ which you would use to provide structure to the Outcome process and draw an Outcome Analysis diagram for the case based on those questions. [25 marks]

Answer 1

The purpose of an ejection seat is pilot survival. The pilot typically experiences an acceleration of about 12–14g. Western seats usually impose lighter loads on the pilots; 1960s–70s era Soviet technology often goes up to 20–22 g (with SM-1 and KM-1 gunbarrel-type ejection seats). Compression fractures of vertebrae are a recurrent side effect of ejection.

It was theorised early on that ejection at supersonic speeds would be unsurvivable; extensive tests, including Project Whoosh with chimpanzee test subjects, were undertaken to determine that it was feasible.^[10]

The capabilities of the NPP Zvezda K-36 were unintentionally demonstrated at the Fairford Air Show on 24 July 1993 when the pilots of two MiG-29 fighters ejected after a mid-air collision.^[11]

The minimal ejection altitude for ACES II seat in inverted flight is about 140 feet (43 m) above ground level at 150 KIAS, while the Russian counterpart – K-36DM has the minimal ejection altitude from inverted flight of 100 feet (30 m) AGL. When an aircraft is equipped with the NPP Zvezda K-36DM ejection seat and the pilot is wearing the ??-15 protective gear, he is able to eject at airspeeds from 0 to 1,400 kilometres per hour (870 mph) and altitudes of 0 to 25 km (16 mi or about 82,000 ft). The K-36DM ejection seat features drag chutes and a small shield that rises between the pilot's legs to deflect air around the pilot.^[12]

Pilots have successfully ejected from underwater in a handful of instances, after being forced to ditch in water. Documented evidence exists that pilots of the US^[13] and Indian navies have performed this feat.^[14][15]

As of 20 June 2011 – when two Spanish Air Force pilots ejected over San Javier airport – the number of lives saved by Martin-Baker products was 7,402 from 93 air forces.^[16] The company runs a club called the 'Ejection Tie Club' and gives survivors a unique tie and lapel pin.^[17] The total figure for all types of ejection seats is unknown, but may be considerably higher.

Early models of the ejection seat were equipped with only an overhead ejection handle which doubled in function by forcing the pilot to assume the right posture and by having him pull a screen down to protect both his face and oxygen mask from the subsequent air blast. Martin Baker added a secondary handle in the front of the seat to allow ejection even when pilots weren't able to reach upwards because of high g-force. Later (e.g. in Martin Baker's MK9) the top handle was discarded because the lower handle had proven easier to operate and the technology of helmets had advanced to also protect from the air blast