The Ejection Seat That Thinks For Itself

That is why Martin-Baker Aircraft Company, near London, the pioneer ejection seat manufacturer, is now devising systems that can ‘thing for and decide precisely when the moment has come for a pilot, or navigator, to eject. The company believes that technology has reached the point now where automatic ejection using an ‘intelligent’ seat is feasible. But it will probably be ten to fifteen years or more before it is in general use.

Part of the reason is that such a seat needs to be developed in parallel with progressive design work on new aircraft and partly because aircrew tend to be justifiably wary and conservative in their views about radical changes which will affect flight safety.

The basis of the system would be a seat mounted computer which would ‘talk’ constantly to the aircraft’s primary computer. It would be kept up to date on the aircraft’s speed, height and attitude and would take over operation of the seat ejection mechanism if the main computer sensed catastrophe and commanded instant ejection. The possibility of using very advanced technology and electronics opens up a whole new area for ejection seat development, which is now being researched.

It is feasible that an aircraft’s main computer could assess a situation and judge the risks of ejecting a pilot at certain speeds. For instance, if an aircraft were about to crash in a very short time, its main computer would decide to eject the pilot and instruct the seat computer to operate to the maximum physiological limits of the human frame.

At present, seats are propelled by a fixed thrust gun and rocket system. The angle of the rocket motor exhaust is also fixed. But it might be possible to develop a variable thrust gun and rocket that would adjust itself.

Altering the trajectory of the seat has been looked at before in the United States, in a programme known as the ‘maximum perform1=1nce ejection seat’ which provided the upward seeking seat. The method was not adopted, however, because it would probably be helpful in only a minority of emergencies and could have degraded the performance of the seat in its normal mode. Developing electronic controls could now change that picture.

With the arrival into military service of the new version of the Harrier jump jet, the GR5, a new seat will be fitted by MartinBaker which will have pitot tubes to sense airspeed. In a very high-speed ejection it is better, if possible, to delay the parachute opening, to reduce the shock-loading effect on the aircrewman’s body. At lower speeds, the sooner the parachute is opened the better.

The next step will be a seat, now under development by Martin Baker, called the Mk14. The company has won, after tough commercial competition, the United States Navy Aircrew Common Ejection Seat (NACES) contract. The aim is to develop a new common escape system for a whole range of aircraft including the F-18, A-6, EA-SB, F-14O and the T-45 trainer.

NACES will be the baseline for all new United States Navy aircraft and has been designed with growth potential, which means that it can be updated as technology becomes available, without drastic design changes to the interface of the seat with the aircraft or the seat with the crewman.

Martin-Baker hopes that a version of this seat will be chosen for the new European Fighter Aircraft (EFA) and the production version of the French Rafale due to enter service in the mid-1990s.

Between this seat and fully automatic systems may come versions that will be able to warn a pilot via the aircraft’s main computer that ejection is rapidly becoming imperative. A flashing light on the instrµment panel will say “Eject!” – once it glows steadily the pilot will not need to think about the situation, but just to pull the ejection seat handle and rocket to safety.

As well as reducing the workload for aircrew, fully automatic seats will overcome the psychological problem that the pilot has in deciding to leave an aeroplane that may be worth anything up to $25 million, as in the case of the latest versions of the Tornado, Tomcat and Eagle.

The pilot may not want to go because of the value of the aircraft; because he believes he is good enough to save the day even in the case of a cc;ltastrophic mechanical failure; or even because he refuses to admit to himself that he has made an error which will destroy the aircraft. But very often the one thing he cannot afford to do is to spend time considering the problem. In the future it is most likely that the decision will be out of his hands.

Although Martin-Baker is spending a great deal of time solving the particular problems of high speed military flyers, the company has developed a whole range of seats for installation in particular types of aircraft, which it is constantly improving.

With turboprop military trainers nowadays able to reach speeds of over 330kts and often flying at heights of under 300m, Martin-Baker decided to develop an ultralight escape system known as the Mk11.

It embodies all the design features of the company’s more sophisticated systems, but at a reduced weight and size. Martin Baker state that it has been ordered for the Swiss Pilatus PC-9 trainer on order for the RAAF.

Another safety seat application is for helicopters. Not an ejection seat this time, but an armoured crashworthy seat designed to absorb energy in the event of a crash. The seat has already been selected for the A. 129 Mangusta anti-tank helicopter and may be fitted to other European machines including the new Westland Agusta EH 101.

The energy absorption device utilises the principle of forcing soft steel rods through a number of fixed dies. The seat is of a wraparound design to give ballistic protection. The seat bµcket is made of Kevlar and ceramic. Laminate which is up to 50% lighter than a comparable steel product for the same given ballistic performance.