MARTIN BAKER AIRCRAFT

 

Martin Baker Mk1 Ejection Seat

The Mark 1 seat was the first seat qualified for installation on aircraft. It used a single stage design with a two cartridge 60 foot per second catapult. The seat was stabilized in descent by a two foot diameter drogue chute, which was deployed by a 24 foot static line with the occupant manually releasing the harness and deploying his parachute manually. The first successful test of this seat was carried out by Bernard Lynch on 24th July 1946, who ejected from a modified Meteor at 320mph IAS at 8000 feet.

Mr Lynch went on to carry out over 30 live test ejections.

The first successful ejection made in the USA was by Lieutenant Furtek, USN on 1st November 1946 at Lake Hurst.

The seat was installed in the Meteor, Attacker, Wyvern, Canberra, Sea Hawk, and Venom.

A considerable number of successful ejections were made using the Mk 1 seat.

This Mark of seat of course was a First Generation Seat for obvious reasons.

Martin Baker Mk2 Ejection Seat

Further testing and ejection experience had shown a number of problems with the Mark 1 seat. The first was the need for manual release of the occupant. If the occupant was injured or unconscious then he would be unable to release the seat harness.  The second was the difficulty in judging correct height for parachute deployment. These were dealt with in the Mark 2 by the inclusion of a clockwork timer that activated upon ejection. At the end of five seconds, the drogue chute was disconnected from the seat by the use of a scissor shackle. As it pulled away, it was connected to an apron like static line which tipped the seat occupant forward and it caused the main parachute to be deployed. The operation of the timer was inhibited by an aneroid capsule which blocked the running of the clockwork release. On reaching a pre determined height (usually 10,000 feet asl) the clockwork mechanism was allowed to run freely, allow the scissor shackle to operate and in turn allow the drogue to separate from the seat pulling out the pilots main ‘chute. Early Mark 1 seats were retrofitted to the Mark 2 standard as well as new seats constructed to this specification.

Martin Baker Mk3 Ejection Seat

The Mk 2 seat had obviously increased the chances for a safe ejection, and were to all intents and purposes adequate for the aircraft of the day. However, the chances of escaping at slow speed and low altitude or fast speed and high altitude were areas of the “envelope” which needed expanding. Higher performance aircraft such as the all weather Javelin  and the V bomber force were being introduced into service. These needed a higher trajectory ejection to clear the tail. An increase in trajectory would also give an advantage for very low altitude ejections. The Mark 3 seat brought in some much needed increases in performance.

The simplest way of increasing the trajectory height would have been to increase the explosive charge in the ejection gun, hut enough has already been said to show that this would have increased the peak acceleration and onset of 'g' to an unacceptably high limit, well beyond the limits of human toleration. To avoid this harmful effect while still achieving a higher ejection trajectory, an ejection gun with a stroke of 72'', giving a velocity of 80 ft/sec., was designed to replace the existing 60 ft/sec. gun. While maintaining the characteristic low peak acceleration and rate of rise of 'g' of the earlier gun, this provided the extra velocity necessary for increasing the trajectory height.

The gun consisted of three tubes, two of which telescoped inside the main outer tube, powered by one primary and four auxiliary charges, the latter being arranged in two pairs. When the primary charge was fired an inner tube was unlocked by the generated pressure and began to rise, together with the intermediate tube, carrying the seat and occupant occupant with it. After extending 6'' the lower two auxiliary cartridge ports were uncovered, allowing the flame to ignite the first pair of cartridges, and a further extension of 9½ '' uncovered and fired the second pair of auxiliary cartridges. The gun continued to extend until the intermediate tube was arrested by a flange on the outer tube, the shock being cushioned by fifteen hollow gas-filled rings. The inner tube continued extending on until it broke away from the gun, carrying the seat and occupant clear of the aircraft.

Although this gun was designed primarily to give a trajectory adequate to clear the higher fins of the new aircraft, it was found, during tests, to possess the added advantage of gaining trajectory height at low speeds. Trajectory heights of the order of 90 feet above aircraft datum are obtained with this gun at moderate air speeds and this enhances the chances of safe escape near the ground. In practice the use of the seat is limited to a minimum speed of 90 knots at ground level.

During ejection at very high speeds it was found that the thigh guards of the Mk 1 and 2 seats were not completely effective in the prevent ion of leg flailing. At these speeds the airstream could be sufficiently powerful to lift the feet from the footrests and carry the legs over the top of the thigh guards, where severe injury could possibly he caused to the knee and hip joints. It therefore became imperative that some form of mechanical leg restraint should be introduced on the seats used in the faster aircraft. A number of different methods were investigated including guards which folded inboard over the thighs, but were discarded for a system securing the legs to the seat by nylon cords, subsequently introduced on all Mk 3 type seats. The arrangement consisted of two reinforced nylon cords, each connected to the cockpit floor by shear pins designed to pull away at the load required to ensure that the legs were held back against the forward edge of the seat pan. The other end of each cord was passed through snubbing units fixed to the forward face of the seat pan and then through metal rings on webbing garters strapped in the occupant’s legs. The two free ends of the cords were then connected to the harness release box.

The cords were arranged to allow the movement of the legs whilst seated in the cockpit, but, on ejection, tightened up between the snubbing units and the harness release box before breaking away from the floor thereby automatically securing the occupants legs to the front of the seat pan, where they were firmly held until the harness was released and the occupant separated from the seat .

As already stated, the introduction of 80 ft per second ejection gun resulted in a gain of trajectory height at low altitude. In order to take full advantage of this and further enhance the chances of safe escape near the ground, consideration was then given to the practicability of speeding up separation from the seat after ejection.

The drogue of 24 in. diameter, then in use, streamed the main parachute 5 sec. after ejection, but it was obvious that a drogue parachute of constant canopy size would only achieve efficiency at a certain combination of speed and altitude. The time interval, with this particular drogue, was selected to allow the speed to drop from the highest probable ejection speed to one safe for opening the main parachute, and in other conditions its performance was less efficient. Intensive development work and flight testing with various types of drogues led to the introduction of the Duplex Drogue system. This scheme employed two stabilizing drogues in tandem, a small drogue of 22 inches diameter, known as the controller drogue, and a larger main drogue of 5 feet diameter. The controller drogue was automatically extracted by the drogue gun on ejecting, and, when deployed, brought the seat back into a horizontal attitude, then towed the main drogue out of its container. The main drogue streamed the parachute when separation occurred, and this, when developed, tilted the occupant clear of the seat. The action of the controller drogue was twofold first, to get the seat into a horizontal attitude so that the subsequent deceleration on the seat and occupant was linear and consequently more tolerable; second, the most important, it prevented explosive opening of the main drogue. In tests, when a 5 ft. diameter drogue was deployed without a controller at 600 m.p.h. and at a height of 150 ft. it was torn to shreds, the drogue producing such violent loads that the face screen was torn and the seat harness broken. With the controller drogue employed under similar conditions none of the components showed any signs of distress. Similarly, the main drogue prevented the explosive opening of the parachute, thus opening shocks and decelerations were reduced to within the strength limitations of the parachute and the physical limitations the body.

With the incorporation of the Duplex Drogue it was found to be practicable to reduce the time delay between ejection and the streaming of the main parachute from 5 sec. to 3 sec. At the same time the delay in the firing of the drogue gun was reduced from 1 sec. to ½ sec. These improvements were introduced, together with the 80 ft. sec. gun and leg restraint gear, on the Mk. 3 ejection seat , a great step forward from the older Mk.1 and the first automatic seat, the Mk 2.

A series of fatal accidents involving aircraft of the Navy and Royal Air Force during take-off and the resultant ejections at too low an altitude impressed the need for an ejection seat with ground level capabilities. The fact that the Mk. 3 seat was able to operate successfully from low altitudes was fundamentally due to the method and speed by which the Duplex Drogues deployed the main parachute and, the higher seat trajectory imparted by the 80 ft. per sec. ejection gun. With ground level ejections, however, every second between the firing of the seat cartridge and the deployment of the main parachute is vital, and consideration was given to the reduction of the 3 sec. delay in the time-release mechanism. A delay of 1 ½ seconds was ultimately selected as being the most suitable to ensure deployment of the parachute at the top of the trajectory. With. this 1 ½ second delay fitted to a standard Mk. 3 seat, Squadron Leader John Fifield, O.B.E., D.F.C., A.F.C., ejected from the Mk. 7 Meteor, taking off at Chalgrove on 3rd September 1955, the culmination of a long series of dummy runway ejections. Squadron Leader Fifield was safely on the ground six seconds after firing himself out of the Meteor, thus converting the sceptics who were previously convinced that a man would not survive such an ejection. The following month, again in a standard Mk. 3 seat, Squadron Leader Fifield made a test ejection from a height of 40,000 feet.

Experience in service had shown that vital time was being used to operate canopy jettison gear and carrying out other pre­ ejection drills. Under certain aerodynamic conditions, or if damage had occurred, it was possible that the canopy might not leave the aircraft cleanly, even though it had been unlocked. This could give rise to the ejected seat colliding with the canopy and becoming entangled with it. Under high speed conditions difficulty was also encountered is grasping the face blind firing handle, due to the slipstream entering the cockpit and causing severe buffeting once the protecting canopy had left the aircraft. By providing au explosive canopy jettison system powerful enough to force the canopy clear under all conditions, and by linking its operation to the ejection seat firing handle, it was possible to overcome these difficulties, the ejection position being adopted prior to the canopy leaving the aircraft.

The canopy jettison equipment consisted of a unit bolted to the rear of the ejection seat guide rail and containing a canopy jettison breech, together with a one second delay mechanism, On pulling the ejection seat firing handle the sear of the canopy jettison gun was withdrawn, the cartridge detonated and the gases passed through piping to the two canopy jettison jacks. The expanding gases forced the pistons of the jacks upward, first operating the canopy locks and then raising the canopy for the airstream to carry it clear of the aircraft. At the same time as the firing of the canopy jettison cartridge the time-delay mechanism was tripped. This ran for one second, at the end of which the main ejection gun was fired, thus allowing the canopy to be well clear of the aircraft structure before the seat and occupant were ejected. The adoption of this system in Hunter, Javelin and other aircraft meant that one second after the pilot initiated the ejection procedure be would be carried clear of the aircraft, no time being wasted on any other pre-ejection action which may have prejudiced his chances of escape.

Martin Baker Mk4 Ejection Seat

With the advent of a new type of aircraft known as the “light fighter” it became increasingly important to reduce the weight of the ejection seat. At the same time it was essential that the reduction in weight should not impair the operation and efficiency of the seat in any way. The construction of the Mk. 4 seat although retaining the essential components of its predecessors, was therefore considerably modified.

The basic 80 feet per second ejection gun was retained, having been proved to be sufficient for all current requirements, as was the Duplex drogue system deployed by the half second time delay drogue gun, together with a 1 ½ second time-release unit. The conventional type of guide rail was eliminated and superseded by channel members mounted on the sides of the ejection gun. Steel slipper pads mounted on the seat beams located the seat in position in the channels and guided it out of the aircraft on ejection. The seat structure consisted of a framework of two side beams bridged by three cross members, this framework supporting the seat pan and the drogue container: the drogue gun and the time-release unit being mounted on the side beams. The top cross beam took the full thrust of the ejection gun and contained the seat latch mechanism for locking the seat to the ejection gun. The centre cross member served as the attachment point for the shoulder harness whilst the lower member provided an anchorage for the seat height adjusting mechanism. Although fitted primarily with the face screen firing control, an alternative firing handle was fitted in the leading face of the seat pan. This enabled the occupant to eject when conditions of ‘g’ precluded the use of the face screen handles.

The comfort of the seat was considerably improved by the design of the parachute pack and dinghy pack alongside that of the seat, instead of trying to use the existing safety equipment. The parachute pack was a back-type, horseshoe in shape, and mounted high on the back of the seat in the best position for automatic deployment together with a high degree of comfort. The parachute harness was redesigned to combine with it the safety harness all in one, with only one quick-release fitting which was fastened by the occupant when strapping in the seat, and remained fastened throughout any subsequent ejection until released by the occupant at the conclusion of the parachute descent. Thus combined harness was attached to the seat by two locks in the rear of the seat pan and another lock in the back oh the seat at shoulder height. The locks being released by a redesigned time-release unit at the correct instant after ejection, through a linkage system installed in the seat. The locks could also be operated manually in the event of failure of the time-release unit by a manual separation lever on the seat. This arrangement of the parachute and harness was also fitted to some of the later Mk. 3 seats. Later Mk. 4 seats were fitted with a snubbing in the top lock and release lever which permitted the occupant to lean in the seat but ensured that he was held firmly in the event of an ejection or a crash landing. A number of variations of survival pack were designed by Martin-Baker according to the various requirements of the Air force concerned, but all embodied the principle of seat cushion and container for dinghy and survival equipment. The seat cushion was designed to give maximum comfort and filled with resilient padding slow to return to its original form after compression, hereby helping to absorb the acceleration forces imposed during ejection.

These Mk. 4 seats have been fitted to some 35 different types of aircraft, the first emergency ejection being from a Fiat  G 91 in March 1957.

The Mk 4 series is generally considered to be the first Second Generation seat

G SWITCH

The time delay required for safe election at ground level had been found to be 1½ seconds, but this was only the case if ejection took place at low speeds. At high speeds this period of delay was insufficient to permit the seat to decelerate to a speed at which it was safe to deploy the main Parachute. Ideally, a unit was required which would incorporate a delay varying in accordance with the speed at the time of ejection, and some means was therefore sought it combining both the 3 second and the 1½ second and delays in the same unit. The result was automatic selector known as a ‘g’ switch, which was adapted to fit the 1½ second time delay unit.

The ‘g’ switch consisted of a small weight, free to oscillate within the Time Release Unit. When the drogues deploy, the seat assumes a horizontal attitude and the retarding force imparted by the drogues cause the weight to pivot forward, engage the starwheel of the escapement and prevent the unit from running out. As the seat is decelerated, the retarding force decreases and a light spring returns the weight to its original position allowing the unit to run out.

When an ejection takes place at low speed, the time delay unit runs unimpeded (providing the ejection is below 10,000 feet and not subject to barostatic control), allowing the drogues to he released 1 ½ seconds later, but, in the case of ejection at high speed, the 'g' switch is engaged and the correct delay is auto­matically selected by the particular deceleration loads imposed. With the introduction of the g switch it was therefore possible to provide for safe ejections at all speeds likely to be encountered any modern aircraft. At a later date the delay was further reduced by ½  second and the 1 ¼ second time-delay became standard equipment on the majority of Martin-Baker seats.

GUILLOTINE SYSTEM

In order to reduce the number of operations necessary when making a manual separation after ejection, a guillotine system of disconnecting the parachute withdrawal line from the drogue was introduced. A small guillotine unit was mounted, usually on the side of the drogue container, with the parachute withdrawal line positioned in a spring loaded guard immediately above the cutter of the guillotine. The cutter was operated by a cartridge, fired by a short static cable between the hack of the parachute case and the sear of the guillotine firing unit. As the seat occupant moved forward on separation, taking his parachute pack with him, the cable removed the sear to fire the guillotine and cut the with­drawal line.

This arrangement rendered unnecessary the need for and operation of two D rings on the parachute harness. In the event of failure of the time-release unit all that was now necessary was for the occupant to operate the harness release lever on the seat and pull his rip cord D ring to deploy the parachute.

An alternative method of firing the guillotine was later introduced which interconnected the firing of the guillotine with the operation of the manual separation handle instead of using a static cable attached to the parachute pack.

Further modifications have been made to a number of the Mk. 4 seats, including the adoption of leg restraint lugs which plug into latch boxes on the front of the seat pan instead of being secured to the harness release locks at the rear. The 1 second time-delay mechanism after the canopy jettison equipment has been initiated is now available contained in the breech of the main ejection gun, whilst the canopy locks can now be operated by the expanding gases of the canopy jettison charge via a by-pass valve instead of the initial movement of the jacks.

Martin Baker Mk5 Ejection Seat

The United States Navy required a more substantial seat than the Mark 4 for its aircraft. The intrinsically more violent life aboard an aircraft carrier with catapult launches and arrested landings placed more stress on the airframe. Therefore the seat needed strengthening to provide safety for the occupant. The seat and harness were strengthened to withstand deceleration loads of 40g instead of the 25g British specification. The seats were also fitted with canopy breaker lugs on top of the drogue box to facilitate ejecting through the canopy. Due to the success of the Mk. 5 seats it was decided to standardise the fitting of Martin Baker seats in all US Navy aircraft. A policy which has been continued to this day.

Martin Baker Mk6 & Mk7 Ejection Seats  

The seats prior to the Mark 6 provided adequate response when the aircraft had either airspeed or altitude. The manufacturer and users saw the need to extend the operating envelope to include zero airspeed and zero altitude performance. The existing 80 ft/second gun provided enough force for ejection without being excessive in force or G onset. A more powerful gun would overstress the occupant and potentially result in injury. For that reason a series of rocket tubes were attached to the bottom of the seat . They were initiated by either a static line attached to the aircraft or hot gas from the catapult. Addition of the rocket assembly to the basic designs converted the Mark 4 to Mark 6 and the Mark 5 to Mark 7 standard. The Mark 7 seat was further modified as other improvements were added such as power retraction which pulled aircrew into a suitable posture for ejection, a remotely fired rocket and sequencing system which did away with the vulnerable static line firing system, and other subtle refinements which made the "seven" probably the most advanced mechanical seat of its time. Many thousands were made and were fitted to aircraft such as the Phantom, Tomcat, Crusader and many others.

As mentioned the "rocket seat" gave a full Zero / Zero capability; safe ejection from a static aircraft. The addition of a rocket pack fired the ejectee to a height of about 350 feet. Enough for the drogues to pull out and deploy the personal parachute.

"Doddy" Hay gives an excellent description of testing these seats in his book, "Man in the Hot Seat".

Another advantage of rocket assisted seats is that they perform so much better than the 'gun only' system in aircraft experiencing high sink rate in the horizontal plane. This is a major problem with V/STOL aircraft who experience engine failure in the hover.

In some systems used by other manufacturers, the rocket motor is incorporated in the ejection gun. This however cannot give the thrust angle needed to give altitude if the ejectee "bangs out" in a horizontal attitude, i.e. aircraft is nose down. The 2"rocket pack fitted to the Mk 9 seats in the Harrier have a full eject capability in sink rates as high as 80' per second.

The angle of the thrust provided by the rocket pack can be altered by a pitch control unit attached to the side of the seat pan. The pilot dials in his dressed weight through a control knob until his weight is shown in a small window on the unit on entering the cockpit and this in turn (through a screw jack) alters the angle of the rocket pack to ensure that the trust component is directed through the centre of gravity of the mass should it be ejected. This in turn gives the best altitude to the pilot when needed.

The "7" is probably the pinnacle of purely mechanical seats. Ballistic operation started to show on some systems, but the operation of all major components utilises mechanical workings first seen on Mk 4 seats.

more to come

Martin Baker Mk8 Ejection Seat

The Mk8 seat was a part of the design process for the T.S.R.2 aircraft. With cancellation of the aircraft project, the need for a seat specific to that design was no longer present. Since it had been designed without the restraint of retrofitting an existing airframe, the designers had had a free hand in the development process. The seat was undoubtedly the most advanced aircrew escape system produced to that date. Not only did it look different from previous seats, it included new systems which are still designed into current seats.  This produced some innovations that were incorporated into later seat designs. One of the more obvious is the incorporation of the main parachute in the head rest, this being the first Martin Baker seat to use this system. The drogue gun was incorporated into the top of the left hand guide tube and the Barostatic Time Release incorporated into the top of the right hand side guide tube, the standard beam mounting system was not used. The only firing handle was between the pilots knees, tests having shown that this handle was quicker to operate in all flight modes than a face blind option. Modern helmets and visors had made the need for face protection obsolete.

This mark of seat was not fitted to any other type of aircraft.

There were approximately only a maximum of some 60 of these seats made (including development models) and therefore it would be fair to say that this mark is one of the rarest seats and therefore is a highly desired collectors item. Some would say that this is one of the most aesthetically pleasing seats to look at. There are some (dare I say it) good photos of an "8" on the photos page showing these innovations.

The Mark 8 series seats are generally considered to be the first Third generation Seats.

more to come

Martin Baker Mk9 Ejection Seat

Early versions of Martin-Baker seats represented an evolutionary path and by the early 1970's had been in production for over 23 years. The timing for the components and processes was provided by a combination of clockwork and barostatic mechanisms. The drogue gun, barostatic time release mechanism, Ejection gun, guide rails, leg restraints, PEC and duplex drogue system were retained. (why change a winning combination), but major changes were made to the seat structure, drogue container, parachute and seat pan. These changes made great improvements in comfort and appearance.

This was the first seat to incorporate a detachable seat pan which removed the necessity of removing the whole seat from the aircraft for routine maintenance.

The parachute pack was moved back to the rear of the seat. This in hindsight was not an improvement over the "8" and was moved back to the headrest in later seats.

 The Mk9 was the first seat to remove the firing cable combinations and replace them with gas operated (ballistic) devices. All sears and retraction systems were powered by gas from a cartridge (s) initiated by the seat pan handle.

The "9" is fitted to Harrier and Jaguar aircraft in RAF use as well as many others in use throughout the world.

more to come

Martin Baker Mk10 Ejection Seat

The "10" seems to be a culmination of all the best points of other seats. Considerable design changes have also taken place to reduce the time lapse between initiation of the ejection and being under a fully deployed parachute.

The main changes include:

The "10" is currently fitted to BAE Hawk, Tornado, Mig 19 (Pakistan) CASA 101, Sea Harrier, Macchi 339, MD F18 and 40 other aircraft types.

more to come

Martin Baker Mk 11 Ejection Seat

An ultra lightweight (90 lb / 40Kg) seat primarily used in training turboprop aircraft.

more to come

Martin Baker Mk 12 Ejection Seat

Basically the "12" is a more sophisticated Mk 10 L but has the capability to sense airspeed  and adjusting the mode of operation to suit the circumstances. The "12" can be retrofitted to aircraft fitted with "10"'s without modification to the airframe.

The pitot heads are mechanically deployed on ejection and sample the airspeed to provide data to an onboard sequencer which then decide on one of three modes of operation:

  1. Low speed / Low level

  2. High speed / Low level

  3. Any speed / High level

The speed sensing system is biased towards the high speed mode. If any one of the three speed sensing systems "vote" for the high speed mode then the sequencer will opt for that mode.  If no data is received from the sensing system the seat will failsafe to high speed mode. This ensures safe deployment of the main chute. The drogue is deployed by a tractor rocket system and not a gun as in previous systems.

The seat is fitted with the new Irvin AIM (Auto inflation modulation) bi porosity conical parachute.

The rocket motor delivers equal thrust and a small burn (.5 sec) lateral thrust motor has been fitted where divergent trajectories are required as in multiple placement situations.

Martin Baker Mk 13 Ejection Seat

Ok, so there wasn't one for obvious reasons.

Martin Baker Mk 14 Ejection Seat

In 1983, Martin Baker reviewed its relationship with the US Navy when it was awarded the contract to continue supplying this valued customer. The seat developed was the Mk 14US now called the NACES (Naval Aircrew Common Ejector Seat) and was initially fitted to Tomcat F14D, F/A18 Hornet, T45 Goshawk and A6 Intruder (later Dropped). Some 500 seats had been delivered by September 1993 and 71 lives saved.

To learn more about the NACES, smurf over to: NACES

more to come

Martin Baker Mk 15 Ejection Seat

An advanced lightweight seat used in training turbo prop aircraft.

more to come

Martin Baker Mk 16 Ejection Seat

Currently under development for use in the Eurofighter Typhoon. Much technical information is still highly classified and photos are rare.

The main points of interest are:

The "16" is cleared for service in the Joint Strike Fighter, Typhoon, Raphael, Texan II, NASA T38 and others.

The Mark 16 series seats are examples of the Forth Generation of seats.

more to come

Martin Baker Mk 17 Ejection Seat ??

The following notes are the thoughts of the author and are not attributable to other sources.

If you read the whole of the above page you will see that the development of Martin Baker seats follow a clearly defined evolutionary path and in my opinion the Mark 17 seat may show some of the following logical progressions:

 

more to come...lets see if I'm right?

 

last updated JANUARY 2003