Martin-Baker and the evolution of the aircraft escape systems

The story of the jet age and the Meteor would be not be complete without reference to Martin-Baker, today, they are at the forefront of aircraft safety and still use the Meteor to flight test their ejection seats as they have done since 1946 when Benny Lynch made the first test ejection from Gloster F.Mk III Meteor EE416 on 24 July 1946. The company established in 1929 was led at the time by James Martin (later Sir James Martin) a brilliant self-made engineer and designer, He was approached at the end of the war by the Air Ministry and armed with access to the research carried in Sweden and Germany during the war was quickly able to create a prototype ejection seat that may have saved the life of ... who was killed baling of prototype Meteor F9/40 xxx, being struck by the tail after successfully exiting the cockpit.

The early design required the canopy to be opened and were followed by a normal parachute descent which was opened by the pilot once was free of the aircraft and the seat in which he was ejected to safety. It is not however a simple problem to propel the human body out of an aircraft as its entirely possible to cause serious or fatal injuries if human G tolerance is exceeded or if the pilots limbs are not restrained to prevent them striking the aircraft on the way out or being buffetted by turbulent air once clear of the cockpit.

It became clear near the end of the war that it was not so much the peak G force applied as the rate it was applied and that alignment of the body was critical to avoid spinal injury. These insights led Martin-Baker to develop a two-cartridge ejection gun which provided the peak acceleration combined with restraints and foot rests that helped keep the posture of the ejectee as close to optimum as possible, the seat was activated by pulling down a face-blind (still the preferred method).

To be continued ...


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he earliest prototype Martin-Baker seats were configured with the parachute pack in the seat pan and the water-survival pack & inflatable raft fitted behind the back. This was also the configuration for the earliest production model, the Martin Baker Mk.I seat. This design allowed for increased possibility of acceleration overshoot injuries, as was discovered, and in subsequent Marks, the parachute was moved to a position behind the back, with the water-survival kit stowed in the seat-pan. In subsequent Mark developments, the parachute pack remained in the back stowed position, although with the present generation M-B seats (Mark IX and later), the chute has been moved to the seat’s head-support area.

In September of 1945, development of the prototype Martin-Baker ejection seat had proceeded far enough that a contract was placed for two experimental units which would be flight tested in a high-speed aircraft. The latter turned out to be a Meteor F3, and after a number of dummy ejections and corresponding modifications of such components as the drogue chute and its deployment device (a gun was incorporated in place of a spring deployment mechanism), the first English live ejection test was made by test subject Bernard Lynch on .

It is interesting to note that only 5 days after Bernard Lynch conducted the first successful live test of the Martin-Baker prototype ejection seat in England, a Swedish pilot used the SAAB Type 1 (Type 21) ejection seat in his SAAB J21-A1 pusher-engine aircraft in an actual emergency. Also at this time, the United States Army Air Force was still weighing the merits of ejection seat systems, investigating German wartime developments, and had not even a prototype of its own designed for possible American military aircraft use.

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As early as 1946, the US Navy had determined that England's Martin-Baker Company had satisfactorily pioneered the basic functional principles of pilot egress technology well enough that duplicate or redundant studies by Navy researchers would be both expensive and needless. Thus, the US Navy arranged with Martin-Baker to provide a seat somewhat tailored to US Navy requirements as well as technical support from that company to develop it. Photographs of this first M-B provided US Navy seat show it to be quite similar to that company's 'pre-Mk.I' seat. Along with the actual seat, a 105 foot tall test firing tower was also acquired and a converted Martin B-26 Invader (US Navy JD-1) was specially fitted for planned aerial test firings.

With at least 4 different companies working on US Navy jet aircraft designs in 1946, it was decided to issue an ejection seat specification and allow the individual Navy contractors to develop their own systems, as long as each stayed within specific general parameters. These parameters were based largely on the Martin-Baker seat and the standard features that characterised the English egress philosophy founded by Martin-Baker (face-curtain actuator, drogue gun, etc.) and mandated use of standard US Navy parachutes, survival kits, life-rafts, and other equipment. It is worth noting here that both the first US Navy and US Air Force seats were designed to use seat-type personal parachutes (this is evident in the use of characteristic rounded seat pans in all early US Navy seats), which followed the German example (Heinkel).

Initial US Air Force research showed that the Heinkel ballistic system was not powerful enough to use on anticipated Air Force jet aircraft, as the catapult velocity was insufficient for safe ejection at the new Lockheed P-80's maximum operating speed. However, a fairly simple redesign of the basic Heinkel seat by Wright Field resulted in a prototype US seat, which was tested by a live volunteer from a specially modified P-61B Black Widow on 17 August of 1946. A visual side-by-side comparison of the Heinkel seat and the American seat reveals distinct and clearly identifiable design concept sharing. Progress was made quickly in developing the concept, however, and the straight-winged Republic F-84 Thunderjet became the first production American jet fighter to be equipped with an ejection seat. As mentioned earlier, the USAF approach to ejection seat design called for armrest-actuating triggers (following the German example) which were first raised and then squeezed. Although a conventional seat-type chute was at first used in the original American seat (used in the P-80), a back-type parachute was later incorporated; these were not, of course, attached to the seat (similar to the Swedish approach, but contrary to the English design), but were worn by the pilot. Further, all early American seats were not automatic in that man-seat separation had to be achieved manually, and the pilot freed himself from the ejected seat first, then manually deployed his personal back-type chute after physically pushing himself away from the ejected seat. Only later did refinements come to be incorporated into the system, which included leg restraint provisions, correct separation sequencing, fully automatic seat-separations--all or most of these having been addressed or at least recognized as desirable early on by England’s Martin-Baker Company and quite soon thereafter by the US investigators.

Regardless of the rapid pace of American development in design and production of ejection seats for military aircraft, after the war, there was some small amount of resistance to the use of ejection seats on the part of American aircrew, who were somewhat reluctant to fly aircraft equipped with them. More than a few pilots likened the prospect of being seated directly upon a seat's live explosive charge akin to sitting on a powder keg with a short fuse. Purportedly, these anxieties were largely put to rest in 1949 by a series of demonstration ejections carried out by Air Force Captain Mazza from the aft cockpit of a specially modified TF-80C Shooting Star (later standardized as the T-33 jet trainer). The first US Navy emergency use of the new seat occurred later in the same year when the pilot of a McDonnell F2H-1 Banshee was forced to eject at 597 mph over South Carolina. After these events took place, acceptance of the new device was more readily forthcoming among US air crews. In August of 1949 the pilot of an Air Force F-86 Sabre also made a successful emergency escape using the new type seat (North American model T-4E-1 catapult seat), again demonstrating functional performance under adverse conditions.

Again, partly due to the broad approach taken towards development of ejection seat systems among US manufacturers, a number of unusual designs were produced. One in particular, developed for use on the pusher-engined XP-54 Swoose Goose featured a downward-accessed pilot seat, which would lower the aircrewman below the belly of the aircraft so as to clear the arc of the prop. While not strictly an ejection seat, the XP-54 design anticipated several future developments of a downward firing type seat on the Boeing B-47 Stratojet, and the Lockheed F104A Starfighter, as well as the downward firing cockpit system for the experimental XF108 supersonic interceptor (development discontinued after mockups were completed), and the Douglas X-3 Stiletto twin jet research aircraft. At the time, the official emphasis on development of a successful US system was on functional adequacy at high altitude and sustained high speed, as this was the envisioned performance area within which safe aircrew egress would be most critical; the obvious need for safe ejection at lower, slower speeds took a markedly subordinate priority in this overall Air Force conceptual view. Given the notable rate of engine failures and marginal reliability that characterised the early turbojet engines, this misplaced priority would subsequently have substantial consequences as well demonstrated in US Air Force aircrew survival statistics of the period.

Principal among the influences governing the US Air Force decision to continue developing downward ejecting systems was the fact that early catapult inertial acceleration velocities were not completely adequate to ensure clearance of jet aircraft vertical stabiliser assemblies. This, in combination with emergent awareness of the future importance of high altitude interception mission requirements, resulted in a failure to adequately address safety concerns related to 'low & slow' modes of flight performance. Unfortunately, the 'downward egress' concept was somewhat less than favorable for a number of reasons, not the least of them being its unsuitability for the critical low-altitude or zero/zero mode ejection. This fact was later sadly and graphically demonstrated when emergency use of a downward firing Stanley model C-1 seat on a test flight of the Lockheed F104A Starfighter resulted in the death of Captain Ivan Kincheloe in 1958.

As technical advances continued in seat design, it was quite clear that the problem of providing adequate clearance of fast moving aircraft tail structures presented collateral concerns in terms of increased rates of spinal compression injuries related to catapult inertial acceleration forces. Problems associated with having the catapult thrust force located behind the seat center of gravity included high multidirectional G loading due to aerodynamic tumbling forces, wind-flail injuries, wind-blast effects, man-seat separation problems, and parachute entanglements due to aerodynamic instability of the seats after ejection. The problems attending higher inertial acceleration rates to clear the aircraft were obviously not going to be easily solved with continued use of simple explosive pyrotechnic devices. Despite the statistical evidence of only marginal success in achieving safe ejections in the outermost corners of the flight performance envelope, explosively fired catapults of necessity remained in service until roughly 1958, at which time the first rocket catapults were introduced to American ejection seat design (the Convair F102 Delta Dart was the first aircraft fitted with a rocket catapult fired seat, designed by Weber Aircraft Company). [Of interest is the fact that the proof of concept design for the F102--the Convair XF-92A research aircraft--was fitted with an early explosively fired catapult ejection seat originally designed for the Convair XP-81. When the two examples of this combined prop and jet propelled prototype were retired from testing in 1947, this seat was fitted to the XF-92A. Perhaps fortunately, it was never put to 'test' use throughout the duration of that aircraft's flight test program.] Other innovations that were prompted by high rates of spinal injury associated with G-onset forces imposed upon the spine during ejection included the use of variable-density compressible foam in seat cushions, to help reduce or offset accelerative effects on the spinal column. (This same principle is employed today in crash helmet design, for the same end.)

Dr. Robert E. van Patten, former Chief of the Acceleration Effects Branch, Biodynamics and Bioengineering Division of Armstrong Aerospace Medical Research Laboratory (Dayton, Ohio), cites the rapid progress made by the United States in adopting emergency egress systems for its Air Force after the slow initial start at war’s end with reference to the fact that in 1955 the first successful supersonic ejection was made by a pilot from his stricken North American F100A Super Sabre after the aircraft went into an uncontrollable dive. The ejection occurred at Mach 1.05 during a test flight, and while he was injured in the process, pilot George Smith survived the accident and fully recovered. This incident took place less than a decade after the first real investigations into egress systems had begun in America at war’s end. Although the technology was improving rapidly, most US ejection systems were engineered to perform best under 'ideal' emergency situations. However, success in achieving a substantial safety record (and vindication of the new rocket powered catapult systems) is demonstrated by the fact that during the Vietnam conflict (1963 through 1975), more than 25% of the US Navy’s RA-5 (A3J) Vigilante combat ejections took place at speeds greater than Mach 1.0 (the system in use in that aircraft was the North American Aviation produced HS-1 rocket powered seat, with zero/zero to 700 knot IAS capability).

Certainly the Korean War provided much valuable information to the US Air Force and American aerospace manufacturers regarding egress design assessment. Philpott in his book cites the fact that in almost 2000 combat ejections experienced by the US Air Forces during the Korean conflict, 60% of the aircrew ejecting experienced no problems during egress. The other 31% experienced difficulties ranging from seat actuation, canopy release, maintenance failures, incorrect ejection posture, slipstream, through-canopy-ejection, premature seat actuation, and so forth. Similar difficulties, as well as ones unique to carrier operations, were reported by US Navy pilots. Although most of the problems were addressed, Philpott suggests that again the vast number of dissimilar ejection seat designs in use in various aircraft compounded quick resolution. A look at the official US Air Force statistics themselves shows a slightly different picture, with an overall (USAF) aircrew survival rate of 77% during the first 5 years of ejection seat operational experience (1949-1953) . In a recorded 4626 emergency ejections incurred under non-combat conditions, from 1949 through 1980, fatal injuries occurred in 838 (or 18%) of those ejections. With the refinements of automatic release restraint systems, automatic man-seat separators, variably-staged parachute deployment systems, and aerodynamic deployment stabilisation devices such as the DART system, survival rates went up in the 1954-1958 period to 81%. Throughout the period of the mid 50s through mid 60s, most USAF aircraft egress systems received continual updating as operational experience provided new engineering understanding of optimal design features. The overall survival rate thereafter remained roughly at a plateau of about 80% until the 1975-1980 period, in which these values fell somewhat for USAF crews (introduction of the ACES II system, with enhanced ejection safety features).