German 2WK ejection seat developments

 

As is the case with many innovations in technology, it was the Germans who were among the first to explore this area of aviation safety in a serious and innovative manner. Owing to the development of Germany’s covert military capability in the 1930s, much work was being done in aeronautical engineering research for military aviation applications. As Germany explored and researched a new generation of higher performance military aircraft as part of Hitler’s overall build-up of war materiel, the individuals concerned with aviation medicine in the new Luftwaffe recognized a coexistent, renewed need for aircrew safety. This was especially true , since much aeronautical flight testing of new designs was being undertaken, with all the implicit hazards pertaining to that area of technological investigation.

Many ideas occurred to German aeronautical engineers in the process of attempting to address this need for safe egress from crippled aircraft. One of the first was the "boom" concept, in which a pivoted fulcrum, attached to the pilot’s harness and powered by a compressed spring, pulls the pilot free of the cockpit in an emergency. Another of the early ideas was very simple--a compressed spring situated under the pilot’s seat which when released would eject the occupant (assuming that the canopy had been freed and cleared first, not always an easy thing to do using a manual technique and especially in a seriously disabled aircraft).

Interestingly, both these early ideas were also conceived and evaluated by counterparts in England, at the end of the Second World War and without knowledge of the original pre-war German research. In fact, back in 1930 an enterprising RAF Flight Officer, concerned with the increased performance of a new aircraft his squadron was transitioning into, formulated a design for an "escape seat." Consisting of a pilot’s seat mounted on two telescoping tubes, each containing a highly compressed spring, the seat would be pushed with its occupant up into the slipstream of the aircraft when the seat’s catch was released. While the seat was not actually ejected from the aircraft, the idea was that in this position it would be easier for the pilot to roll out of his seat and free himself of the stricken plane. The idea was submitted to the English Air Ministry, along with blueprints and a working model, but no further development was ever undertaken, and thus English innovations in aircrew escape would languish until immediately after the Second World War, when the captured German research and development would stimulate new interest in Allied aircrew escape technology.

In Germany, developments in aeronautical technology were accelerating with the introduction of the jet engine, while by 1939 the Luftwaffe’s Aviation Medicine branch was actively experimenting with ejection systems, using physiological testing devices that included instruments for measuring the forces of gravity and acceleration on the human body. Their tests has determined rough physiological parameters of human ability to withstand G force onset of about +20G for a duration of about 0.1 second. The German preference was at this time for a compressed gas system of ejecting the aircrew seat, although explosive cartridge propelled seats were also under development. The need for adequate aircrew escape from dive-bombing aircraft such as the Ju-87 Stuka, with its sustained high positive G loading during pull-out, significantly motivated investigations into use of high-pressure systems to eject aircrew. The German manufacturer Heinkel maintained chief engineering responsibility for development of all aircraft escape systems, throughout the war, and by late 1942 all German experimental aircraft being flight tested were equipped with some form of Heinkel ejection seat.

With aircraft development feverishly continuing in wartime Germany, Heinkel developed ejection seats finally started being installed in production aircraft, as radical new designs came into use. Although the singular Messerschmitt 262, twin-engined production jet fighter-bomber (Schwalb) did not feature such a schleudersitzaparat (the German term for 'ejection seat', which translates roughly to "seat catapult device") in its earliest permutations, reports suggest that at least a few late versions (Sturmvogel) had what has been described as a catapult-seat (although it is not clear whether the seat was driven by an explosive charge or by a spring mechanism). Other aircraft, such as the Heinkel He-162 Volksjäger, were provided with a compressed air propelled ejection seat. Further aircraft types to feature similar systems included the Dornier Do-335 Pfeil, the Arado Ar-234B Nachtigal, the Heinkel He-177, the Heinkel He-219 Uhu, the Dornier DFS-228, and the rocket-powered Messerschmitt Me-163 Komet (this last system was spring powered). Additionally, earlier research begun in the late 30s by Heinkel had resulted in the first recorded example of a completely ejectable crew compartment being developed. The rocket-powered Heinkel He-176 Natter (the world’s first rocket propelled aircraft) featured a nose section which could be jettisoned in the event of an emergency. Development problems involving successful deployment of the main parachute designed to slow descent of the ejected crew compartment resulted in several innovative engineering designs, and subsequent testing suggested that in the event of the crew being disabled, the He-176’s crew compartment would enable its occupant to survive a landing within the escape pod with only minor injuries.

The Heinkel explosively ejected seat consisted of a seat bucket assembly mounted on 4 rollers which moved in two parallel channels 42 inches long. The charge used in the two tube catapult consisted of 30 grams of powder, firing much like a conventional projectile cartridge, with the two part catapult tube fixed to the upper end of the seat and at the lower end to the aircraft frame. Ejection velocity achieved was 35 fps, with a stroke of 28 inches and an acceleration of about 12 Gs. Although an experimental compressed gas system achieved an ejection velocity of 57 fps and an acceleration of 27 Gs, the system was massively heavy and presented considerable field maintenance problems with over 1700 psig pressures required for successful operation.

On 13 January 1942, the first known emergency use of an ejection seat occurred during a test flight of the Heinkel He-280 jet fighter. The pilot, a man named Schenck, ejected from his iced-up aircraft after jettisoning his canopy, successfully achieving safe egress from the machine. Although Schenck’s was the first known use of an ejection seat for emergency egress, the Heinkel compressed air driven seat used by Schenck was purportedly tested in an experimental ejection from a test aircraft by a Heinkel employee named Busch, prior to Schenck’s 1942 ejection. (These facts was unknown outside of Germany until after the end of the Second World War, and for a while it was thought that the first successful emergency ejection was made by a Swedish pilot from his crippled SAAB J21-A1 aircraft--with "pusher" type propeller powerplant--on 29 July 1946).

By the end of the Second World War, more than 60 emergency ejections had been made by Luftwaffe personnel, and German Aviation Medicine branch research in aircrew egress technology had progressed substantially into areas of high-performance aircraft escape systems at proportionately high physiological limits of human endurance. Among the important facts that had become clear to German researchers, however, was that compressed gas driven systems were prohibitively heavy, requiring installation of heavy system components to contain the gas under high enough pressure to perform as required; they were furthermore quite difficult to maintain and keep operational under actual battlefield conditions. Ballistic (explosive) systems were lighter, but the requisite technology, while promising, was still in its infancy. These facts were not lost on American or British scientists going over the captured German research at war's end.