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Aviation History
1956
1956 - 1646.PDF
Consecutive ejection of two dummies from a sled-mounted Convair TF-102A cockpit at 240 m.p.h. At left, the M3 telescopic gun has thrown its seat to the arrowed position well below the rocket-assisted RESCU gun's smoke-trail. Above right, the dummies separate from their seats after one second, allowing (lower right) the automatic parachutes to open. The M3 seat is close to the canopy, while the RESCU seat curves right up and away from its dummy. "RESCU" ON this side of the Atlantic, Martin-Baker have successivelydeveloped and demonstrated their automatic ejector seatsin ground-level, low-speed ejection; at speeds up to 420 kt I.A.S. at 1,500ft; and at heights of 40,000ft. Such seats arestandard in all new high-performance Service aircraft. In America the U.S.A.F. is now engaged in developing ejectordevices for the more advanced performance of aircraft now in service or shortly to reach squadrons.' The emergency ejectionlast year by North American test pilot George Smith from an F-100 (at just over Mach 1 at some 6,000ft), showed that, thoughthe seat mechanism worked in those extreme conditions, far more protection was required to shield the pilot from the tremendousforces of airblast and deceleration. Capsules of various kinds have been suggested—one is being developed by Goodyear inAmerica—but the only aircraft known to be so equipped is the Bell X-2 rocket-powered research machine. The first pilot to usethis system was the late Capt. Milburn Apt, when the X-2 went out of control after a high-speed run recently. The recordingcamera mounted behind his shoulder was recovered afterwards and the film showed that he was violently thrown about the cock-pit as the aircraft tumbled from 70,000ft to 45,000ft. Apt pulled the capsule ejection handle; and then for two orthree seconds more the capsule itself must have tumbled until the decelerating parachute opened. Subsequent speed of descentwas calculated as about 128 m.p.h. and the time four minutes. In order to survive, Apt would have had to free himself from thecapsule by jettisoning the canopy, undoing his seat harness and stepping out to make a normal parachute descent. He accom-plished only the first two actions before striking the ground, with fatal results. The standard U.S.A.F. seat-ejection gun at present used inhigh-speed aircraft is a three-tube telescopic, cartridge-operated unit designated M3. Though in itself efficient, it is (perhapspessimistically) reported to be unsuitable for very high-speed ejection; nor is it believed to be more than marginal for the low-speed, ground-level case. Friction in the telescopic tubes under high drag loads, for example, considerably reduces ejection velo-city at high aircraft speeds. Flight of November 9 noted, on page 752, work being carriedout by the Talco Engineering Company on a rocket-assisted ejection gun. Further details have now been released, and theaccompanying pictures show a test ejection of two dummies from a Convair TF-102A cockpit section mounted on a rocket-propelled sled at Edwards A.F.B. One seat had the M3 gun and the other the Talco gun, which is called RESCU—RocketEjection Seat Catapult, Upward. This latter unit uses the standard 4-oz explosive charge to eject from the gun barrel thepiston on which the seat is mounted. Near the top of its travel, the end of the piston is broken open by striking a positive stop,and, as the seat leaves the rails, the hot gases ignite a 5-lb rocket charge housed in the piston. Directed at an angle through the e.g. of the loaded seat, the thrust of the rocket gives an upward force of 5,000 lb and a for- ward force of 4,500 lb, the resultant being 6,700 lb. Upward and forward g loads are respectively 15 g and 13.6 g. The forwardcomponent of the thrust counteracts the violent deceleration forces which mainly prove fatal in high-speed ejections. Longerpropulsion time achieved with the rocket gives greater gain of height, without excessive g, after low-speed ejection. The criticalfactor is the timing of the rocket-charge initiation. Even above 30,000ft, airloads on the pilot during supersonicbale-out may reach seven tons, with deceleration forces of up to 40 g. The safe forward limit is considered to be 35 g, andthe upward (positive g) limit 20 g. Two tests were carried out with the TF-102A cockpit on thesled. First the two seats were shot out at 240 m.p.h. at a Mach number of 0.3. After one second both dummies were releasedfrom their seats and the parachutes began to deploy. The whole sequence lasted five seconds. RESCU had lifted its seat to 124ftwhile the M3 had only reached 55ft. In the second test, made at 590 m.p.h., Mach = 0.73, RESCU achieved 60ft above the levelof the TF-102A's fin-top. The M3 seat was fired shortly after the other in order to assess the effects of the rocket blast onthe remaining dummy. Instrumentation showed that the tempera- ture-rise was not at all dangerous. Both dummies carriedinstruments and telemetering radios. It is claimed that the rocket thrust tends to stabilize the seatafter ejection as well as reducing deceleration forces to a level well within endurance limits. The danger of the extra 5-lbcharge being ignited by enemy action is considered to be small, but there is the problem of the effects of rough handling andageing on the stability of the explosive. Conyair at San Diego has been given a U.S.A.F. contract toco-ordinate all work on ejector seats for Air Research and Development Command. Some 13 companies are involved. Itis hoped to develop a seat suitable for all "century series" fighters and other aircraft such as the SeaMaster and RB-66. A rocket-assisted ejection seat gun similar to RESCU wasdeveloped and patented in 1954 by Mr. David Fulton, who was then working for Reaction Motors, Inc. He is now forming acompany for its production.
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