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Aviation History
1950
1950 - 1011.PDF
25 May 1950 645 When the crew of the Skyknight decide to "abandon ship," the pilot pulls a toggle and releases the seat-backs so that they can be swung into the corners of the cockpit, thereby permitting the seat-pans to be slid outboard and aft; at the same time, the chute entrance and exit doors open, exposing the escape tunnel. By means of a hori- zontal "vaulting-bar" across the top of the cockpit door, the escaping crew hoist themselves down the chute feet- forward into the breeze. Escape in water is possible through a ditching hatch in the cockpit canopy. The chute, incidentally, also serves as the normal means of entering the aircraft. A considerable number of test drops with both live and dummy subjects have been made via the belly hatch of the Skyknight. (See page 785 of the December 22nd, 1949, issue of Flight for an illustrated sequence of one of these ejections.) Experienced parachutists have made 22 successful bale-outs at speeds from 140 to 440 m.p.h., while further tests with dummies were conducted up to nearly 500 m.p.h. The aircraft was put through tight turns and pull-outs to learn if a pilot could get into the slide-chute against the corresponding g forces, the results indicating no difficulty up to a limit of about 3J g. In order to cut down the opening shock of the parachute canopy at the higher speeds, the parachutists delayed open- ing their chutes from 5 to 20 sec. As air speeds were increased beyond 300 m.p.h., some helmets were lost and several flying suits were torn on entry into the airstream ; also, the jumpers tended to "jack-knife" somewhat, but no personal injuries were received, nor were there any un- comfortable experiences recorded. Furthermore, although at the higher speeds the exit trajectory became progres- sively closer to the fuselage, the subjects consistently fell clear without contact with the jet-stream. Douglas Nose Capsule.—For safe egress in the upper ranges of the speed-altitude zone, Douglas, in co-operation with the U.S. Navy and the N.A.C.A., have devoted a lot of engineering thought and laboratory testing to the self- contained escape capsule which relies upon jettisoning the ® entire nose section of the fuselage, complete with pilot and seat in situ. In this novel scheme the nose capsule is designed to fall freely away from the rest of the aircraft structure, after which the pilot can bale out when the capsule has slowed down. By virtue of their long-range supersonic research programme, Douglas are probably ahead of the rest of the field in this particular design art. Some of the alternative partitioning schemes and deceleration devices investigated by Douglas engineers are worth portraying—if only to serve as stop-signs or caution- signals for others. It will be noted from the sketches in Fig. 5 that the idea was canvassed of leaving the pilot and seat temporarily attached to the rear part of the structure until the nose section -had fallen clear. Needless to say, this rather terrifying proposal was quickly discarded because of possible collision of the two parts and the difficulty of making a clean break-away from the un- balanced airframe after loss of the nose section. (At this preliminary stage no one seems to have worried unduly about the hapless pilot sitting out in the breeze like a monkey on a stick!) On deciding in favour of the nose section as the logical place for the escape capsule various deceleration devices such as parachute or dive brakes were considered. Both these ideas, however, were abandoned, since further analysis indicated that the nose capsule would probably slow down to about 300 m.p.h. by itself, after which it is considered practicable for the pilot to bale out, the nose portion affording sufficient protection for a safe egress. The remaining problem resolved itself into the best method of partition at the fuselage, disconnection joints. After consideration of both explosive and mechanical severance, the latter plan was adopted as being the most reliable from a positive-control standpoint. Incidentally, this gives the writer a chance to correct his own statement (made when describing this Douglas Skyrocket feature in the January 5th issue) to the effect that the severance mechanism was explosive. The mechanism finally chosen comprises four bomb-rack- Fig. 5. Douglas nose capsule : Above are sketched five schemes which were turned down as (I) pilot-ejection too dangerous, too complicated, speed retarded, (3) parachutes not practicable, difficult to control explosive charge, (5) pilot's backrest on lage—too dangerous. The drawings on the left show the operational sequence of the scheme finally adopted on the Skyrocket research aircraft. wnicn (2) too <«> <Mfuselag type release hooks designed to operate mechanically by a pull-handle located above the centre of the instrument panel. A 6o-lb pull on the handle completes, successively, a two-second decompression of the pressurized cockpit and release of the-disconnection hooks. Once clear of the air- craft, and with the falling speed sufficiently reduced for safe exit, the pilot bales out of the nose capsule by pulling another cable handle located close to his right hip, a 10-lb pull simultaneously releasing his back-rest and shoulder- harness fastenings and allowing him to fall clear from the rear of the cockpit. It might be mentioned at this point that the cockpit canopy can also be jettisoned in the customary manner for low-speed exit; which, perhaps, is more in the nature of a token offering rather than a practical escape route, seeing fhat present-day sartorial encumbrances make flying a
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