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Aviation History
1951
1951 - 0919.PDF
576 FLIGHT, II May 1951 CORRESPONDENCE . . . additional cost of giving extra protection to withstand g loadswhich are not a requirement at present. Similarly, as you point out, the reclining-back or sleeperettetype of seat is fitted in some aircraft (though need I add only a relatively few?); but even if there is little advantage in reversingthe direction in which such seats face (which would be hard to prove), this surely is no argument against doing so in the caseof the far more common ordinary type of passenger seats provided. Again, what does it matter what upper limit of acceleration(or, rather, deceleration) passengers can withstand, save from the point of view of possible additional strengthening of seats, whenit is known that survival-rate at any degree of deceleration is superior in the backward-facing seat ? Payload, similarly, is in no way affected, unless operators, intheir mercy, are prepared to sacrifice profits still further to increase the additional protection inherent in merely turning seats roundthe other way. As for evidence of passengers' views in general, I would referyou to a 1947 report, by W/C. Dudgeon, which showed that 80 per cent of passengers on scheduled services questioned in1946 by Transport Command preferred facing backward, 99 per cent thought the view better, and all found bumps and noise lessnoticeable and either felt no more prone or even less prone to airsickness. Similar figures were obtained in a U.S.A.F. survey,also made in 1947, when 94 per cent of passengers favoured backward-facing seatings and 88 per cent wanted all seats reversed.The latter report, incidentally, concluded that the human body can withstand 2Og transversely for brief intervals and that crushinginjuries are 40 times more numerous than fire as the primary cause of death in aircraft crashes.East Twickenham, Middx. VIGILANT. Infallible Glider T READ with great interest, in your issue of March 9th, the note•*• on the performance of the Macrozanonia Macrocarpa seed as an inherently stable glider. The principle was tried as long ago as 1903 by Etrich and Wellsin Austria, with more or less success. They built a man-carrying glider, into which they put an Antoinette engine. It would nottake off, so they built another, the Taube (pigeon), which had a tail and flew fairly well. I built the propeller for the first hop. Then they sold the patent rights to Rumpler in Germany. Thepatents, however, were voided, because one German professor, writing in a magazine, mentioned the use of the principle pre-vious to the building of the Taube. The advanced aeronautical knowledge now available suggeststhat a better d.sign, on this principle, could now be achieved. Chicago, U.S.A. RAOUL J. HOFFMAN. A COMPACT AUTOMATIC OBSERVER IN the flight-testing of aircraft it is usually essential to providean automatic observer to record transient conditions and toprovide photographic or similar records that may be analysed after flight. In design, these observers tend to become bulky andheavy and at times extremely complex. In the larger aircraft, with commodious cabin or bomb-bay space, physical dimensions andweight are comparatively unimportant and the instrument engineer can really spread himself. In the smaller aircraft, the dispositionof the equipment, while still leaving room for the crew and also keeping the weights and the "e.g. king" happy, can provide a realproblem. With this in mind, a small automatic observer has been developedby the instrumentation department of Percival Aircraft, Ltd., for installation in trainer and similar types. With a particular aircraftin mind, it was intended that this unit should be complementary to a human observer: it was not intended to be a fully compre-hensive auto observer. It is, however, capable of a far greater range than were the observers previously in use. It was furtherdesigned for mounting in a small space that was available in the tail of the aircraft, and had to be fitted and removed througha small inspection door. The basic dimensions of the unit are loin high, ioin wide and 15m long. This last dimension can, ifnecessary, be reduced to I2in by fitting a prismatic attachment on the camera lens and turning the camera through 90 deg. The unit,complete with mounting tray, weighs 14 lb. Provision was made for up to 12 Dessyn repeaters (the numberdepending on the dial size), an altimeter, an air-speed indicator, a clock, and message registers for recording fuel consumption andfor numbering the shots. The Dessyn units are direct mounted on to a small sub-panel.The iin diameter Dessyn units are mounted on the back of this panel and the 100-scale division dials are reproduced photo-graphically on the front. This sub-panel is set back from the main panel to bring the plane of the Dessyn dials parallel with the dialsof the normal cased instruments and is made quickly detachable so that changing the instruments presents no difficulties. All theDessyn connections are taken into one Breeze plug and all electrical connections to the observer are made through another. The camera is a Fairchild gun-sight aiming-point camera, fittedwith a Jin reversed telephoto lens in a screw mount. The camera is mounted on an easily removable bracket behind the panel, andphotographs through a mirror mounted opposite the instruments. The camera loads with 50-ft magazines of 16-mm cin£ film, whichgive two minutes' continuous running at the lowest shutter speed of 16 frames per second. This would give too many frames andinsufficient duration for normal work but, by using a simple mechanical time-switch in the control line, it is possible to operateat the equivalent of one frame per second or upwards. Speeds of 48 or 64 frames per second are also available if desired. Illumination is by means of two 30-watt lamps mounted behinda diffuser in a ventilated lamp-house on the hinged lid covering the dial side of the panel. A reflector is mounted in the bottom of theunit to look after the lower half of the panel. Using Ilford HP3 negative film, this lighting is adequate even on aircraft batteryvoltage. By careful positioning of the lamps, flare and shadow have been avoided. Test switches are provided, and the complete unit is mountedon a radio tray. It can be removed from the aircraft for servicing or calibration by withdrawing two pins, and the complete removaland disconnection from the aircraft can be effected in two minutes. A small double mirror fitting obviates parallax errors during cali-brations. Access to each side of the panel is by hinged covers. Variations of the basic unit have been built for various purposesbut the basic design is capable of providing up to 20 separate indications in a unit of small size, if the existing large S.A.E.case instruments are replaced by Dessyns or miniature instruments. (Left) The automatic observer, with lid raised to show dials. (Centre) Reproduction from film record of readings. (Right) Rear of the panel, showing the method of camera mounting.
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