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Aviation History
1959
1959 - 0230.PDF
FLIGHT, 16 January 1959 105 Radio Distress Beacon A PROMISING CANADIAN CRASH-LOCATOR AEROPLANE crashes are, in general, becoming increasinglyi\^ disastrous. Owing to the high speeds involved, demolition X A. of the aircraft is becoming progressively more frequent andit is often the case that no conscious survivors are left at all. For a considerable period, the National Research Council of Canadahave been investigating possible systems whereby the location of a crash can be determined precisely and rapidly, irrespective ofwhether or not anybody on board the stricken machine can offer any assistance. From a wide range of possible solutions it wasdecided to choose a radio beacon; this provides a long-range, high- altitude, accurate, all-weather means of detection using a light-weight, non-hazardous apparatus which can be carried by all aircraft. A recent report (N.R.C. report MR-22, by H. T. Stevinsonand D. Makow) describes the development of the beacon. The search equipment is not dealt with, since it is considered that theSARAH system, developed by Ultra Electric and widely used by the R.C.A.F., is completely satisfactory. It was essential to evolve a beacon which can be carried by anyaeroplane, which can operate for several days in ambient con- ditions ranging from arctic to tropical and which can be deliveredsafely from a crashing aircraft. The last-named requirement implies deceleration of a very high degree (but still only a fractionof that to which most portions of the aircraft and its equipment are subjected). Moreover, the beacon requires a fast-acting crashdetector and on/off switch, and ability to operate after alighting on a surface which can be hard, soft, liquid, rough, smooth, flat orslanted, or covered in deep snow. The solution decided upon employs a very light, flat, pulse-modulated transmitter distributed across a thin parallel-plate aerial. This package is then potted in tough plastic foam forminga dome-shaped aerofoil section, completely covered with a lamin- ated skin of nylon fabric and polyester resin. Upon receipt of the earliest possible symptoms of a crash thisdevice is released, whereupon it tumbles away, rapidly decelerates to a safe landing speed, absorbs its own landing shock and, regard-less of its orientation, transmits a signal for several days. It also behaves as a snow-shoe, and in water floats with 85 per cent ofthe package exposed to maintain the internal aerial clear of the water or muskeg. It is expected that transonic and supersonicaircraft would employ a sharp-edged model so mounted in a shallow depression as to produce no modification to the exteriorprofile. After release, the beacon forms a tumbling aerofoil. By suitably placing the centre of gravity the device can be made tocontinue to rotate rapidly after release, while at the same time generating an average overall lift to curve it away from the wreck.An accompanying sketch shows the radio beacon, without its surrounding shock-absorbing aerofoil. The aerofoil is 28in squareand 5 to 6in thick at the dome. It weighs 11.5 lb and carries a 5 lb beacon which will operate for 84 hr at —40 deg F. The beaconitself is powered by a 16V battery consisting of twelve nickel- cadmium cells, a 1.3V filament supply being provided by five ni-cdcells in the diagram (respectively B and A). The parallel line push- pull transmitter is placed in the centre, and employs two miniaturetriodes which are tightly closed by a metal foil which makes con- tact with the upper 14in aerial plate. For an assumed acceptablemean range of eight miles, the required peak output is 3.2W. A total of 104 experiments had been carried out when the reportwas written. In simulated crashes 11 tests employed models hung from a car, 32 models were dropped from a 200ft tower andtwo were fired into the base of a cliff from rocket sleds. The first sled firing used a 1\ lb tumbling beacon mounted in a socket withan outside profile simulating the skin of an F-86 Sabre aft of the starboard dive brake. Deployment was initiated by a bank ofcoiled springs when the sled was travelling at 120 m.p.h. Failure of the last attachment slipper to unlock caused a shock which torethe socket apart and released the beacon about 50ft from the point at which the sled nose met the cliff; the beacon flew about 20ftvertically and 70ft horizontally and landed unharmed at about 13 m.p.h. near the top of the cliff. The second sled was fitted witha redesigned flat-domed beacon which was released—again not quite according to plan—at about 230 m.p.h.; the beacon tumbledrapidly up to a height of about 60ft, clearing a horizontal safety fence by a wide margin and landing almost unscratched on the rearface of the hill. In the next phase of development, eight beacons were releasedfrom aircraft, most trials involving Beech Expediters (Twin-Beech, Model 18) at speeds up to the maximum allowable of 227 kt indives. No trim or speed change could be detected with certainty OSC", A* NtNN MATCHING urnr -J General arrangement of the beacon transmitter. Around it is arranged a protecting envelope of foam, with a lifting-aerofoil profile in any drop. After investigating release while taxying at 80 kt,flying at 90 kt at 5,000ft and diving at 140 and 227 kt, two drops were made with a more powerful beacon at 160 kt from a height of150ft on to a snow-covered hillside forested with pine-trees. In both the latter cases the beacon came to rest entirely above thesnow, worked normally until shut off and gave full R.F. output when subsequently measured in the laboratory. Finally 49 range-test search flights were made with Expediters (one equipped with SARAH) at around 9,000ft. At the time of writing, 70 miles couldbe obtained under the most favourable conditions, ten to 30 miles under good conditions and at least five miles under the most severeconditions, in each case with complete reliability. Greater ranges are now being obtained with a more powerful push-pull beacon. Total experience with the Expediter has demonstrated the satis-factory operation of all parts of the system. It is expected that a tumbling beacon mounted above the tail and fitted with triggerwires on the nose and wings would survive a wide range of possible crashes with this type of aircraft. On larger aircraft it maybe necessary to have a second beacon on the under-surface for use during upside-down impacts. The system has not been deployedbeyond 260 m.p.h. or shocked beyond an estimated 70g impact, but experience indicates that the beacon will stand much more severelandings than any so far made. The filament-pulse signal aids immediate recognition and reduces battery requirements by afactor of at least two. Several other types of radio beacon for locating either crashedaircraft or survivors have recently been developed for civil use, but it is worth noting that an entirely different line is being followedin providing built-in clues to help determine the cause of accidents. The American Federal Aviation Agency (formerly the C.A.A.) hasstipulated that all turbine-powered civil aircraft operating at heights above 25,000ft shall carry a tape-recorder making a recordof the main flight parameters, such as speed, height, acceleration and heading. As far as possible, the unit should be indestructible,in order to survive a crash. A similar regulation has been pro- posed by the French authorities. CANADIAN INDUSTRY'S FUTURE N Mr. James Young, founder and chairman of theCanadian Pratt and Whitney Aircraft Co., retired on Decem- ber 31 at the age of 75, he said that the Canadian aircraft manu-facturing industry was entering a period of change which would probably see it employing fewer people in the future on the build-ing of aircraft owing to the shift towards missiles. But he foresaw a great increase in all forms of civil flying and a correspondinggrowth in the facilities necessary for it, though there would be a continuing military need for reconnaissance and transportaircraft. Mr. Young, who founded Canadian Pratt and Whitney thirtyyears ago, commented that his firm was unique among Canadian aircraft manufacturing companies (apart from de HavillandCanada) in that it did a large export business of about $20m a year, trading with 50 or more countries and earning a large amountof U.S. dollar exchange. The company had only ten employees when Mr. Young started it in 1928; it now has two big plants onthe south shore of St. Lawrence, facing Montreal, and about 2 3000men and women on its payroll. •x
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