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Aviation History
1955
1955 - 0170.PDF
170 FLIGHT, 11 February 1955 INTEGRATED FLIGHT SYSTEM . . . instructions from computed heading-displacement, beam-displace-ment and bank signals. A "kinked" localizer beam will cause the steering needle to nicker, and an average reading should thenbe used. To overshoot, the pilot sets the I.L.S./HDG switch to HDGand, using the heading pointer and steering needle, climbs away as instructed. If, on some occasion, a back-beam approach isnecessary, the course arrow is set to the I.L.S. in-bound course, the heading pointer on the tail of the course arrow, andI.L.S./HDG switch to HDG. The back beam can then be followed with the steering needle and any wind-drift whichbecomes apparent can be counteracted in the normal way by offsetting the heading pointer. The I.L.S. beam is thereafterhandled in much the same way as a y.A.R. beacon. The foregoing description may give the impression that theIntegrated Flight System is over-complicated. Actually, how- ever, it has a great advantage, in that the indications from boththe course indicator and the approach horizon are as far as possible directly pictorial and incorporate attitude reference, and also thatthe indications are given in the natural sense. Perhaps one of the most difficult parts of flying with radio navigation equipmentis the mental interpretation required to make sense of a number of readings in relation to a desired flight-path. Aural signals inparticular require practice and concentration by the pilot if he is to interpret them correctly when busy—for example, during anapproach in really bad weather. Anyone with experience of S.B.A. approaches will be fully aware of this problem. The I.L.S.cross-pointers with their blue and yellow lefts and rights also require practice and correct interpretation. The Collins system on the other hand, supplies computed,pictorial indications which can be followed directly to produce a desired result. Hunting, and overshooting of either the glideslope or the localizer beam, can more easily be avoided because the steering needle and pitch bar indications are designed to feedthe aircraft on to the beam, so to speak, rather than to tell the pilot how far away from it he is. With the FD-104 controlling an autopilot on an I.L.S. approach,furthermore, the Integrated Flight System instruments are probably the easiest way of monitoring the functioning of theautopilot. One need only watch the comparative behaviour of one of these instruments and an I.L.S. cross-pointer meter toappreciate the value of the Integrated Flight System. PLASTIC DROP-TANKS FROM FILTON DROP tanks, as used for extend-ing the range of fighters, are an item of equipment often taken forgranted. They are not, however, quite such simple components as isgenerally assumed, nor are thev par- ticularly cheap; it is said, for instance,that they constituted the largest item of expenditure by the U.S.A.F. in theKorean War, when thousands were dropped every week—and they costbetween £200 and £300 each. With a view to economizing bothin cost and in the use of strategic material there is now a move in thedirection of using plastics in place of light alloys for the manufacture ofdrop tanks. The first cost of the plastic tank is stated to be between 25 and 30per cent less than that of its alu- minium equivalent. It is not generally known that forthe past three years the Bristol Aero- plane Co. has been carrying out adevelopment programme for the de- sign and manufacture of a standardtype of plastic tank and that large- scale production is now being plannedfollowing the receipt of M.o.S. orders. These orders were an outcome of theplan for standardizing drop tank sizes on new (and where possibleexisting) Service aircraft. Standard- ization will, of course, greatly assistmass production. The standard sizes so far developed at Bristols have capa-cities of 50, 100, 150, 200, 300, and 500 gal. Further standardizationhas been achieved by making the front tand rear shells of the 100 and 150 galtanks identical, the larger tank having a longer centre shell; in addition, the200- and 300-gal tanks have com- mon front and rear shells. Production processes used are adapted from those developed bythe company in early work on primary aircraft structures in plas- tics. Cylindrical fuselage sections were moulded by the autoclaveprocess and frames and wing sections by hydraulic press mould- ing, and these procedures proved adaptable for, respectively, thedrop tank shell and the internal framework. The material used is asbestos felt impregnated with phenolic resin; a "short-fibre"asbestos (instead of the long fibre generally used in aircraft work) is employed, since supplies are plentiful. The three main shell•sections have high-pressure-moulded internal frames assembled by hot gluing. The basic aerodynamic design is by the R.A.E.,but the structural design is by Bristols, and a number of the production methods employed are covered by the company'spatents. The three-section method of construction simplifies storage,for the shells of several tanks can be placed together to give a nesting ratio of about 3:1. The sections can, it is stated, beassembled in the field by two or three unskilled men in under Bristol plastic tank for Hawker Sea Hawk. 15 minutes; no adhesive is required and the only tool necessaryis a screwdriver. Provision is made for various types of air/fuel connection to be screwed into the tank ports to meet varyingdesign requirements, and an automatic float switch can also be fitted for use with pressure fuelling. The pick-up point on the tank is designed to fit the standardbomb or under-wing store-attachment point; it can also be readily adapted to fit the two-lug American-type mounting or a jettison-gun mounting. A fin—adjustable in incidence to suit the characteristics ofparticular aircraft—is fitted to counteract any pitching moment and thus ensure a clean fall-away. Plastic tanks can be given a finer surface finish than aluminiumtanks, and the surface can, of course, be painted in any colour desired. The material used is unaffected by extremes of tem-perature or humidity, and Bristol plastic tanks have already been used successfully in Africa. A metal cap, moulded integrallywith the shell, is fitted to the nose of each tank to reduce erosion by hail and rain. It is stated that the 100-gal tank adopted forthe Hawker Hunter has been flown on that aircraft at supersonic speeds without affecting performance.In addition to the standard range of tanks the Bristol company has developed versions for certain aircraft already in production;identical in shape (and comparable in weight) with their metal counterparts, these tanks cost considerably less. One exampleis a 250-gal wing tank for the Canberra, and others include the pylon tank for the Sea Hawk and pylon and tip tanks for theVenom. Design and development, state the Bristol company, is in fact proceeding with drop tanks for the majority of front-lineBritish aircraft. ALAN MARSH MEMORIAL FUND AS briefly announced last week, the Helicopter Association has• set up a trust fund in memory of the late Henry Alan Marsh, A.F.C., A.F.R.Ae.S. It is to commemorate "his inspiring andselfless devotion to the development of rotating-wing aircraft, and the prominent place that he took in forming the Helicopter Asso-ciation of Great Britain." The memorial is to take two forms: monetary grants to bemade to assist the careers of young persons employed in the heli- copter and associated industries, and medals to be awarded toindividuals for outstanding work in any of the fields associated with the science and practice of helicopter engineering andoperation. Trustees appointed by the Helicopter Association are Messrs.R. A. C. Brie, L. G. Frise, W. G. Leslie, and H. Grinsted. The fund has been opened with a gift of 50 guineas from the Associa-tion and another of £250 from Mr. A. J. Mollart of the Mollart Engineering Co. Contributions, now invited by the Association,can take the form of donations or annual subscriptions, the latter preferably under "deed of covenant" over a period of seven yearsin order that the trust may apply for refund of income tax upon them. Contributions should be addressed to the Alan MarshMemorial Trust, c/o The Helicopter Association of Great Britain, 4 The Sanctuary, Westminster, London, S.W.I. Alan Marsh, who lost his life at the age of 49, while testing theCierva Air Horse in 1950, first started flying rotating-wing aircraft when he joined the Cierva Autogiro Co. in 1932. Altogether,3,500 of his 6,500 hours of flying were on aircraft of this type.
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