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Aviation History
1947
1947 - 1439.PDF
AUGUST 1947 FLIGHT 223 Miles Merchantman ..... monospar (30 per cent) structure, although at 70 per cent chord a light-pressed channel member can be considered as a rear spar. The leading edge is a D-box internallystrengthened by braced formers at 6in centres. Between the engines, however, a false spar at 7^ per cent chord forms the rear closure to leading-edge nose tanks for engine oil supply. It may be mentioned here that the tail lairings of the engine nacelles, i.e., the whole portion behind the firewalls, are formed as fuel tanks. To return to the wing structure, intcrspar ribs are Warren girder braced units built up with channel members, and are pitched at I2in centres. Trailing-edge ribs are diaphragm pressings throughout and, at engine bay, flap and aileron hinge stations, external doubling plates transfer load over the leading-edge, interspar and trailing edge ribs. From tone rib station outboard of the roots to one rib inboard of"f •• detachable tips the trailing edge rearward of the 70 per ' spar is fabric covered. Commander T. F. Caldwell, first record breaker, with the U.S. Navy Douglas Skystreak. NOT long ago the Ministry of Supply stated that noBritish attempt on the air-speed record would be madethis year, but that in 1948 another attempt might be made to regain the record which was at that time heldby a special U.S. Army Air Force Shooting Star with a speed of 623.8 m.p.h. At Muroc, on August 21st and again onAugust 26th, this speed was very considerably improved by a U.S. Navy Douglas D-558 or Skystreak. The taskof bettering the latest record speed of 650.6 m.p.h. (subject to F.A.I, homologation) will be a very formidableone. The fastest run over the 3 km course during the attempts is reported to have beenmade at 653.4 m.p.h. The Skystreak is one oftwo such machines ordered by the U.S. Navy forhigh-speed research, and ithc tvpe was announced * f, christened early thisar. The construction is quite conventional butthere are several interest- ing design features. Theengine is a General-Electric TG-180 axial-flow turbojet, a type which has a maximum power ratingof 4,000 lb thrust. DOUGLAS General-Electric 558 TG-ISO (4,000 1b thrust) Snan .." Length Height Wing Area Wing Loading ... Gross Weight ... ... 25ft 3S!t Uin 12ft Uin 150 sq ft 65 Ib/sq ft 9,750 Ib The tail boom is a very simple structure built up on four channel-section longerons, which are spanned by drawn round-channel booms braced by tubular struts to form Warren girders The skin papelling has integral pressed swagings at Sin centres for stabilizing Attachment to the fuselage is made at each longeron terminal, the upper joints being made with through bolted transfer straps whilst the lower joints employ fore-and-aft bolted forged end-fittings In order to get the first prototype into the air with the least delay, the tail surfaces are of wood Production air- craft will, however, use all-metal surfaces, and there is every likelihood that the structural form employed will be akin to that evolved for the Seabee; this has not yet been finally decided. To sum up, the Merchantman can be regarded quite fairly as being an exceptional aircraft which, on the strength of the Aerovan's popularity, may confidently be expected to enjoy widespread employment. It has patently been de signed for rapid and simple production, it is robust, and it is workmanlike. These qualities aie always in demand New Speed Records U.S. Navy Research Aircraft Achieves 650 m.p.h. Extensive use is made ct magnesiumalloy for the fuselage structure. The whole nose section is jettisonable, and inemergency the pilot would free his cock- pit from the rest cf the aircraft, waitfor speed to decrease and then bale out, more or less normally. That portion ofthe fuselage which is not occupied by the cockpit or recording instruments is en-tirely taken up by the power unit and its jet pipe, internal fuel tanks are thereforeconfined to the small thin-section wings, Two integral tanks containing a total of 230 gallons are con-tained in the wings, but provision is made for t\ o 50-gallon diop tanks to be carried. When empty these auxiliary tankscan be jettisoned with the aid of small explosive charges. The total of 330 gallons of fuel is stated to be sufficient for a flightof 90 minutes' duration. In view of the tnin section ot the wing the aileron balanceweights presented some difficulty, and the Skystreak is now fitted with weights of tungsten alloy with a density 50 percent greater than lead. Space problems have also led to the use of very small wheels and high-pressure 8-ply nylon tyres.irajated to 250 lb/sq in. v' The whole airframe is stressed for a safe working factor of I2g and a breaking load factor of i8g. This, it is calcu-lated, will safeguard the machine up to a Mach number of \. Cockpit Temperatures and Pressures The pilot's cockpit is pressurized and cooled, sea-fevel pres-sure being maintained to 8,000ft, 8,000ft pressure to 22,000ft, and above 22.000ft a differential pressure of 4 lb/sq in. Cabintemperature which might at sea level rise to as much as 180 deg F, will be limited to a maximum of 105 deg F. Thepilot sits between the bifurcated air entry ducts for the engine, the single intake orifice in the nose being vertically dividedto feed through the two ducts. The raising of the existing air-speed record first by 17 m.p.h.and then by 27 m.p.h. is a great credit to Douglas technicians and to the pilots ' ommander Turner F Caldwell, who is 33years old, is a U.S. Navy fighter pilot. He made four runs during his record attempt, two in each direction, at an alti-tude of 75 metres. Majoi Marion Carl, who raised the record the second time, t< 650.6 m.p.h., is a U.S. Marine. His firstdown-wind run was made at 652.6 m.p.h. The Skystreak was not modified in any way tor therecords and no special fuels, injection or after-burning were used to increase the thrust ot the General-Electric power unit. Further technical details of the Skystreak and the conditionsr\t the time of the records are awaited.
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