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Aviation History
1950
1950 - 0347.PDF
FLIGHT. 16 February 1950 are interchangeable port and starboard, and are rubber sprung. The nosewheel has an oleo shock absorber, is fully castering, and has a Marstrand anti-shimmy tyre. Pneumatic wheel brakes are operated by a thumb lever on the control column, with differential steering operated by the rudder pedals. A version with a pneumatic- ally operated retractable undercarriage can be supplied to special order. Dual control is provided for the crew of two, and the cockpit layout, except for minor details, is exactly the same as that of the Dove. It will be recalled that pilots think highly of the Dove cockpit layout and of the very good all- round view afforded. The cockpit roof is of opaque Fibreglass. Space is provided for the! following radio equipment: Marconi AD 97/108 transmitter-receiver, which can be arranged to proiade W/T or R/T communication on medium and high frequencies; a Marconi Auto-^ matic Radio compass (AD 7092) working on medium and low frequencies; and also for a Standard Telephones S.T.R.12 V.H.F. transmitter-receiver and Marconi blind-approach equipment. The Gipsy Queen 30 engines and the,, D.H. 1,000-size 7ft diameter, constant-speed airscrews are well tried and are likely to prove very reliable. Overhaul lives of the two . are respectively 750 and 800 hours. The Queen 30 is a straightforward development of the earlier Gipsy Six and is in general use in the Prentice basic trainer, while the air- screws are of the same type as those used on the Prentice and the Proctor. Power and ancillary services are similar to those of the Dove. Flaps and brakes are pneumatically operated, pres- sure being maintained by Hymatic compressors, one on each outboard engine. The outboard engines also drive two 24-volt 1,000-watt generators which supply the two accumulators stowed in the starboard side of the aircraft nose. Circuit-breakers are used in place of fuses. The fuel tanks are of a bag type (one on each side of each wing-root spar) and according to requirements may have a total capacity of 200 or 300 gallons. They hold 100 (rear) and 50 gall (front) and have Plessey immersed-type fuel pumps. A cross-feed cock makes it possible for each of the tank- groups to supply any engine. Inboard engines carry Plessey vacuum pumps to drive the blind-flying instruments and, if fitted, the Sperry gyropilot A.L.I. Air from .the pressure side of the vacuum pumps is used to operate the Goodrich wing and tail de- icing boots. The airscrews have fluid de-icing. The normal cabin layout accommodates 14 passengers, baggage compartment and toilet, but a slight rearrange- ment of this will enable a fifteenth passenger seat to be fitted. If the toilet compartment is removed and the luggage hold reduced in capacity, the maximum of 17 seats can be accommodated. The internal width of the cabin is 4ft 6in and the head room for the whole length is 5ft 8Jin. Dove-type chairs, which have no rear legs, and therefore give unhindered foot room, are fitted at 32-inch pitch. Fourteen rectangular windows of the same size as those on the Dove will give his sfigne during-£onstruction. the passengers a good view and provide good lighting for the cabin. A separate cold-air ventilator is provided for each passenger, and cabin heat is controlled by the pilot. Mainly because the Heron is a little larger, the operating costs per ton-mile of payload will be a little less than for the Dove. These costs, in pence per ton-mile, have been estimated by the standard S.B.A.C. method to permit direct comparison with current types of aircraft. The figures for price and engine-life used in preparing the accompanying graphs are those already quoted. In addi- tion, it is assumed that there will be a crew of two, that maximum w.m. power per engine is 193 b.h.p., and that the fuel cost is is 8d per gallon. Cruising power is taken as 60 per cent of take-off power. The performance summary for the Heron at 12,500 1b all-up weight in standard conditions and with full standard equipment including radio, is tabulated below. For the version with retractable undercarriage, the recommended cruising speed at 8,000ft on 60 per cent power is 175 m.p.h. The figure for a.m.p.g. is increased from 4.15 to 4.5, and the rate of climb with one engine out is increased from 340 ft/min to 400 ft/min. , PERFORMANCE DATA Recommended cruising spaed it 60 par cant powar, it 8,000ft ... 1(0 m.p.h. Corraipondinf fual consumption 39 gall/hr Corresponding air milas par gall 4.15 Max w.m. cruising spaad at 3,000ft 177 m.p.h. Rata of climb at saa laral 1,200ft/min Service ceiling 18.500ft Rata of climb, 3 anginas, at 5,000ft 340 ft/min Taka-off to 50ft in still air from dry grass surface using airlina technique 700yd Take-off distance to 50ft when ona angina failt at safety spaad (still air, dry grass surfaca) 800yd Taka-off distance to 50ft at 12,000 Ib a.u.w. (still air, dry grasa surfaca) 650yd Landing distance from 50ft (still air, dry grass surfaca) 450yd WEIGHTS Tare weight, including 14 chairs, toilet compartment, and radio 7,9601b Crew of two 3301b Fuel 183 gall (400 miles stage length with allowances) ... 1,316 Ib OiM6gall 1441b Payload 1.750 Ib All-up weight ... 12,5001b The first Heron -nearing completion at the Hatficld factory,^
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