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Aviation History
1949
1949 - 0965.PDF
624 FLIGHT MAY 25TH, 1949 Balliol Progress design of Balliol components. Fins and tail- planes are interchangeable, whilst elevators, ailerons, undercarriage legs and wing tanks are similarly interchangeable port and starboard. The difference associated with the Merlin- cngined Mark II in comparison with the Maraba-powered Mark I is slight. In maximum speed, it is chiefly a matter of height, the Mark I giving 307 m.p.h. at 20,000ft, and the Mark II 305 m.p.h. at 11,500ft. At io.oopft the Mark I has a maximum continuous cruise rating of 269 m.p.h., whilst at the same altitude the Mark II gives 280 m.p.h. at the rich mixture setting, and 240 m.p.h. on weak mixture. Although the Mamba is served with 169 gallons of fuel, whilst the Merlin has 125 gallons, and 140 lb has been saved in the struc- ture weight of the Mark II, the fact that the Merlin is some 830 lb heavier than the Mamba has been the greatest single factor in raising the all-up weight of the aircraft from 7,860 .lb tor the Mark I to 8,175 lb for the Mark II. But despite its 11J per cent greater power, the Merlin needs 10J min to take the Balliol up to 15,000ft as against the Mamba's 8| min. In terms of production, the Balliol gives evidence of causing no trouble. The design is straightforward and the production processes are uncomplicated; an example is the fact that uo removable fillets are used on the aircraft. No sheet-metal workers are employed on Balliols at Wolverhampton; double-curvature panels and components are all produced either in conjunction with soft- metal dies or wood-formers and rubber mattresses on com- pression presses, or tensioned over wooden formers on stretcher presses. Boulton Paul Aircraft have also announced that they have again started to design and manufacture under- carriages—the original company of Boulton and Paul, Ltd., were pioneers of oleo-pneumatic shock-absorber legs—and, of course, the Balliol employs an undercarriage of home ' pliotograph. Chiefly concerned with balliol graduation are, left to right: N\r. R. j^ director and general manager; Mr. J. D. North, managing director; anil Dr. S. C. Redshaw, director and chief engineer. manufacture. Uniquely, the main legs, together with their retraction mechanism, are each anchored in a box unit self contained and profiled to form part of the wing leading edge. The box is located on the front wing-spar by four dowels, and the changing of a complete undercarriage unit is therefore an extremely simple matter. A telescope of fairly long stroke is used, and the strut— together of course with the whole airframe—is designed to cater for a maximum sinking speed of i6ft/sec. This value is the latest specification figure for Naval aircraft. Technical Evidence An Appraisal of French Design-trends AT Orly, before the start of the afternoon's flying pro-gramme (a report on which appeared in last week's*" issue), it was possible to walk round and inspect the various types in the aircraft park, and to pick out some of their peculiarities for brief comment. To take the Sud-Ouest Bretagne 30P first, the workman- like and yet elegant appearance of the aircraft as a whole attracted immediate attention. With two Pratt and Whit- ney R-2800 B43 engines driving Curtiss-hubbed, Ratier- bladed airscrews of 73ft 5jin diameter, this 30-passenger transport has a cruising speed of 259 m.p.h. and a range of 934 miles. As an example both of power reserve and of confidence in the engines, on the day preceding the display the Bretagne was flown from Paris to Bordeaux and back to Paris on one engine only, a distance of 600 miles for the round trip. The Bretagne employs a tricycle undercarriage by Dis- positifs Oleo-Pneumatiques, the main legs employing a levered suspension cantilever axle whilst the upper part of the assembly is a light-alloy casting', the French favour magnesium. The nosewheeJ assembly also utilizes a light alloy casting for the upper portion of the strut, the sliding tube terminating in a "bell-crank " casting in which pivots the king-pin of the wheel fork. Another feature of the aircraft is the employment of s'jmi-Fowler-cum-s!otted flaps, that is to say, the main flap surfaces move rearward and downward in the normal Fowler manner but, in addition, have their trailing edges fitted with subsidiary slotted flaps. Provided the control linkage is such that some measure of variation in pivotal geometry is permitted, it would appear that this form of flap arrangement should provide enviable flexi- bility in catering for many more than usual lift/drag per- mutations. Named Mercure, the Breguet 892 high-wing freighter is a variant of the Type 890, which employs an opening rear portion of the fuselage for freight-loading purposes. In the 892, a large door on the starboard side is used. For freight handling, an in-built travelling crane with hoisting tackle is provided in the form of a thwartships beam carried on rollers in tracks along the fuselage walls. The beam is in two parts, the lower sliding on rollers relative to the upper, so that it can be extended out through the door for hoisting and lowering bulky or heavy freight. The rela- tionship of the door and the wing root is such that the tail of the starboard inboard nacelle is hinged across the top and swung upward by a screw jack in order to be clear of the beam hoist when the latter is extended outboard. The fuselage, 1,724 cu ft in volume (34ft x 7.5ft x 6.8ft), is readily convertible to seating accommodation for 40 passengers. The Mercure naturally has a stalky undercarriage in view of its wing/fuselage combination, and although the design
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