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Aviation History
1940
1940 - 1640.PDF
JUNE 6, 1940 The somewhat unorthodox layout of the DB-7 is wel1 shown in this ground view. The machine illustrated was the first of the French order. the wing, for example, is made up of four separate sec- tions, the fuselage of three and the tail unit of seven. It is pointed out that, besides simplifying shipment, this feature is extremely valuable in the event of damage as a complete unit can be speedily replaced. The Northrop plant (now known as the El Segundo Division of the Douglas Aircraft Company)- was unable to deal with the orders and now only the fuselages are being built there, all other work, including wing construction and final assembly, being done in the main factory at Santa Monica. The Douglas DB7-B3 (three-seater bomber) is a shoulder- wing monoplane with sharply tapered wings and a fairly deep, narrow fuselage with a characteristic sweep up from the bomb bay to the tail. The greater part of the nose is transparent and provision is made for two or four fixed machine guns firing forward through ports in the lower part of the nose. One free gun is carried on a shielded manually operated mounting on top of the fuselage and there may be provision for a second gun to fire through the floor downward and to the rear. The prototype had a rotatable turret but this seems to have been entirely abandoned. The engine nacelles extend tor about two feet behind the trailing edge of the wing and house the rear wheels of the undercarriage in their raised position. Like the nose wheel, the rear wheels have a single oleo strut each; the nose wheel retracts rearward upward into the fuselage, being covered when raised by hinged panels. The nose wheel undercarriage, of course, is typical of most recent Douglas designs and is claimed to offer a number of advantages for military operation. Apparently the first machines to be delivered are fitted with Pratt and Whitney Twin Wasp R-1830 SC3-G engines. These units have a normal rated output on 87 octane fuel of 900 h.p. at 2,250 r.p.m. at 12,000 ft., the maximum cruis- ing output being 650 h.p. at 2,250 r.p.m. at 15,500 ft. The take-off rating is 1,050 h.p. at 2,700 r.p.m. ; this is the "five-minute" rated output for military use up to 7,700 ft. the other maximum rating being 1,000 h.p. at 2,800 r.p.m. at 11,500 ft. Hamilton Hydromatic fully feathering airscrews are specified. It will be gathered from the accompanying illustration that there is a single tall fin and rudder of typical Douglas design and that there is a pronounced dihedral on the tail- plane. A faired bulge below the tail protects the rear of the machine should it strike the ground. A crew of three is normally carried and the bombs are stowed internally in the bottom of the. fuselage. The possibility of employing the machine as a dive-bomber has been mentioned but no details have been released of any diving brakes which may .have been fitted. The DB7-B3 is obviously a formidable addition to the equipment of L'Armee de VAir in company with the Martin 167F described in the last issue of Flight. : DOUGLAS DB-7. ! Two Pratt and Whitney • Engines. : DIMENSIONS • Length : Height: Wing area | WEIGHTS A • Weight, empty • Disposable load• Gross weight • Wing loading ...• Power loading Twin Wasp 61ft. 4in.47ft. 15ft. lOin.464.8 sq. ft. ND LOADINGS • PERFORMANCE : Top speed : Cruising speed: Service ceiling (one engine) ... :' Cruising range (approx.) ... 11,400 1b. 3,630 lb.15,030 lb. 32.3 lb./sq. ft.8.35 lb./h.p 320 m.p.h. 280 m.p.h.17,000ft. 1,200 miles,.
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