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Aviation History
1957
1957 - 0428.PDF
430 FLIGHT DOUGLAS 1940 Santa Monica's Own DCS Replacement "Flight** copyright drawing DURING the past decade the game of designing an aero-plane to replace the ubiquitous DC-3 has been played in adozen countries without any conclusive results. Now Douglas Aircraft have themselves written down a specification forwhat they feel ought to be done and have issued it to prospective customers to see what reception is accorded. Aircraft of thisgeneral type have been bandied about at Santa Monica for years, but it is only within the last few months that the Model 1940 hasbecome firm. Diagrams below indicate floor plans and a cross section of theusable portion of fuselage. The interior width at floor level is 132in, sufficient to allow triple seat units to be installed on bothsides of an 18in central aisle. When seats are installed at the 40in pitch corresponding to the window spacing a total of 60 passengerscan be accommodated, together with a forward freight compart- ment of 164 cu ft, an aft freight compartment of 143 cu ft andcarry-on baggage bays totalling 135 cu ft flanking the main passenger door. From the flight deck to station 520 (roughly amidships) thefloor is stressed to support cargo at 200 lb/sq ft at a maximum longitudinal distribution of 100 lb/in. The seats in this regioncan be folded and removed so that, when the floor is cleared back to station 520, 18 passengers can be accommodated (withthe carry-on baggage and rear cargo compartments) together with 15,000 lb of cargo in the 1,557 cu ft space ahead of the movablebulkhead. Cargo is loaded through a door 60in high and either 48 or 75in wide (according to customer preference) on the star-board side immediately behind the flight deck. Douglas have chosen to pressurize the cabin even though theroutes for which the 1940 is designed would restrict the aircraft to essentially low-altitude operation. A maximum operatingdifferential of 4.16 Ib/sq in has been chosen, to increase the flexibility of operation and to provide a more comfortable ridefor passengers; it is also, of course, a great help to maintain sea-level pressure during rapid climbs and descents and when airis turbulent at low altitudes. Cabin air is drawn from engine- driven compressors and is then cooled by a heat exchanger (backedup by a Freon evaporater) or heated by electric resistances. All the illustrations on this page refer to the basic Douglas Model 1940. The cross-section (right) indicates widths in inches. Key to the floor plans: A, tie- downs at 2in spacing; B, freight floor; C, buffet; D, 143 cu ft cargo; E, coats; F, tip-up seat; G, carry-on baggage; H, 164 cu ft cargo in passenger version. — t * • \ : Douglas have also planned a Model 1940A civil/military utilitytransport with an unpressurized fuselage and floor 220in long and 116in wide, stressed to take freight at 300 lb/sq ft. The1940A has an upswept rear fuselage with rear doors 98in high by lOOin wide admitting a 12-deg ramp at a typical truck-bedheight of 50in above ground level. It is at present envisaged that the A-model will have a "universal" undercarriage with attach-ments for skis through which the wheels will project for hard- surface operations. Data for this special type follow those for thebasic Model 1940. During its early life the 1940 project featured all kinds ofhigh-lift devices, including a variable-incidence wing and/or blown flaps or boundary-layer control. In the finalized designthe wing is quite straightforward, though it has been fitted with a very effective flap system for operation at lift coefficients whichmust approximate to 3. Double-slotted flaps of no less than 40-per-cent chord extend from root to tip on each mainplane, andleading-edge flaps of 15-per-cent chord are employed to improve the flow at high angles of attack. The full-span flaps do notdouble as ailerons; control in the rolling plane is effected by slot- lip spoiler segments actuated by hydraulic rams. The rudderand elevators are manually operated via spring tabs. Douglas have a high regard for the Rolls-Royce Dart 510 inview of the British engine's proven reliability and effectiveness as a commercial transport powerplant. Four Dart 510s wouldfit the 1940 admirably, and should eliminate any chance of the programme being held up through powerplant unavailability. Standard powerplant for the new Douglas is, however, the (Concluded at foot of page 432) DOUGLAS 1940 (Four 1,500 s.h.p. Lycoming LTC4A-1 turbines) Dimensions: span, 102ft 6in; length, 92ft 6in; height, to fin-tip on ground at maximum weight, 36ft 8in; gross wing area, 1,300 sq ft; tailplane span, 42ft 8in; track, 12ft 2in; wheelbase, 29ft 10in; body cross-section, 152in wide by 144in high Weights; empty (typical), 39.350 Ib; basic operating, 40,815 Ib; capacity payload, 15,000 1b; capacity fuel, 26,000 1b; maximum gross, 65,500 1b; maximum landing, 65,000 Ib; zero-fuel, 56,000 Ib. Performance: maximum weight take-off field length, s.l., standard day, 20-deg flap, 2,330ft; landing at 65,000 1b, 50-deg flap, 3,000ft; landing at 59,600 1b, 2,770ft; range with maximum payload, 560 n.m.; range with 10,0001b payload, 1,075 n.m.; typical cruising speed, 261 kt; performance on 300 n.m. stage: take-off at 63,1001b with maximum payload, field length, 2,121ft; block time 1 hr 22 mm, A.T.A. cost 1.4 cents'200-lb n.m.; performance on 80 n.m. stage: as above, except, block speed 153 kt, fuel consumed 1,269 Ib in 31 min (10 min for taxying, take-off and landing), leaving 5,7101b reserve. A.T.A. cost 2 cents 200-lb n.m.; D.O.C. falls from $2.1 per aircraft n.m. on 50 n.m. stage through $1.15 at 200 miles to $1 at 600 miles. Model 1940A Generally as above, except: maximum payload, 16,0001b; maximum landing weight, 59,100 Ib; range, 1,590 n.m. cruising at 243 kt.
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