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Aviation History
1962
1962 - 0674.PDF
DEFUELING PRESS. FUELING STATION RESERVOIR FEED BOX GRAVITY FILL FLIGHT International, 26 April 1962 A due to the latest US transport practice is provided by the three system diagrams published on this and the facing page. Above is a schematic representation of the fuel system DOUGL A:SI2,0 8 6;.|.«. with square windows. Maximum takeoff weight for the BAC air liner is 73,5001b, against 69,0001b for the 2086. Douglas designers, by their own admission, did not attempt to be original in aerody namics, structures, operations or anything else; "We stuck to known facts and kept reliability high by not trying to push the state of the art." They particularly want to be successful in certain practical areas affecting maintenance and overhaul. In performance they claim, perhaps immodestly, that their plane will do better than the one they copied it from. In retrospect this sounds like variations on the familiar theme of DC-8 versus 707. Handling characteristics will be "the same as the DC-8 in its class," whatever that means. The text following is based on the profile now being given to US airlines. Whether everything will work out as anticipated is rank speculation; but it should be noted that airlines have lately insisted that manufacturers live up to their brochuremanship. Realistically, the Douglas design group accept that the aeroplane they offer and the one most airlines want to buy will probably differ in several respects. Performance Douglas consider the DC-6B to be a reasonable standard on which to base takeoff and landing performance. The criterion is: if the DC-6B can get into and out of an airfield, so can the 2086. Since the latter is aimed at the short-haul market, a runway length of 5,000ft must be adequate at the maximum takeoff weight of 69,0001b. A total of 64 mixed-class passengers and baggage can be carried for 750 miles, 74 coach passengers for 530 miles, or 56 first-class passengers for 930 miles. According to the brochure, "Model 2086 has been designed to provide operation from a 5,200ft field on an 86°F day at sea level with 64 mixed-class passengers and their baggage for a 400-mile range segment. On a standard day, weight-limit payload of 17,9151b can be carried 245 miles from a 5,030ft field." There is to be sufficient scope in the design to allow for a growth version, should it prove desirable. Fuselage fuel in a centre-section tank is contemplated as a method of increasing range. In view'of the airline service to be performed, considerations of speed become secondary to those of flexibility along short routes. Cruise speed at 25,000ft with the two Pratt & Whitney JTF10A-6 turbofans at maximum cruise thrust is given as 530 m.p.h., or M0.76. Higher speeds in growth versions with higher-thrust engines—Douglas mention the Rolls-Royce RB.163-2—are possible, owing to the good drag-rise characteristics of the wing. For short stages there is little speed advantage in cruising at only 15,000ft with maximum cruise thrust. Block times on short hauls would vary only slightly with altitude but, while the 2086 is aimed at the local market, a growth version with larger engines could make higher cruising speed over a longer sector very desirable. Douglas claim that placard speeds will be some 20 m.p.h. up on those for the One- Eleven. This is said to be competitively important, since the type will be able to fly a very flexible operating profile over its short routes taking advantage of higher rates of climb and descent, Landing performance is hopefully described as "excellent." At sea level the CAR landing field-length is 5,300ft at the maximum landing weight of 65,8001b. The latter figure allows 5,8001b of fuel with the full design payload of 17,9151b. The maximum takeoff weight is set at 105 per cent of maximum landing to eliminate a fuel-dumping system. Configuration Douglas avoided the unusual in model 2086. The rear-mounted engine pods are strictly conventional, and the com pany avoided burying the engines to avoid design and production problems. Their design department may have lacked the courage to go out into the unknown and innovate, but it must be borne in mind that after mustering enough courage to stay in the com mercial airframe market with a new aircraft, there was insufficient of that valuable commodity called money to back a more radical approach. Craven perhaps, but safe. The two Pratt & Whitney JTF10A-6 turbofans are based on the military TF30 originally planned to power the cancelled Navy Missileer—also by Douglas—and have an ancestry going straight back to the original JTF10 planned in 1959 to power the still born DC-9 with four underwing engines. Bare engine weight is 2,3901b, and s.f.c. at max cruise thrust at 25,000ft is given as 0.805. Development on the military engine has continued, and test flights are being made with ohe hanging in a pod below the belly of a B-45. Current plans are to use the military JTF10A-20 in the biservice F-111A tactical fighter origin ally designated TFX. This advanced military version of the engine is said to produce 10,7501b thrust at sea level without afterburner, with much growth potential in hand. As already noted, Douglas mentioned that a growth version of the 2086 using Rolls-Royce RB.163 Spey engines is being considered. As in the case of the JT8D, Pratt & Whitney have adopted the Rolls-Royce policy of mixing the hot and cold exhaust flows in a single nozzle; no announcement has been made regarding noise suppression, but pneumatically actuated cascade-type reverters (again appearing to owe something to RR) will be provided for use on the ground. Each nacelle is supported from horizontal pylons, and the whole central portion takes the form of hinged upper and lower doors. Flight deck of the 2086 is neat but conventional. Visibility is virtually the same as that of the DC-8, on which the front-end design is based. The crew of two (no engineer) are said to have direct visibility of and access to all instruments and accessory controls. This is not entirely true, since in the mock-up the cabin air- conditioning and pressurization controls are mounted on a vertical panel at the co-pilot's elbow. Radio and autopilot controls are on top of the pedestal between the pilots, backed by the trim controls. Longitudinal trim switches are provided on both control wheels. The ultimate provision of an automatic landing system has been thought of, but Douglas give the impression that, since the system itself is not in sight, no one need worry too much about it. Rudder- pedal nosewheel steering enables both pilots to steer during takeoff and landing. Like the DC-8, the fuselage is of two-lobe design. The upper lobe has an outside diameter of 128in allowing four-abreast seating lor first-class passengers and five-abreast in the coach compartment. Douglas made a point of the fact that the ceiling height of 81ifl is 3in higher than the One-Eleven. The cross-section was chosen in order to increase below-floor cargo space and raise the ceiling. The single cabin entrance door swings downwards manually to
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