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Aviation History
1955
1955 - 0773.PDF
FLIGHT, 3 June 1955 •%• LOCKHEED v. DOUGLAS A Brief Comparative Analysis of Americas New Long-range Liners WE suggested in our issue of November 5th last that thenext generation of long-range airliners would be domi-nated by the Bristol Britannia and the various develop- ments of the Douglas DC-7. The great British turboprop liner is developing very satisfactorily, and it is not proposed to refer to it again here; but a new entrant has joined the race for global traffic, in the form of a Super-Super Constellation, the Lockheed L-1649. We now propose to draw a compari- son between this remarkable design and its similarly powered competitor, the DC-7C or Seven Seas. Incidentally, both types have been ordered in quantity, and soeach can be considered as a definite type to be reckoned with. Again, both represent the policy of "stretching" of a basic designcarried to what must be the ultimate degree. Both are powered by four Wright R-3350EA-2 Turbo-Compounds, giving 3,400 h.p.each up to 4,000ft and having a normal rated output of 2,800 b.h.p. to 4,300ft. Both L-1649 and DC-7C also have re-worked air-frames, with a revised tail assembly of rather greater area, and —more important—a new wing of longer span. These new wingshave higher aspect ratio, so induced drag figures are improved, and specific range likewise. The greater wing area is needed tocounteract the increased take-off weight; and the latter results largely from the immense tankages which the two new transportscan put into the extra space available inside the wing. Finally, most of the added span of both types has been inserted in thecentre section, so that the inboard engines are further out and the interior noise level is better than before. The new Lockheed, in particular, has a wholly new wing. Thesection is slimmer, the t/c ratio having been reduced from 18 to 15 per cent. The opportunity has also been taken to effect struc-tural improvements, and integrally stiffened skin is now used from root to tip on both lower and upper surfaces (previouslyonly the underside was so made). The chordwise spread of this integrally stiffened wing box is greater man before, so makingspace available for no less than 9,600 U.S. gallons. The tankage is entirely integral, all fuel lines being inside the tanks themselves.Other features of the 1649 are a new hydraulic system working at 3,000 lb/sq in, divided into two independent systems in parallel;a new and simplified twin-booster flying-control system; a wholly new flap system, with steel torque tubes driven by dual hydraulicmotors and screwing the flaps out on steel tracks; complete re-arrangement of the interior (which is again "styled by HenryDreyfuss") and heating of the lower freight holds to above 32 deg F at an outside air temperature of —20 deg F. Lockheeds have now worked out the performance of the 1649Aas accurately as they can at this stage, and they have compared it with the estimated figures for the DC-7C. Some of the resultsare given here, and we wish to stress that the figures are those assumed by Lockheed. The DC-7C performance does not, how-ever, differ materially from that put out by Douglas, and so can be accepted as accurate. In any case, no aircraft manufacturerwould deliberately falsify figures for a competitor's product; the airlines who are in the market for aircraft of this nature do theirown calculations. The outstanding characteristics of both the new transports arethe following: extreme range, either with maximum or reduced payload; block speeds only slightly better than those achieved BASIC COST ASSUMPTIONS ($1,0O0 = £357) Basic price C.F.E Galley Changes (based on experience) Radar Total Cost per engine Cost per airscrew Cost of radio Cost of airframe Weight empty Engine weight ... W.E., less engines Gross weight ... DC-7C $2,205,539 $40,000 $30,000 $20,000 $2,295,539 $79,800 $13,700 $45,000 $1,876,539 $1,976,339 73,238 Ib 3,609 Ib 58,802 Ib 139,000 1b 1649 A $2,295,000 $40,000 $15,000 $30,000 $20,000 $2,400,000 $79,800 $22,500 $45,000 $1,945,800 $2,080,800 85,752 Ib 3,609 Ib 71,316 1b 156,0001b A three-view drawing of the Lockheed L-1649 A with the shaded silhouette of the L-1049G Super Constellation in the plan view. Standard engine for both aircraft is the Wright Turbo-Compound. widi current equipment; a range of cruising altitudes "in theweather"; competitive direct operating costs; and a relatively low maximum payload, either reckoned on space- or weight-limitation.These are, in fact, all the hall-marks of a highly stretched design. If Lockheed and Douglas had started from scratch, using turbo-prop power, there is no doubt that they could have overcome their present deficiency in cruising speed, cruising altitude and maxi-mum payload. Reference to the curves of payload/range and range/block speedindicate (say Lockheed) the following results. In standard (62- passenger) form, the DC-7C will carry a payload of 17,050 lba distance (still-air, not an airline stage) of 4,010 statute miles. The 1649A will carry the same load a distance of 4,620 miles.The standard-configuration space payload of the DC-7C (17,550 Ib) can be carried 3,580 miles at maximum cruising power. Toincrease the distance, it is necessary to adopt 1-r cruise procedure OPERATING Basic empty weight Interior correction Empty weight ... Operating equipment: Crew and baggage .Life rafts Life vests Emergency radio Food, water, etc. Consumable oil Spares Total equipment weight Operating empty weight Space payioad Zero-fuel weight WEIGHT DETERMINATION L-1649A 62 seats 87,413 + 1,058 88,471 1,786 529 154 33 1,6531,741 88 6,041 94,569 11.111 105,680 L-1M9A 87 seats 87,413 0 87,413 1,786 661 198 33 1,9181,741 88 6,495 93,908 17.053 110,961 DC-7C 62 seats 75,001 0 75,001 1,786 529 154 33 1,6531,741 88 6,041 81,042 17,550 98,592 DC-7C 87 seats 75,001 -309 74,690 1,786661 198 33 1,9181,741 88 6,495 81,185 18,971* 100.156 * Limited by maximum landing weight.
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