FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1945
1945 - 0863.PDF
MAY 3RD, 1945 FLIGHT 479 aola ( THE author of this paper, which was read before the National Air Cargo Meeting of the Society of Automotive Engineers at Chicago, began his career as an aircraft designer in his native Czechoslovakia. He is now vice-president and chief engineer of Universal Moulded Products Corporation, of Bristol, Virginia. In the paper Mr. Nebesar makes an extensive study of the efficiencies of cargo aircraft design, and examines several designs for three different engine sizes and four different wing loadings. As a primary take-off requirement he uses Dr. E.P. Warner's formula, which specifies that the product of wing loading and power loading should equal 300. This is assumed for normal gross weight. For overload conditions a 20 per cent, overload is used. This brings the product of wing and power loadings to 432, which, the author considers, should still give a fair take-off performance on existing A-class airports. hold could be loaded 50 per cent, more than the other half. This would do away with lots of grief for the operators and would shorten the handling time considerably. ^ With these basic design features in mind, the basic parameters such as power loading and wing loading will now be investigated. For obvious reasons of simplicity and economy, it is believed that a twin-engine aircraft will be satisfactory for cargo operations for quite some time yet. Three different engine sizes have been selected, such as 1,200 take-off horse-power as the smallest engine to be used, 2,100 take-off horse-power as the medium size, and 3,500 take-ofjt. horse-power as the biggest engine. The pertaining horse-power of these engines will be 1,050 h.p. for the smallest, 1,800 h.p. for the medium, and 3,050 h.p. for the largest one. Around these engines, that is, around each of the above particular sizes, aircraft of different sizes and gross weights could be designed. Four sizes have been selected, that is, four different gross weights for each engine size and range from power loadings of 15 ib./T.O. h.p. to 7| lb./T.O. h.p., the intermediate powej; loadings being 11.5 and 9.1. The different designs are listed in the weight analysis— Table I, where, in line 6 the corresponding gross weights are given. For the lowest power loading, the gross weight will be only one-half of the gross weight of the aircraft, with the power loading as analysed. We have now twelve aircraft of designations, as given in line 1 of Table I, rang- ing from 18,000 1b. to 105,000 lb. gross weight. In order to satisfy the present take-off requirements and to have all these designs on the same basis in this respect, a foxmula proposed by Hon. E. P, Warner is used stating that the product of wing and power loadings should equal 300. This requirement gives us the wing loadings of 20 Ib./sq. ft., corresponding to 15 lb./T.O. h.p., and 40 lb./sq. ft. which corresponds to a 7.5 lb. power loading with the inter- mediate wing loadings being 26 and 33, as given in line 3 of Table I The pertaining wing areas are given in line 4. A twin-engined aircraft representative aspect ratio of 8.5, which determines the span values given in line 5, is assumed. The plan view taper ratio is assumed 3: 1 and frontal view taper ratio 6:1. Weight group statements established from different projects in a standard manner except for the pertaining notations are given in lines 7 to 13. Due to great variations of fuel tankage required, the weights of fuel tanks were included in the useful loads given in lines 18 and 19. Specific Wing Weights The .wing weights as given in line 9 are established from Fig. 1. This figure gives values of specific wing weights (in pounds per square foot of wing area) for different wing loadings and different gross weights, and were estimated partly from wing weights of actual aircraft, and partly from different projects. Since design speeds and, therefore, load factors will increase with increasing wing loadings (these corresponding to decreasing power loadings), it is evident that the specific wing weights for higher wing loadings will be greater. Of course, the specific wing weights will also 1 Airplane designation ... ... 2 Power loading W/T.O. h.p ". Wing loading W/S 4 Wing area, sq. ft. 5 Span, ft. A.R. 8J 0 Gross weight, Ib. ... ... \ 7 Power plant weight (including gas and oil 0k. installation, but excluding gas tanks), Ib.* "* 8 Nacelles (50 per cent, of weight assumed constant, remainder varying with wing chord) Ib . .. 0- Wing weight (from Fig. 2), lb 10 Tail surfaces (15 per cent, of wing weight), !b. 11 Body group (60 per cent, of weight assumed constant, remainder varying w'th wing chord), lb. ... 12 Landing gear (6.8 per cent, of gross weight), Ib. 13 Fixed equipment (difference only in de-icers, hydraulics and controls), Ib.** U Empty weight (excluding gas tanks), !b. ... I=L D .. Weight emptyli Ratio £ S—i percent. ... Gross weight .p D ,. Power plant weightIB Ratio ! —— per cent. ... * Weight empty t 17 ,. ,. Useful load Gross weight 18 Usefu' load (including gas tanks), lb 19 Useful load at 20 percent, overload, Ib. TABLE 1. 2X 1,050 Meto 2,400 T Al 15 20 1,800 123.5 36,000 4,700 580 0,250 940 2.350 2.450 2,900 20,170 56.0 23 3 44.0 15,830 23,030 A2 11.5 26 1,060 ' 95 27,600 4,500 510 3,600 540 2,100 1.880 2,250 15,380 55,7 29.2 44.3 12,220 17,740 -WEIGHT ANALYSIS H.P. Engines, . 0. H. P. A3 !).l 33 660 75 21,800 4,400 450 2,230 S35 1,900 1,480 2,100 12,895 59.1 33.8 411.9 8,905 13,265 A4 7.5 40 450 61.8 1S,000 4.300 410 1,520 228 1,750 1,220 2,050 11.478 63.7 37.4 3C.3 6,522 10,122 2x 1,800 Mete 4,200 T. Bl 15 20 3,150 163.5 63,000 8,800 1,930 12,900 1,935 4,500 4,280 4,400 38,745 01.5 22.7 S8.5 24,255 36,855 B2 11.5 26 1,860 125.5 48,300 8,500 1,670 7,520 1,130 4,000 8,280 3,600 29,700 61.5 28.6 38.5 18,600 23,260 H.P. Engines. 0. H. P. B3 9.1 33 1,158 99 38,200 8,200 1,500 4,630 695 3,600 2,600 3,000 24,225 63.4 33.8 36.6 13,975 21,615 B4 7.5 40 788 81.7 31,500 8,000 1,370 3,150 470 3.300 2,140 2,800 21,230 67.4 37.6 32.6 10,270 16,570 2x 3,050 Meto 7,000 T. Cl 15 20 5,250 211 105,000 14,400 4,550 24,900 3.750 8,050 7,150 6,700 69,500 6fi.2 20.7 33.8 35,500 50,500 . C2 11.5 26 3,090 162 80,500 14,000 3,950 14,500 2,175 7,200 5,480 5,000 52,305 65.0 20 8 35.0 28,195 44,295 H.P. Engine*, 0. H. P. C3 9.1 33 1,930 128 63,700 13,700 3,500 9,000 1,350 6,500 4,330 4,600 42,980 07.5 31.9 32.5 20,720 33,460 C4 7.5 40 1,313 105.5 52,500 13,500 3,200 6,150 925 6.000 3,570 3,85'J 37,195 70.8 36.3 29.2 15,305 25,805 * Deduction made for smaller *• Furnishings assumed 800 lb. diameter propellers, for A group, 1,400 lb. for B, 2,000 lb. for C.
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
