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Aviation History
1942
1942 - 1756.PDF
208 FLIGHT AUGUF-' 20TH, IQ42 ESTIMATING TAKE-OFF WEICHT-II Basic load=a + b + c + d = 3o,35o lb. As a percentage ol the basic load, 0 = 12.3 per cent.; 6=19.4 per cent. ; £ = 13.2 per cent.; and ^ = 55.1 per cent. From the table in Fig. 2, corresponding values for the above percentages are e = 48.65 ; / *= 48.2 ; g «= 47.45 ; and £ = 50.9. 48.65+ 48.2+ 47.45+ 50.9 .-. - 2_3 *" ^J J ^48.8 per cent. In this case basic load = 30,350 lb. =48.8 per cent, of take-off weight which calculated gives take-off weight = 62,190 lb. From intermediate curve in Fig. 1 lor basic FIG. IV t X 0 Hi u. fe- Ci t UJ BASI C OPERATIONA L EQUIPPE D WEIGH T TAR E WEIGH T P BON HEAVY BOMBER AIRCRAFT DISTRIBUTION OF WEIGHT ttl n- 10 STRUCTUR E POWE R PLAN T W1N6 S •1 P I LU a Li. WINGS COMPLETE ENGINE MTG. AND NACELLE STRUCTURE ENGINE AND NACELLE COWLINGS MAIN UNDERCARRIAGE UNIT TOTAL - WIN6 UNIT TAILPLANE AND ELEVATORS FIN AND RUDDER TOTAL - TAIL UNIT FUSELAGE TAILWHEEL UNIT TOTAL - FUSELAGE TOTAL - FLYING CONTROLS TOTAL FOR STRUCTURE WE R UNI T E T a -j in -t HI 3 ENGINES (DRY WEIGHT) AIRSCREWS (COMPLETE) ACCESSORIES TOTAL-POWtR UNIT (RADIALS) ^ FUEL TANKS (BABE- UNPROTECTED) FUEL SYSTEM OIL TANKS (BARE- UNPROTECTED) OIL SYSTEM TOTAL - FUEL SUPPLY UNIT TOTAL - POWER PLANT (RADIALS) TOlAl -BAPt WtlfiHT PROTECTION ANBL FIXED LOAD PROTECTION FIXED ARMAMENT > FIXED LOAD J TOTAL - TARE WEIGHT EMOVABLE LOAD REMOVABLE ARMAMENT i F!EMQVABLE EQUIPMENT > CREW > TOTAL -REMOVABLE LOAD TOTAL-BASIC OPERATIONAL EQUIPPED WEIGHT IBS, FUEL > OIL BOMBS'! FULL \ OIL J TAKE-OFF WEIGHT % TAKE OFF WEIGHT 30.000 5QpOO 11-9 2-6 1-8 3-9 20-4- • 1-0 045 1-45 10-6 0-35 1115 0-6 33-6 9-9 2-5 2-6 |5-0 2-0 0-5 0-15 0-85 3-5 IB-5 52 1 7-5 59-6 6-4 6-4 66-0 34-0 100-0 "/lone TO 70,000 12-85 2-5 1-0 4-45 Z08 1-22 0-43 1-65 8-4- 0-35 fi-75 0-6 31-8 11-2 2 8 3-9 17-9 1-24 0-46 0-2 0-45 235 20-25 52 1 9-5 61-6 6-4- 6-4 68-0 32-0 100-0 Fi?.. Average weight distribution as percentage of take off weight for bomber aircraft. Liquid Cooled Power Units. Heavy Bomber Aircraft Weight Distribution Power Unit— Engines (dry weight) Airscrews (complete) Radiator, cowling, liquid, system Accessories Total Power Unit (liquid cooled) % Take-off Weight Under 50,000 lb. 10.0 2.85 2.3 1.95 17.10 Over 50,000 lb. 10.2 2.9 2.4 2.5 18.0 load of 30,350 lb., take-off weight = 61,300 lb. Direct calculation should, of course, be the most accurate. As an example at the opposite end of the scale, a twin- engined bomber, assume from the specification the four known loads to be: (a) removable load = 4,ooo lb.; (b) two engines (dry weight) = 4,6oo lb. ; (c) bomb load=6,ooo lb.; (d) fuel and oil = 7,530 lb.; from which basic load = 22,130 lb., and as a percentage of the basic load, (a) = i8.i; (b) 20.8; (c) 27.1; and d) =34.0. Substituting repre sentation values from Fig. 2, e, f, g, h, respectively, wei 50.7 + 48.7 + 49.6 + 47.4 give =49-i per cent. V 4 Incidentally, this corresponds with the average load, and by direct reading from Fig. 2, take-off weight = 45,100 lb. for basic load as stated. Once the take-off weight has been established the weights can be distributed for each unit and component according to the chart in Fig. 3. Where the power unit is liquid-cooled, slight modification can be made by using the alternative in Fig. 4. It is possible in certain cases, where such loads as pro tective items or freed armament are above the average, that some slight adjustment may be necessary, but in any case the chart will assist materially in this respect. As with the fighter considered in the previous arflcle, it is recommended that once the weights have been dis tributed they should be issued to the drawing office so that during the detail design every cafe is taken that such estimates are not exceeded. Other data which may be of interest in connection with weight estimates for bomber aircraft are: — Average wing weight per sq. ft. of net area, but includ ing flaps and ailerons (50,000 to 70,000 lb. gross wt.) = 6.5 lb. per sq. ft. Fuel tank weights seem to vary per gallon capacity from 0.9 lb. for approx. 900 gallons total fuel capacity to 0.5 lb. for approx. 2,000 gallons total capacity. Oil tankage weight appears constant at 0.8 lb. per gallon capacity. A Wing loading varies from 38.0 to 48.0 lb./sq. ft. SpEr^ loading, 370 lb. to 700 lb. per foot span. Power loading varies from 10.0 to 15.5 lb. per h.p. nm 1 An •••BnBMMHHBBHHSBnHMmBHMi operation Hurricane of the R.A.F, about to drop a message at Zealand Division in Syria. exercises with a New
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