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Aviation History
1932
1932 - 1235.PDF
DECEMBER 1, 1932 $5 THE AIRCRAFT ENGINEER SUPPLEMENT TO FLIGHT 50 45 40 55 30 25 a| X »- 20 15 10 5 0 3 - .—. ) FIG.7 PARTI 4 4 3j8^ ^ <j^ <&£ S Vs. < ^ ^ 3, V Y7 *\y A \ ^ P0IKT50F BEST ^,—- CLIMBIN6 SPEED ""j SHOWN THUS- Throttled curves ar design R.RM. 0 40 50 60 70 80 90 100 110 120 130 V m.p.h. 1000 900 s a u. 800 to S _J o fe 700 I 600 500 -f 7+* /? (^° 7.*^ K1 gg^. tfp>— FIG 8 PART 1 \. - 3 1000 2000 3000 4000 5000 DESIGN NORMAL R.PM 60 130 120 .c d. E > no 100 90 30 0 1000 2000 5000 4000 5000 6000 NORMAL R.P.M CRUISING about weight will not be out of place. No change in weight has been allowed for in any of the investiga tions, but when considering some specific case this has to be done. Not only is this due to fuel load and engine weight, but also to extra wing and structure weight for carrying the extra loads applied. Take for example Cases 1 and 5. The engine weight for Case 5 would be more than for Case 1, but the air screw would be lighter. The weight of the power plant without fuel tanks would be about the same in both cases. The fuel carried in Case 5 would be over twice that in Case 1. If a range of 400 miles is allowed then Case 5 will carry 19 gallons and Case 1 8.5 gallons, a difference in weight of 80 lb. in fuel alone. The struc ture difference would be about 20 lb., so that Case 1 would be 100 lb. lighter than Case 5. Another point which is worthy of attention is the tip speed in Case I, which is 1,175 f.p.m. No allowance is made for tip speed effect since the cases are purely illustrative and must be kept on a com parative basis. The piston speed also works out at something over 3,000 f.p.m., so that as an engine Case 5 is an impossi bility, but as a point on a curve it serves our purpose. REFERENCES. (1) "Light Aero Engine Development," Lieut-Col. L. F. R. Fell, 1 Pro ceedings," I.A.E., 1924—5. (2) " The Swing of the Pendulum," Editorial Comments, FLIGHT, October 13 1932. (3) " Aircooled Engine Power and Weight," W. R. Andrews, A.F.R.Ae.S., AIRCRAFT ENGINEER, July 24,1931. (4) "Notes on Airscrew-Bodv Interference," W. R. Andrews, AIRCRAFT ENGINEER, October 27,1932. (5) "The Estimation of Profile Drag," W. R. Andrews, AIRCRAFT ENGINEER, June 17, 1932. (To he continued.) NOTES ON THE USE OF STAINLESS STEEL IN AIRCRAFT STRUCTURES By H. J. POLLARD, Wh. Ex., A.F.R.Ae.Soc.* To the layman " stainless " steel has the unequivocal meaning implied by the word, that is, one and only one material that is stainless with the added characteristic of knife hardness. Actually "stainless steel" covers a wide range of different alloy steels, none of them absolutely stainless; some much more corrodible than others. Some of these steels are file-hard, others not much harder than lead. The phrase " stainless steel " is of such universal use that an attempt to supplant it by a more accurate descriptive name such as " corrosion-resistant " would be foredoomed to failure. We will therefore make no departure from the name standardised by long usage, but as the following notes show, it is not a question of describing a single material but groups of materials requiring more than 20 D.T.D. and B.E.S.A. specifica tions for aircraft structural use alone. How many times these specifications are multiplied when the re quirements of the cutler, ornamental architect, kitchen ware and household fitting manufacturer, motor engi neer, turbine, steam and petrol engine designer, chemi cal or mining engineer, etc., etc., are met, the writer has no means of knowing. The first requirement of the aircraft engineer is that by the substitution of stainless steels for the steels normally used, the structure shall not become heavier or less strong; also that the methods of construction and fabrication which have become standardised shall not require much modification for the new material. This latter consideration impeded the use of stainless steel in spars, ribs, etc., for years, as, with the strip available, strength and ductility could not be combined to a sufficient degree to enable the formation of small corrugations without cracking as in the case of the steels ordinarily used. In cases where sufficient * Mr. Pollard is in charge of metal construction at the Filton works of the Bristol Aeroplane Co., Ltd. 1152e
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