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LSN24 Student Note Solution (Elliptical)

LSN24 Student Note Solution (Elliptical) - ME 387...

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Unformatted text preview: . ME 387, Introduction to Applied Aerodynamics Spring 2009 STUDENT NOTES AA-23 The Lockheed U-2R is a high altitude, long range, subsonic reconnaissance aircraft that takes advantage of a high aspect ratio planfon'n to efficiently produce lift. The following aircraft characteristics are noted: s=1occ n2 b=103®§® 1. The U-2 typically operates at altitudes in excess of 70,000 ft. Compute the dynamic pressure at 70,000 feet at maximum airspeed. If the U-2R were flying in SLS conditions, what flight velocity would create this same dynamic pressure? - — S : _ , 22E?) .mzfiifi micrometers W) I, . : a: crawl. W if add": 5.”: (isms-Fjj‘fl'riws‘s ifs): H15 migw “(79“.)”: awob‘tsj- a a . a a .51 c as fir“: VJ? : ”3%”: 1st,.“ 7“: gm: 5.30““? A) 77" . ,ucs _-—_" “0' _‘ M4 2. Pilots have claimed that high altitude flight in the U-ZR is panicularly difficult due to a very limited range of allowable airspeeds for level flight. At 0.8 Mach, the aircraft begins to experience buffeting due to compressibility effects and for airspeed of only 6 knots less, the aircraft Will begin to stall. This narrow band is commonly referred to as the “coffin corner” of the U-ZR's flight envelope. Assuming an elliptical lift distribution, calculate the induced drag at the lower limit of the “coffimmmefif r a weight of 38,1000 lb. (Answer: D; = 1070 lbf) CL: 3%]— W. C ... Eighties is) = C3 930(72 J” 3 L (i.3fi'rE:t)[-ra-t“191mm lot. it”. : "51sec ll, 5;. 1 _ iii/1. f” c .= sew? : 0.021.: 43: LETSLlE-‘l a 0,1. 't‘l' (10.51) 5: two ll“ R ' 1 V: .774.§Lfi/SI" L1(fi(%‘fl é): 7L 1'1 fi/S DE: Eff-A} 5 Cal: we 3. If the wing span (b) were shortened by 10% while still maintaining the same planforrn area (8), what would the new induced drag value? (Answer: Di = 1321.3 Lbf) .. ,e om _ (oflwfll CL— 0 3 1 AR‘ ”m? C06: (9.33%: :’o.o"5?.'7l We. 17 (5‘3” 3) _...__. __ . 1 d 0 , 4‘0331EF‘1DL'7L‘fr‘0Llucb)(emf-saw~-)':-' ((5521 Lu: L. E l ' “/9 harm-H- of” CL“) 1“. 39"] ”—1. 1“! 63 ’0 f, . [xx ,mldull J49 ...
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