320 AIRCRAFT ENGINEERING December, 1931 statemen t is also true. Any comparison which (2) Rigid feathering blades generate high lift applies to aerofoils tested statically remains valid withou t excess of weight, vibration, or gyroscopic A New Gyroplane when these aerofoils are used as blades of an auto- action . rotativ e system. That is, a high lift aerofoil used (Concluded from page 306) (3) Rotor control combined with stub wing a s a blade section of a gyroplane will give high produce s lateral balance in vertical descent and TABLE VI lift values for the gyroplane, or, highest L/D for landing in bad wind conditions on rough ground. sections when used in this manner produce highest Angle of (4) Simplicity of structure means low cost pro Attac k K K L/ D on the gyroplane. K y m L duction and maintenance. I t is interesting also to note that the blade with I n our actual flight tests and wind tunnel tests, 2-in . b y 21-in . blade s th e largest c.p. trave l produces th e greates t moments th e extreme smoothness of the rotor in starting, 15 .. 0·00171 .. -0·000008 .. 0·000039 for the gyroplane system. This effect is of academic 20 .. 0·00218 .. -0·000023 .. 0·000049 flying, and decelerating has been noticed. This 25 .. 0·00259 .. -0·0000045 .. 0·000060 interes t mainly, as all moments measured can be opens up the possibility of carrying the majority 30 .. 0·00287 .. -0·000010 .. 0·000071 take n care of easily b y conventional tail surfaces. of the weight of the plane on the stub wing at 3-in . b y 21-in . blade s cruising speed, which will allow the rotor to slow 15 .. 0·00194 .. -0·000035 .. 0·0000337 TABL E V 20 .. 0·00263 .. -0·000029 .. 0·0000493 down in level flight thus decreasing the drag and 2 5 .. 0·00307 .. -0·000024 .. 0·0000650 increasing the speed range of the machine. R.A.F . 34 U.S.A . 35-B 0·00317 .. -0·000019 .. 0·0000800 30 .. 3-in. by 2-in. by 21-in. blades TABLE VII Max, K (L/D)2 .. .. .. 0·012 0·462 0·00188 15 .. 20 .. 0·00267 Max . K max .. .. . .. 0·00270 0·00313 Model Reference Velocity 25 . 0·00322 K min. .. .. . .. 0·000030 0·0000512 30 .. 0·00330 Max. thickness .. .. . 12·64 % .. 12·00% Wilfor d gyroplane-four 2 in . N.Y.U . Tunnel Max . mea n camber .. .. 2·0 % 5·0 % is even greater than that obtained by tapering b y 21-in. blades, 48-in. Test No. 529 Zero lift angle .. .. .. -1 deg. -5·4 deg . diamete r rotor aerofoil on the conventional aeroplane. (a) R.A.F.-34 blades 2 deg . 30 m.p.h. 0·00280 Th e K value of 0·00330 referred to disc area A series of tests were made on three sets of incidenc e 15deg. sweep- which was obtained with th e tapered blades is the back , no dihedral blades with the U.S.A. 35-B aerofoil:— (b) R.A.F.-34 blades 0 deg . 30 m.p.h. 0·00260 highest coefficient for lift ever obtained in this (1) 2-in. chord , 21-in. span . incidence 15 deg. sweep- wind tunnel or any gyroplane, and, as far as we (2) 3-in. chord , 21-in. span . back , 5 deg . dihedra l know, it is the highest ever obtained in a wind (c) U.S.A. 35-B blades 0 deg . 30 m.p.h. 0·00302 (3) 3-in. root chord, 2-in. ti p chord, 21-in. span. incidenc e 15 deg . sweep- tunne l test for a rotating aerofoil system. I n this scries of tests the angle of incidence was back , no dihedral Tabl e VII gives values of maximum K kep t constant at 0 deg., the sweepback at 15 deg., (d) U.S.A. 35-B blades 30 m.p.h. 0·00330 obtaine d on various aerofoil systems:— 0 deg . incidence 15 deg . an d the dihedral a t 0 deg. sweepback , n o dihedra l Coefficients were taken at the position for take Th e results of the solidity tests are briefly as off, coefficients in vertical descent being consi follows: — (2) La Cierva type autogiro British R. & M. 100 ft./sec . 0·00206 derabl y higher. The coefficient of drag in vertical (1) The increase in chord of the rectangular 6 ft. diamete r 3 deg . inci - 1154 denc e (four blades) descent, i.e., with the plane of rotation a t 90 deg. blades from 2 in. to 3 in . increased the lift of the (3) La Cierva type auto- Göttingen Test 0·00187 t o the wind, was found to be 0·0032 lb./sq. ft. of system . giro, 23½-in. diameter, disc area per m.p.h. (2) The tapering of the blades from 3 in. a t the blad e incidence -2 deg. (four blades) Th e main differences between a gyroplane and root to 2 in . a t th e tip increased the lift when com (4) La Cierva type auto- NY.U. Tunnel 0·00172 othe r types of aircraft are :— pare d with either the 3-in. rectangular or the giro , 4-ft. diameter , three Student thesis (1) Small span of rotor is mad e possible through 2-in. rectangular blades. blades , incidence -3 deg . work (unpublished) high r.p.m. and high lift aerofoil. Th e advantag e gained from tapering these blades
Aircraft Engineering and Aerospace Technology – Emerald Publishing
Published: Dec 1, 1931
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