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Aviation History
1929
1929 - 1346.PDF
SUPPLEMENT yo PLIGHT JUNE 27, 1929THE AIRCRAFT ENGINEER i' 6 J. TTTT : 111 ( TTTT 111! ,,,, TTTT \ \ \ \ 1 TTTT V Vv \ TTTT ... TTTT -TTTT TTTT FIYING-BOAT / -—— -• - ~-* V—, TTTT Till HULL ^^ TTTT TTTT FIG.I. <^ TTTT TTTr *" •. TWIN SEAPLANE FLOATS MM i 111 1111 i 11 i TTIT. : \ : : ; : j ; l|ir - O 20 30 40 50 60 70 80 SPEED AS '/% OF TAKE-OFT SPEED ZSrjTTT £20 3 30 °0 I I I I I 1111 |l I M [ I 1111 I M I 11 11 I 111 11111 M I 11II I I I IIII 11111 FLYING-BOAT HULL FI6.2 TMN SEAPLANE FLOATS Ns K'MV+C- 3O40S0 60 70 8O SPEED AS % OF TAKE-OFF SPEED miiiiniiiin "^ If the lift of the planes be assumed proportional to Taking then as previously the " load on water" [at (speed)1, then the " load on water " (L) at any speed V is speed V to be given by Vs \ L = T *• ' we have L_ ™ l-y R~^~ „./V "< •where W = at-rest displacement (all-up weight of machine) Vo = take-off speed. rr 1 • .L i- load on waterTaking the ratio : = /resistance then / = - c _ V*' dV V.M V\mV + c ) + c) (-2V)-»(V,»- tiso (mV + c)1 J = - W f wV» + mY08 + 2cV ) V\ (mV + c)» J f(mV + cf (2mV + 2c) -= ~_J (mV» + «V 8' + 2cV)(mV + c) (2m) (wiV + c)1 And while d/' = 1 / - 2V0 when V = V, (2) _ ~ 1L\2 (c*" 2W ""v7\(mV+ «)•• _ 2W|maV01 SI + c)3J when V = Vo Substituting c = KV9 d*f 2W The expression in equation (2) is a positive) quantity, showing that if the resistance curve follows the law / V V2 x L R = gW I — —-), then the —- curve approaches zero as the take-off speed is reached. Flying-boat hulls are more efficient than twin seaplane floats for the major portion of the speed range during the take-off run, and it would appear that if, with the former type, the resistance curve beyond the " hump " speed can be made to approximate to a straight line law, an additional advantage will be obtained. KV0 _ 2W \( m K) It is clear that the slope of the straight line resistance •curve gives a negative value for " TO," with the result that the «xpression in equation (1) is also negative, showing that the —JJcurve in this case approaches infinity as the take-off speed THE TAIL PLANE AREA TO GIVE LONGITUDINAL STABILITY. [[By W. R. ANDREWS, Higher National Diploma (Hons.), Many attempts have been made to express in a convenient formula the size of tail plane to give longitudinal stability. Consistent results cannot be expected from a formula l h f thpwhich takes into account only the moment of area, as the l l R In " An'Investigation into the Take-off of Flying Boats," aerodynamic properties of the main planes and tai plane by A/ Gouge, B Sc, A.F.R.Ae.S. (FLIGHT ENGINEERING Play an 6?uaUy important part. SUPPLEMENT! November 24, 1927), it was shown that Bv "fPS f few Justxfiab e assumptaons one can amyethe water resistance curve in the case of flying-boat hulls a* a gently accurate relationship of the tail area to approximated to the law e g^metry of the aircraft and the non-dimensional co-rr — — . .. efficients representing the aerodynamic qualities. Between the stable and the unstable region is one known as " neutrally stable." In this region a large speed range where q = a constant depending on the hull shape. is possible without necessitating a change of trim. 522/
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