RT Journal Article
SR Electronic
T1 AERODYNAMICS OF GLIDING FLIGHT IN A HARRIS' HAWK, *PARABUTEO UNICINCTUS*
JF Journal of Experimental Biology
JO J. Exp. Biol.
FD The Company of Biologists Ltd
SP 469
OP 489
VO 149
IS 1
A1 TUCKER, VANCE A.
A1 HEINE, CARLTON
YR 1990
UL http://jeb.biologists.org/content/149/1/469.abstract
AB 1. A Harris' hawk with a mass of 0.702 kg and a maximum wing span of 1.02 m glided freely in a wind tunnel at air speeds between 6.1 and 16.2ms−1. The glide angle varied from 8.5% at the slowest speed to a minimum of 5% at speeds between 8.0 and 14.7 ms−1. The maximum ratio of lift to drag was 10.9 and the minimum sinking speed was 0.81ms−12. Wing span decreased when either air speed or glide angle increased. Wing area was a parabolic function of wing span3. Lift and profile drag coefficients of the wings fell in a polar area similar to that for a laggar falcon (Falco jugger) and a black vulture (Coragyps atratus). A single polar curve relating lift coefficients to minimum profile drag coefficients can predict the maximum gliding performance of all three birds when used with a mathematical model for gliding flight4. The parasite drag values that have been used with the model are probably too high. Thus, the profile drag coefficients determined from the polar curve mentioned above are too low, and the predicted wing spans for gliding at maximum performance are too large. The predicted curve for maximum gliding performance is relatively unaffected5. The maximum lift coefficient for the Harris' hawk in the wind tunnel was 1.6. This value is probably less than the maximum attainable, since the hawk's wings never appeared to stall. The best estimate of the minimum profile drag coefficient is 0.026 at a lift coefficient of 0.60.