Analytical Criterion for Aircraft Spin Susceptibility

摘要

This paper presents an analytical criterion for spin susceptibility of airplanes based on the occurrence of a second SNB point at high angles of attack and large yaw rates signifying incipient spin. This approach is a significant departure from previous ones, which focused on either identifying low-α instabilities that may lead to spin onset or on explicitly seeking spin equilibria. Consequently, the analytical criterion could be obtained in a simple form, which is presented in two complementary ways: one, in terms of the zeros of a simple algebraic expression as a function of angle of attack, and alternatively as a composite plot of SNB points and accessible regions in r - α space. The composite plot simultaneously considers limits on all control deflections, identifies unconnected SNB points, and is likely to be more useful to the designer. The prediction by either form of the criterion is seen to match extremely well with spin onset observed in computations and in the spin tunnel for the F-18 HARV. The criterion needs to be tested against further sets of aircraft data; nevertheless, the present results are a significant achievement for the complex, longstanding and formidable problem of aircraft spin.