THE USE AND MISUSE OF MATHEMATICAL FLIGHT MODELS

ABSTRACT

There are two types of mathematical flight models. A particular model is constructed by an observer or experimenter to describe observations of a particular animal in particular circumstances, and may include any amount of detail about wing kinematics, vortex wake structure, etc., provided that such details have been observed. The detailed results apply only to the particular animal observed. A general model attempts to predict certain aspects of performance for any flying animal, based on estimates of body mass, wingspan, wing area, and very little else. This calls for simplified methods of calculation. It is not possible to improve the accuracy by introducing additional details, because such details are unknown for most species. Confidence in the predictions of a general model depends on feeding back field observations, and trying to eliminate discrepancies by adjusting variables whose values are only roughly known or guessed. The computer programs by Pennycuick (1989b, Bird Flight Performance, Oxford Univ. Press) were designed to facilitate this process, and are recommended for the use of field observers.