A Study of Flap Management, an Analysis of the Consequences of Flap Management, and a Search for Possible Causes

Abstract

An exploration of current aviation education as to the purpose, aerodynamic theory, and proper usage of high lift devices, particularly trailing-edge 'wing flaps, was conducted. Aircraft accident data involving the mismanagement of the wing flaps as a cause/factor were analyzed and typical accidents were studied. The accident data show that a relatively high number of flap-related accidents occur and with dangerous consequences. Flight tests were conducted to recreate certain conditions of flight reported in the accident data. T~e following paper presents an in-depth explanation of the purpose, the aerodynamic theory, and the aircraft performance related to the proper usage of wing flaps. Additional data relative to the dangers of flight safety associated with the incorrect use of wing flaps is included. This study was primarily concerned with single-engine and twin-engine airplanes used for flight training. INTRODUCTION During the preparation of lectures for a course in basic aerodynamics, a number of aviation textbooks and flight manuals were studied for material concerning the management of wing flaps. It was observed that there is no consistency in how the various aspects of wing flaps are explained. In some flight training manuals and textbooks, there are statements of the purpose of flaps and descriptions of the different types of flaps available, while in other textbooks there are explanations of the changes in the coefficients of lift and drag caused by the extension and retraction of wing flaps. In pilot operating handbooks, instructions for the use of flaps are brief statements of what amount of flaps to use for takeoffs and landings. However, these handbooks generally do not explain the reasons for a particular flap setting or restriction. As a consequence, an investigation was begun of the purpose of wing flaps, the aerodynamic theory of wing flaps, the procedures for the use of wing flaps, and the reports of flap-related accidents.