Optimized Engine out Procedures For Multi Engine Airplanes

Abstract

This investigation examined hazards associated with asymmetric thrust, engine out flying in twin engine airplanes at low speeds and low altitudes. National Transportation Safety Board (NTSB) data provided a measure of the comparative risks posed by control and performance inadequacies. Pilot training literature, as well as both pilot and instructor levels of awareness, indicated considerable misunderstanding of relevant aerodynamic principles. Virtually total emphasis has been devoted to directional control, which represents but one-third of the hazard. Regardless of circumstances, five degrees of bank is commonly believed to be the best available procedure for engine out flight. Mathematical analysis has been used to show that the optimum performance bank angle depends on several factors. In marginal rate of climb scenarios, the optimum bank is much smaller than five degrees. Wind tunnel experiments validated the analytical work and suggested substantially improved climb performance was achievable, with adequate control, by flying at zero sideslip. Flight tests in three light twin airplane models verified that angle of bank strongly influences rate of climb. Best climb resulted at the small angles of bank corresponding to zero sideslip. Increasing bank to five degrees degraded climb performance approximately 75-90 feet per minute from optimum. This penalty was equivalent to a weight addition of up to nine percent or a density altitude increase of as much as 1900 feet.