M.Sc Thesis

M.Sc StudentSegal Daniel
SubjectMax-Range Glides in Engine Cutoff Emergencies under
Severe Wind
DepartmentDepartment of Electrical and Computer Engineering
Supervisors PROF. Nahum Shimkin
PROF. Aharon Bar-Gill
Full Thesis textFull thesis text - English Version


Engine cutoff is a recurring emergency in General Aviation. It may be caused by an engine malfunction, fuel leak, improper aircraft maintenance or even a faulty fuel gauge. Such an event, coupled with adverse weather, may endanger passengers and crew. To tackle this event the pilot is required, in a very limited time, to evaluate reachable candidate landing sites for a given weather condition and to fly "correctly" - in a manner that minimizes aircraft energy loss rate. The objective of this work is to obtain max-range optimal trajectories that exploit to the utmost the airframe dynamic capability, accounting for intense in-plane and crosswinds. Such trajectories can be used to online evaluate the reachability of candidate landing sites and yield flight instruction to maximize the chances for a successful landing. In this work, we prove that the optimal trajectory in terms of minimal altitude loss must maintain constant heading and velocity. This result is obtained by first showing that the optimal height loss trajectory must maintain a constant velocity profile. This property allows reducing the altitude loss cost to the minimum time cost which is known as Zermelo's navigation problem. Furthermore, we derive a novel equation for the optimal glide velocity, whose solution depends only on the aircraft's optimal velocity in still air and the wind vector. We prove that this equation has a unique globally optimal solution, bounded by explicit lower and upper bounds. We show that the classical graphical technique to maximize the flight range, by employing the aircraft's glide polar in still air, can be generalized to include crosswinds. Last, we derive an explicit analytical expression for the optimal solution for strict crosswinds. We apply our results to Cessna 172 airframe, in realistic engine cutoff scenarios, including online landing site reachability evaluation.

Numerical simulations illustrate the performance improvement for a combination of severe tailwind and crosswind scenarios - compared to known results.