Critical considerations for helicopters during runway takeoffs

This article presents optimal runway takeoff trajectories of a multiengine helicopter in the event of one engine failure. A point-mass model representative of the UH-60A helicopter is employed. Pilot response delays are ignored. Two optimal control problems are formulated for both continued takeoff and rejected takeoff after a single engine failure. Subject to specified safety conditions, the first formulation minimizes the runway length required for a given takeoff weight, whereas the second maximizes the takeoff weight for a given runway length in continued takeoff and for an unspecified runway length in rejected takeoff. Constraints on thrust angle, and thrust magnitude are included. For the continued takeoff, an optimal choice of the takeoff safety speed is determined to be about 15 ft/s above the initial airspeed at engine failure. Maximum takeoff weight is dictated by the remaining power after one engine failure if the runway length is sufficient, and is determined by the available runway length otherwise. For the rejected takeoff, the minimum runway length is a function of initial conditions at engine failure, and is roughly independent of takeoff weights. These results replicate some key characteristics of those from flight tests reported in the literature.