Safe autorotation through wind shear via backward reachable sets

Nicholas Grande, Shane Tierney, Joseph F. Horn, Jack W. Langelaan

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


This paper addresses the problem of safe flare to landing during autorotation, focusing on computing the region in the vehicle's state space from which a safe, feasible path to landing is guaranteed to exist. It (a) presents a method to compute safe, feasible trajectories for autorotation landing through wind shear and (b) uses this method to determine the set of conditions (distance to touchdown point, height above touchdown point, horizontal speed, descent rate, and rotor speed) from which a path to safe landing is guaranteed to exist. This set of safe initial states (denoted the safe landing set) is the backward reachable set from safe on ground to a steady-state autorotation condition. This safe set can be used by autonomous rotorcraft as a target condition for the steady-state phase of autorotation; it can be used in manned rotorcraft as a cue to begin flare. Safe landing sets are computed for two rotorcraft: the Bell OH-58A and a small electric-powered helicopter. The effect of wind and wind shear on the safe set is assessed for both vehicles. Finally, the feasibility of using global positioning system waypoint following control for autorotation landing is examined in simulation for the electric powered helicopter.

Original languageEnglish (US)
Article number022006
JournalJournal of the American Helicopter Society
Issue number2
StatePublished - Apr 2016

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Aerospace Engineering
  • Mechanics of Materials
  • Mechanical Engineering


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