Recovery to powered flight

Ultimately any autorotation that does not result in an engine-off landing will require a recovery to powered flight. The aircraft characteristics during this phase of flight will be heavily dependent on the engine and rotor governing system. Any tendency of the engine to surge as the throttle is advanced or as the collective is raised will clearly add to the difficulty of the manoeuvre. Of particular interest is the height loss involved during the recovery, as this will affect the usefulness of the aircraft in performing realistic practice forced landing (PFL) profiles. The cross-coupling associated with rapid recoveries to powered flight may be significant and will give an idea of the difficulties that may be encountered during the engine-off landing phase. Tests com­mence at a safe altitude with recoveries from flight idle glide. It should be remembered that the recovery from flight idle glide is a common operational manoeuvre following rapid descents and not just associated with a temporary power loss.

7.6.4.3 Entry into autorotation

Once the aircraft characteristics in steady autorotation have been investigated, rapid entries into autorotative flight are evaluated. These tests should start with gentle entries into flight idle glide (throttle(s) in the flight position) and then progress incrementally onto rapid entries into autorotation (throttle(s) retarded). Tests are conducted closed loop and are made initially at VMP in level flight. Eventually the full speed range is checked in addition to climbing and descending flight. Information is gathered on the control movements required to counter the cross-coupling effects associated with rapid collective lever lowering. An assessment is also made of the adequacy of the remaining control margin to cater with more aggressive entries perhaps associated with a surprised operational pilot who is not expecting a total power failure! The margins available in steady autorotation will already be known but the dynamic situation of rapid entries can create problems with the aft cyclic margin (particularly at high speeds) and the pedal margin (particularly at low speeds). The transient overswing properties of the rotor governing system are also important for FIG entries especially if the pilot is required to raise the collective lever again to control a rapid increase in rotor speed. Once experience has been gained of rapid entries with the pitch attitude held constant further tests are conducted to investigate entries with a nose-up flare simulating the high-speed/low-level engine failure recovery actions.

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