Draft:Manual Reversion



Manual Reversion is the switchover from powered controls to manual control (primarily using cables and linkages) in adjusting the flight control surfaces through sheer muscle power from the pilot. This process is done as an emergency procedure in the event where most or all hydraulics have failed or are imminent to fail. While the term is mostly reserved for airplanes, helicopters may use a similar term in the case of a Governor Failure.

Manual Reversion requires a great amount of strength from the pilot as they are no longer assisted by power from batteries to raise or lower the control surfaces of the aircraft. Most aircraft included Manual Reversion modes prior when Fly-by-wire (FBW) became more widespread, with notable examples being the Boeing 737 and the A-10 Thunderbolt. However, the use of such systems became more obsolete as fly-by-wire underwent several improvements to its reliability. Today, very few modern aircraft have Manual Reversion modes.

History
Before the implementation of Manual Reversion, most airplanes lacked the option to switch to manual control due to the notion that triple-or-quadruple-string hydraulics would provide enough redundancy that a total hydraulic failure could never occur.