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Several aviation incidents and accidents have occurred in which the control surfaces of the aircraft became disabled, often due to failure of hydraulic systems or the flight control system. Other incidents have occurred where controls were not functioning correctly prior to take-off, either due to maintenance or pilot error, and controls can become inoperative from extreme weather conditions. Aircraft are not designed to be flown in such circumstances, however a small number of pilots have had some success in flying and landing aircraft with disabled controls. ==Control techniques== A basic means of controlling an aircraft with disabled flight controls, discovered through crew experience, is by making use of the position of the engines. If the engines are mounted under the centre of gravity, as is the case in most passenger jets, then increasing the thrust will raise the nose, while decreasing the thrust will lower it. This control method may call for control inputs that go against the pilot's instinct: when the aircraft is in a dive, adding thrust will raise the nose and vice versa. Additionally, asymmetrical thrust has been used for directional control: if the left engine is idled and power is increased on the right side this will result in a yaw to the left, and vice versa. If throttle settings allow the throttles to be shifted without affecting the total amount of power, then yaw control can be combined with pitch control. If the aircraft is yawing, then the wing on the outside of this yaw movement will go faster than the inner wing. This creates higher lift on the faster wing, resulting in a rolling movement, which helps to make a turn. Controlling airspeed has been shown to be very difficult with engine control only, often resulting in a fast landing. A faster than normal landing also results when the flaps can not be extended due to loss of hydraulics. Another challenge for pilots who are forced to fly an aircraft without functioning control surfaces is to avoid the phugoid instability mode (a cycle in which the aircraft repeatedly climbs and then dives), which requires careful use of the throttle. Because this type of aircraft control is difficult for humans to achieve, researchers have attempted to integrate this control ability into the computers of fly-by-wire aircraft. Early attempts to add the ability to real aircraft were not very successful, the software having been based on experiments conducted in flight simulators where jet engines are usually modelled as "perfect" devices with exactly the same thrust on each engine, a linear relationship between throttle setting and thrust, and instantaneous response to input. More modern computer systems have been updated to account for these factors, and aircraft have been successfully flown with this software installed. However, it remains a rarity on commercial aircraft. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Flight with disabled controls」の詳細全文を読む スポンサード リンク
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