Loss of Control In-Flight (LOC-I)
The aircraft departs from normal controlled flight: a stall, an upset, or a control problem the crew cannot recover from.
Loss of control covers everything from an aerodynamic stall to an unrecoverable upset following an autopilot disconnect, an icing encounter, a mistrimmed stabiliser or a failed flight-control component.
It is now the leading cause of fatal accidents in commercial aviation, and its investigations usually turn on two questions: what put the aircraft outside its normal envelope, and why the recovery did not work. The second question is frequently about training, startle and what the instruments were telling the crew.
Related terms
An airworthy aircraft, under the crew's control, is flown into ground, water or an obstacle, usually because nobody on the flight deck knew the terrain was there.
The aircraft told the crew something untrue: blocked pitot tubes, a failed angle-of-attack vane, or disagreeing airspeed and altitude indications.
Crew Resource Management: how a flight deck uses all the people and information available to it. CRM breakdowns are about communication, workload and authority, not stick-and-rudder skill.