Upset recovery training: Lessons from accidents and incidents

Abstract

Loss-of-control upsets during normal flight are one of the most common types of aircraft accident. The study of these accidents reveals common characteristics that suggest areas where training can positively impact the safety of flight.

A variety of causes lead to in-flight upsets, including mechanical failures, wakes, spatial disorientation, and stalls. While most upsets occur fairly rapidly, those resulting from spatial disorientation often occur more slowly. Spatial disorientation upsets in roll have occurred when the flight crew was distracted or thought that the autopilot was on when it was off. Spatial disorientation accidents in pitch also have occurred due to the somatogravic pitch-up illusion. Upsets due to mechanical failure, wakes, and spatial disorientation most often occur at unstalled conditions well within the aerodynamic flight data envelope. However, improper responses can cause the aircraft to enter a stall after the initial upset or, if the initial upset was due to a stall, continue in a stall. Such improper responses include not putting the column forward enough, or pulling back even though this makes the situation worse. These responses may be due to an over-emphasis during training on recovering with ‘minimum loss of height’; hardly relevant where hitting the ground is not a problem. Nearer to the ground, improper responses could be due to the visual cue that has been called ‘ground rush’. At all altitudes, it is crucial to train pilots to reduce angle of attack as a primary part of upset recovery at, or near, stall.

Aircrews are likely to rely on stall protection systems to protect against loss-of-control upsets due to stalls. However, stalls due to airframe icing usually occur at a significantly lower angle-of-attack than stalls that occur with an uncontaminated airframe and, as a result, may occur before the stall protection system reaches the trigger angle-of-attack. Stalls may also occur without warning for uncontaminated airframes when the stall protection system fails. Such cases demonstrate the importance of recognising the stall cues and implementing positive sustained recovery controls promptly, without cues from the stall warning system. Even when the stall warning system does provide warnings, accident/incident history shows that crews may ignore stall warnings and either maintain nose-up controls or fail to execute and sustain positive recovery controls. Accident history also suggests that flight crews can be reluctant to move the pitch control in the nose-down direction when they are stalled and the aircraft is pitched nose low and/or significantly banked.

In each of these scenarios, training might prepare pilots to respond correctly. This paper will present short case studies of several aircraft upset accidents and incidents and explore common threads that suggest areas of training that could prevent future upset accidents and incidents.