The European Aviation Safety Agency (EASA) issued recommendations regarding the training of pilots for unreliable airspeed indications at high altitude and the manual handling of the aircraft at high altitude.
This recommendation was issued following accidents and incidents, Air France flight 447 among others, in which the autopilot and autothrottle/autothrust disconnected following a loss of airspeed indication en route at high altitude. This led to a reversion to manual control and the temporary or permanent loss of control of the flightpath by the flight crew, particularly when operating close to the aircraft’s maximum operating altitude.
EASA strongly recommends that operators and training organisations of aeroplanes with max cruising altitude above FL300 provide pilots with briefing material, theoretical knowledge and practical training on the following elements, at the earliest possible opportunity and regularly thereafter, during their recurrent training.
EASA strongly recommends that the same elements are included, by ATOs, in initial type rating training for the same category of aeroplanes.
- Basic flight physics principles concerning flight at high altitude, with a particular emphasis on the relative proximity of the critical Mach number and the stall, pitch behaviour, and an understanding of the reduced stall angle of attack when compared with low altitude flight (see EASA SIB 2015-07).
- Interaction of the automation (AP, FD, ATHR) and the consequences of failures inducing disconnection of the automation.
- Consequences of an unreliable airspeed indication at high altitudes and the need for the flight crew to promptly identify the failure and react with appropriate (minimal) control inputs to keep the aircraft in a safe envelope.
- Degradation of FBW flight control laws/modes and its consequence on aircraft stability and flight envelope protections, including stall warnings.
- Practical training, using appropriate simulators, on manual handling at high altitude for all pilots in normal and in non-normal flight control laws/modes, with particular emphasis on pre-stall buffet, the reduced stall angle of attack when compared with low altitude flight and the effect of pitch inputs on the aircraft trajectory and energy state.
- The requirement to promptly and accurately apply the stall recovery procedure, as provided by the aircraft manufacturer, at the first indication of an impending stall.
- Procedures for taking over and transfer manual control of the aircraft, especially for FBW aeroplanes with independent side-sticks.
- Task sharing and crew coordination in high workload/stress conditions with appropriate call-out and acknowledgement to confirm changes to the aircraft flight control law/mode.
- EASA SIB No.: 2015-17 (PDF)