There were identified 11 aircraft accidents over a 22- year interval (between 1988 and 2009) involving stalls. American Airlines Flight 587 at Belle Harbor neighbourhood of Queens, N.Y., notorious Colgan Air Flight 3407 near Buffalo, N.Y., and Air France Flight 447’s plunge into the Atlantic Ocean were a few of the reasons asking for an immediate response in updating training procedures to prevent airplane upset as a cause of those accidents.
As a result to that, on August 6th, 2012, the FAA issued Advisory Circular (AC) Stall and Stick Pusher Training to provide best practices and guidance for training, testing, and checking for pilots to ensure correct and consistent responses to unexpected stall events and stick pusher activations. As a further response to improve pilot training FAA Issued Final Rule on Pilot Training on November 5th, 2013 which incorporates the following manoeuvres and procedures:
♦ Upset recovery manoeuvres
♦ Manually controlled slow flight
♦ Manually controlled loss of reliable airspeed
♦ Manually controlled instrument arrivals and departures
♦ Recovery from stall and stick pusher activation, if aircraft equipped.
♦ Recovery from bounced landing
Aircraft ‘upset’ is defined as an aeroplane unintentionally exceeding the parameters normally experienced in line operations or training. It is widely recognised that sometimes pilots are failing to avoid conditions that may lead to a stall, or failing to recognise the onset of an approach-to-stall during routine operations in both manual and automatic flight. Sometimes pilots may not have the necessary skills or competencies to appropriately respond to an unexpected stall or stick pusher event. Stall and approach-to-stall training should always emphasise reduction of the Angle of Attack (AOA) as the most important response when confronted with any stall event.
An upset is not necessarily a departure from controlled flight (i.e. a stall/spin) but it also includes abnormal attitudes and gross over/under-speed conditions. An upset can be caused by a number of things, either separately or together: There are several reasons such events occur
♦ Auto-Pilot or Auto-Thrust problems and failures.
♦ Miscalculated or wrong data entered into flight computers – giving rise to incorrect V speeds etc.
♦ Loss of flight augmentation systems – e.g. flap/slat failure.
♦ Loss of flight instruments e.g. after a bird strike or in severe icing.
♦ Environmental factors such as severe turbulence, Wake turbulence, Volcanic Ash or icing, especially at night.
♦ A lack of awareness, anticipation and/or attention by the pilots, possibly exacerbated by fatigue, illness or disorientation, poor monitoring, distraction or inaction.
♦ Inappropriate flying techniques and crew-monitoring, especially when hand- flying (e.g. during a manually-flown Go-Around) or after a stall/near-stall at high altitude with the AP engaged.
♦ Primary flight control problems.
♦ Equipment malfunction(s).
Investigation of pilot actions during these events suggest, that pilots involved in the accidents specialized in Level C or higher Level Full Flight Simulators. Although it is possible that some simulators that exist today may not have flight instruments, visual systems or other hardware needed to replicate the full six-degree-of-freedom movement of the airplane which may be required during unusual attitude training. It is important that the capabilities of each simulator be evaluated before attempting airplane upset training and that simulator hardware and software be confirmed as compatible with the training proposed.
Properly implemented equations of motion in modern simulators are generally valid through the full six-degree-of-freedom range of pitch, roll, and yaw angles. However, it is possible that some existing simulators may have equations of motion that have unacceptable singularities at 90, 180, 270, or 360 degree of roll or pitch angle. Each simulator to be used for airplane upset training must be confirmed to use equations of motion and math models (and associated data tables) that are valid for the full range of manoeuvres required. This confirmation may require coordination with the airplane and simulator manufacturer.
The importance of providing feedback to a pilot when control inputs would have exceeded airframe, physiological, or simulator model limits must be recognized and addressed. Some simulator operators have effectively used a simulator’s “crash” mode to indicate that limits have been exceeded. Others have chosen to turn the visual system red when given parameters have been exceeded. Simulator operators should work closely with training departments in selecting the most productive feedback method when selected parameters are exceeded.
Some part of Full Flight Simulators still may need significant updates to gain ability simulate Extended envelope conditions. And we are talking about issues like lack of airplane actual source data especially in non-normal flying conditions (severe Angle of Attack, too high or too low speed, excessive bank angle, dramatical manoeuvres in airplane stick or rudder) which demand more precise extrapolation to simulate those conditions. This leads to updating mathematical calculations in airframe physical response, airplane sub-systems and aerodynamics simulation. Other Full Flight Simulator systems will require updates as well: QTG tests, Motion and Control Loading systems movement forces replication. Estimated updates price can be as much, as 2.000.000 USD per simulator.