A post in the thread causes myself to go back to the upset and stall and the
unsuccessful recognition and recovery from the stall.
Upset recovery training zip
posted on
http://www.pprune.org/tech-log/41797...ml#post6652672
Although the posted reference is dated from August 2004, it is imho an excellent work. It is not the powerpoint presntation, but it consists of 185 pages of very interesting read.
But it deals with non FBW aircraft, has some references to them that those might not stall as being protected.
Actually if those informations and recomendations had been used from the crew of AF447, the outcome would have been most probably a different one.
I´ve copied some sentences for info.
Simulator versus reality
There are issues associated with differences between simulator training and aircraft recoveries. A simulator can provide the basic fundamentals for upset recovery, but some realities such as positive or negative g’s, startle factor, and environmental conditions are difficult or impossible to replicate. These limitations in simulation add a degree of complexity to recovery from an actual aircraft upset because the encounter can be significantly different from that experienced during simulator training. Therefore memory checklists or procedural responses performed in training may not be repeatable during an actual upset situation. The limitations of simulators at the edges of the flight envelope can also cause fidelity issues because the simulator recovery may or may not have the same response characteristics as the aircraft being flown. However, provided the alpha and beta limits are not exceeded, the initial otion responses and instrument indications of the simulator should replicate airplane responses.
The Alpha and Beta values are depicted in Appendix 3 for a lot of aircraft, from AB the A300/A310.
In short with flaps up flight validated from 0° AOA up to 12 AOA,
Wind tunnel / analythical from -5°AOA up to 12 ° AOA
Extrapolated for simulator from -5° AOA up to 30° AOA
AF447 maneuvered well outside those limits.
Startle factor
It has already been stated that airplane upsets do not occur very often and that there are multiple causes for these unpredictable events. Therefore, pilots are usually surprised or startled when an upset occurs. There can be a tendency for pilots to react before analyzing what is happening or to fixate on one indication and fail to properly diagnose the situation. Proper and sufficient training is the best solution for overcoming the startle factor. The pilot must overcome the surprise and quickly shift into analysis of what the airplane is doing and then implement the proper recovery. Gain control of the airplane and then determine and eliminate the cause of the upset.
Unloading
Airline pilots are normally uncomfortable with aggressively unloading the g forces on a large passenger airplane. They habitually work hard at being very smooth with the controls and keeping a positive 1-g force to ensure flight attendant and passenger comfort and safety. Therefore, they must overcome this inhibition when faced with having to quickly and sometimes aggressively unload the airplane to less than 1 g by pushing down elevator.
Cockpit environment
Pilots must anticipate a significantly different cockpit environment during less-than-1-g situations. They may be floating up against the seat belts and shoulder harnesses. It may be difficult to reach or use rudder pedals if they are not properly adjusted. Unsecured items such as flight kits, approach plates, or lunch trays may be flying around the cockpit. These are things that the pilot must be prepared for when recovering from an upset that involves forces less than 1-g flight.
Flight controls
Utilizing full flight control authority is not a part of routine airline flying. Pilots must be prepared to use full flight control authority if the situation warrants it. In normal conditions, flight control inputs become more effective with increased speed/ reduced angle of attack. Conversely, at speeds approaching the critical angle of attack, larger control inputs are needed for given aircraft reactions. Moreover, during certain abnormal situations (partial high lift devices, thrust reverser in flight) large or full-scale control inputs may be required. Attitude and flight path changes can be very rapid during an upset and in responding to these sorts of upset conditions, large control inputs may be necessary. It is important to guard against control reversals. There is no situation that will require rapid full-scale control deflections from one side to the other.
Stall aproach / Stall
Pilots are routinely trained to recover from approach to stalls. The recovery usually requires an increase in thrust and a relatively small reduction in pitch attitude. Therefore, it may be counterintuitive to use greater unloading control forces or to reduce thrust when recovering from a high angle of attack, especially at lower altitudes. If the airplane is stalled while already in a nosedown attitude, the pilot must still push the nose down in order to reduce the angle of attack. Altitude cannot be maintained and should be of secondary importance.
Stall recovery
A stall is an out-of-control condition, but it is recoverable. To recover from the stall, angle of attack must be reduced below the stalling angle—apply nosedown pitch control and maintain it until stall recovery. Under certain conditions, on airplanes with underwing-mounted engines, it may be necessary to reduce thrust to prevent the angle of attack from continuing to increase. If the airplane is stalled, it is necessary to first recover from the stalled condition before initiating upset recovery techniques.
Stall recovery procedure for AF447 (would have worked, imho)
Situation: Pitch attitude unintentionally more than
25 deg, nose high, and increasing.
Airspeed decreasing rapidly.
Ability to maneuver decreasing.
Nose-high, wings-level recovery:
◆ Recognize and confirm the situation.
◆ Disengage autopilot and autothrottle.
◆ Apply as much as full nosedown elevator.
◆ Use appropriate techniques:
• Roll to obtain a nosedown pitch rate.
• Reduce thrust (underwing-mounted engines).
◆ Complete the recovery:
• Approaching horizon, roll to wings level.
• Check airspeed, adjust thrust.
• Establish pitch attitude.
Pitch control
Pitch may be controlled by rolling the airplane to a bank angle that starts the nose down. The angle of bank should not normally exceed approximately 60 deg. Continuous nosedown elevator pressure will keep the wing angle of attack as low as possible, which will make the normal roll controls effective. With airspeed as low as the onset of the stick shaker, or lower, up to full deflection of the ailerons and spoilers can be used. The rolling maneuver changes the pitch rate into a turning maneuver, allowing the pitch to decrease.
An interesting read, especially IMHO for the non-flyers on this thread. Pilots should know it anyway.