Stalled Airplane - The FAA announced rules in 2013 aimed at upgrading airline pilot training. The amended rules, which have been under review for several years, focus on eliminating the type of parking accidents and pilot behaviors that occurred in two fatal high-visibility accidents in 2009. In both crashes of Air France 447, with an Airbus A330 traveling between Brazil and France, and in the crash of Colgan 3407, a turboprop airplane that crashed outside of Buffalo, New York, the pilots unexpectedly applied reverse pressure flight control keeping the aircraft in an extended stall.
Although it is easy to blame the pilots involved in these situations, when we see similar actions involved in these and other scenarios, we must carefully consider whether or not there is a systemic problem. If it is, there may be a greater risk if similar actions take place in the future.
Stalled Airplane
Although all pilots are taught from the early stages of their career that in a stall emergency they should lower the nose to reduce the angle of attack, when pilots reach the point in their career where they are flying larger aircraft with higher performance, they are often Learned something completely different from this. For decades, the practical test standards for commercial and airline pilots used minimum altitude loss as the criterion by which pilots were judged. Since "minimum" is a rather vague term, in many training cases, an attempt is made to quantify the term "minimum". In the case of many aircraft with significant excess thrust at lower altitudes, it is possible to recover from the first stall indication without any loss of altitude.
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Although this provided an objective measure for evaluating pilot performance, it was the wrong parameter to measure. The greatest threat to a stalled aircraft is not always loss of altitude. A much greater threat in general is a pilot's loss of control after an unexpected stall encounter. The problem with the minimum height loss standard is that it promotes exactly the wrong behavior in a stall event. In order to minimize altitude loss, the pilot may feel the need to maintain or even increase back pressure on the flight controls, rather than releasing back pressure as is often required to decrease the angle of attack. Thus, in our pursuit of objective assessment, we have trained a generation of Airmen to practice techniques that could be detrimental to their safety in front of a stall.
While the pilots of Air France 447 and Colgan 3407 were never taught to act in the manner they demonstrated in their accidents, they were indeed trained in one aspect of their behavior, to keep pushing to minimize attitude loss.
Regulations are changing to require simulators to accurately represent aircraft behavior up to full aerodynamic stall in the future. Moving from the current policy of recovering only from initial indications or warnings of a stall to teaching pilots how to recover from a full stall requires simulator improvements. The FAA allowed five years to make the necessary simulator modifications. There is another way.
Because proper stall recovery technique is rarely aircraft specific, it is possible to train for a full stall recovery in an aircraft that may be different from a transport class airline aircraft, which is certainly not designed for safety in the stall training regime. There is another element that is important in training for stalls and other disruptive events in a real aircraft as opposed to a simulator: the psychology of reality. Pilots must learn to manage the surprise response to an unexpected rollover of the aircraft. No matter how realistic the simulator, there is a different psychological dynamic involved in real flight than in the virtual world.
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Both full flight simulators and in-flight training have limitations and advantages. This is why the most comprehensive solution to stall training involves the complementary and integrated use of both training resources to most effectively train pilots in proper stall response and recovery techniques. Although the orders announced by the FAA do not require changes to aircraft training, at APS we use both aircraft and flight simulators as training platforms in combination to provide the best overall obstacle prevention and recovery training available in the world today.
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In principle, commercial aircraft do not just crash, even at low speeds. They are designed in such a way that they have been lifted even at speeds of only 280 kilometers per hour. The lift is caused by the special shape of the wing. The wing deflects the air down and thus creates its own lift.
This works well as long as the air flows cleanly back over the blade surface. In the area of the rear wing, a larger volume of air is created and therefore negative pressure, which essentially pulls the wing up.
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But this only works if the wing is at the correct angle of attack with the surrounding air. If the angle becomes too steep (above about 15 degrees), the streamlines at the trailing edge of the wing will separate from the wing surface. Vortices are created. This is already a first warning sign.
It gets even worse if the pilot does not intervene. He must push down the nose of the plane to reduce the angle of attack. In this way it avoids eddies and can ensure lift. If it does not do this and the aircraft becomes steeper and steeper in the air, a dangerous stall occurs, starting at about 18-20 degrees angle of attack. This means that the air over the entire wing begins to rotate.
The wing loses lift and thus its entire function. The plane pitches forward and goes into the cup. When the plane flies in curves, the stall can also occur on only one wing. The plane then starts to spin and falls like a rock. Only at very high altitude can experienced pilots manage to regain control of such a falling plane.
Especially when climbing, such situations almost always result in a crash. Commercial aircraft are most often involved in accidents during this phase of flight. The slower an aircraft flies, the greater the angle of attack must be for the aircraft to gain enough lift. If it does not reach the required stall speed, a stall occurs.
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Shortly after takeoff, an aircraft needs significant thrust to simultaneously increase its speed and gain altitude. If the thrust is reduced during the climb, this inevitably leads to a significant loss of speed.
In any case, it is important for pilots to know their airspeed and angle of attack of the wing. If the sensor providing the data is faulty, pilots must switch to a backup sensor. However, they must also be able to identify which of the two sensors is faulty. If they now rely on the faulty sensor, this quickly leads to disaster.
The black box of Air France flight 447 was found at the bottom of the Atlantic Ocean. Image: Image alliance/dpa
In three flight accidents in the last decade, a police speed measurement with the so-called pitot tube was the cause of the crash: Birgenair Flight 301 crashed in 1996 on approach to the Dominican Republic. Dust collected in the speedometer tube. A very similar reason was found in the crash of Aeropuerto Flight 603 in the same year. Except the pipe wasn't dirty there, but it was plugged as a precaution. The problem was that no one had removed the tapes before the start.
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In both cases, the pitot tube signaled to the pilots a speed that was too high. In the case of the Birgenair flight, the pilot tried to deal with this by pulling the nose of the aircraft - a disastrous mistake. The pilot ignores the correct data from a second sensor and an impending stall warning signal because he is probably confused and overwhelmed by the incorrect speed information.
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During the Aeroperu flight, the crew was able to initiate a landing maneuver. During the landing attempt it stalled and then crashed.
During Air France Flight 447 in 2009, the pitot tube likely froze. However, here the aircraft is already at cruising altitude. When the autopilot then disengaged, the pilots were probably pulled out of the plane by a local stick and tried to bring the jet back under control by pulling the pilot too hard. So they also caused a stall, which led to a crash across the Atlantic.
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