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Stall, a Dreaded Occurrence in Flying?

in Aviation Blog, Flying Tips

As a pilot, the dreaded sound of the Stall Warning Horn in the cockpit is a scary thing if the Stall is not being intentionally induced to practice its recovery. A stall can occur during any phase of a flight regardless of the airspeed; a High-Speed Stall is an even more precarious situation. The angle of attack of an aircraft is more relevant in terms of stalling then the airspeed. However, most of the stalls occur at lower speeds with an increased angle of attack. Normally an angle of attack close to 15 to 16 degrees brings the flow separation above the wings to a level conducive for a Stall in most aircrafts. Different planforms, shapes, aerofoils, camber, thickness, and designs of the wings have their own peculiar Stall characteristics. Power settings, engine types, airspeeds, and configuration of the aircraft have their own roles to play during a Stall.


Just before the onset of a fully developed Stall, the control column begins to shake, and so do the rudders. The buffeting or shaking is due to the disturbed airflow unable to cross the wing aerofoil in a smooth manner; the separated airflow reaches the tail section and the shake starts. The wings are unable to produce sufficient Lift at this stage, and cannot counter the Drag that is already augmented through additional Form Drag produced due to the separated airflow. The result is a Stall, aircraft suddenly loses altitude, and it feels as if you are falling down.

Do I need to be afraid of a stall?

The answer to this question is no absolutely not, and for obvious reasons. Firstly, since a Stall does not happen all of a sudden, it gives ample amounts of warnings before taking place; this allows you to take remedial actions and control the stall in its incipient state. Second reason for not being afraid of a Stall is that even if the stall develops, with prompt correct actions you can recover from it with a little loss of height. This however by no means means that Stall should be taken lightly; it is a potentially dangerous situation and must be avoided at all costs.

A wing drop may occur during Stall, and the aircraft may even go into a Spin if the correct remedial measures are not taken swiftly to arrest the Stall. Loss of height at low altitudes can be very dangerous at times, if one inadvertently enters into a full Stall. Therefore, alertness on part of the pilots is always desirable during critical phases of flight where Stall may take place; the idea is to be able to identify the impeding Stall and take immediate recovery actions to control the situation from aggravating further.

How to Avoid a Stall?

You are most vulnerable to a Stall during conditions of high angle of attacks; some of the additional factors that contribute directly or indirectly are wing loading, planform, wing design, wing shape, and pressure gradient above and below the wings. Every care is being taken by the manufacturers to give sufficient warning of the stall to the cockpit crew; every aircraft is equipped with Stall warning systems that pre-warn the pilots of an approaching stall. The best way to avoid a Stall is by being able to correctly identify the warning signs that alert you to an approaching Stall. A thorough study of the Stall warning systems that are there in the aircraft you fly, must be done in addition to the general and usual universal symptoms of a Stall.

You must practice Stall and its recovery either through a simulator or during actual flying, depending on the type of systems that you fly. Stall should not be allowed to get to the fully developed stage and must be recovered with the very first of the Stall warnings. Reducing the angle of attack and the load factor of the wings, increasing speed if you are at low speeds, and adding power are the immediate actions when you sense an approaching Stall. Taken promptly these simple actions will recover most aircraft from an incipient Stall. Stall is an undesirable possibility during flying; thankfully, every pilot is trained and tested to deal with it and recover out of it.

 

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