Why aircraft stall

When a plane flies, the air around the wings is at different pressures. At a certain point, the separated flow reaches a critical mass that stops lift generation. Without lift, the aircraft will start to fall no matter how powerful the engines are or how fast it flies. The point where an aircraft wing reaches stalling conditions by raising the nose of the plane is called the critical angle of attack. It is generally over 15 degrees, hence why you rarely see aircraft take off or land at a steep angle.

The basic stall in the modern light aeroplane is very gentle, but it is good aviation practice to secure loose articles to stop them moving around the cabin, and check harness security. Commonly the electric fuel pump is switched on to guard against an airlock refer CFI. In addition, the carburettor heat may be cycled to ensure ice has not formed. Stalling is not carried out over populated areas because large power changes are made throughout the exercise and may disturb people on the ground.

Carry out a minimum of one degree, or two degree, clearing turns, to ensure other traffic will not result in conflict. During the last part of the turn, start looking for a suitable reference point on which to roll out and use for the stall entry.

Common practice is to make these turns in the one direction usually left so that the exercise is carried out in a box over the same ground features. This general practice can be altered to allow for wind direction and strength drift , the training area boundaries, and other traffic. As large power changes will be made, it is appropriate to revise the requirement for smooth but positive throttle movements and the correct use of carburettor heat.

All preflight inspections should include a search for loose articles. Discreetly ensure a sick bag is available. The regular turns and steeper than normal nose attitudes could lead to a level of disorientation — make sure the student has time between stalls to orientate themselves. As the student gains more practice and exposure to stalling, their comfort level will increase, and they should become relaxed about stalling the aeroplane — but never complacent!

The effects of stress are reduced by overlearning the procedure, to produce an initial automatic response, and by experiencing the sensations of the stall, to desensitise the pilot. Tell the student that if they feel uncomfortable at any point, they should say so, the aeroplane can then be flown level, until they feel comfortable to continue.

Because of the high nose attitude at the stall, choose either a high reference point or have the student sight one along the side of the engine cowling. From level flight, carburettor heat is selected HOT and the throttle smoothly closed.

As the nose will want to yaw and pitch down, keep straight with rudder and hold the altitude with increasing backpressure on the control column. The first true symptom is a decreasing airspeed. Low airspeed and a high nose attitude are not always present in the approach to the stall. For example, the high-speed stall as a result of pulling out of a dive too sharply. Therefore, although it is desirable to inform the student that a high nose attitude and low airspeed are indicators of an approaching stall for most phases of flight, they will not always be present.

The next symptom is less effective controls as a result of the lowering airspeed — as they will have experienced in the Slow flight lesson. The student should also recognise the progressively increasing stick forces as the stall is approached. Reduced control effectiveness is usually followed by the stall-warning device. However, this is not a true symptom, as the device is mechanical and may not work. The type and operation of the stall-warning device fitted to the aeroplane should be described.

The last generally noted symptom is the buffet. This is caused by the turbulent airflow from the wings striking the empennage. This is because the airflow breaking off the high wing combined with the high nose attitude, results in most of the turbulent airflow missing the empennage. At this point, as a result of the low airspeed, elevator effectiveness has been reduced to the point where no further increase in angle of attack can be achieved, even though the control column is held well or fully back.

This results in the aeroplane sinking and the change in relative airflow causes the critical angle to be exceeded. The aeroplane stalls, altitude decreases and generally the nose pitches down. It is important the student be able to correctly identify when the aeroplane has stalled. The recovery is broken down into two distinct parts: unstalling the aeroplane, and minimising the altitude loss.

To unstall the aeroplane , the angle of attack must be reduced. Since increasing the backpressure or pulling back increased the angle of attack, decrease the backpressure or check forward. And all aircraft have warning systems to prevent, or alert pilots, to dangers. On a smaller, light aircraft, the most common method involves a simple flap on the leading wing edge, designed to activate a warning if the wing approaches its critical angle of attack. Modern fly-by-wire aircraft will incorporate several systems to alert pilots of an approaching stall.

This includes monitoring of speed and sensors to measure the angle of attack. These sensors are part of the problem that previously grounded the Boeing MAX aircraft. Despite training and warning systems, stalls do still occur.

At low speed and low altitude during take-off and landing, they can be disastrous, and unfortunately, a number of crashes have occurred. Some of the most notable include:. Feel free to discuss aircraft stalling, spinning, or any other aspect of flight performance in the comments. Journalist - With almost a decade of experience in the publishing sphere, Justin has built up a deep understanding of the issues facing aviation today. Read More. Call Us: Skip to content. The Basics of Stalls: What You Should Know A common misconception is that stalls are attributed to a mechanical problem in an airplane.

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