Setting Up for the Stall
The airplane is climbed to a safe altitude, and a clearing turn is performed. A clearing turn is a maneuver in which the airplane is turned, while the pilot thoroughly scans for any air traffic in the area, prior to commencing the stall maneuver.
The airplane is then slowed, and flaps and gear are extended. The pilot sets the engine power to the landing approach power setting, and enters a descent as the approach speed. This simulates the airplane being on approach for landing.
Performance of the Stall
The power is reduced to idle, and the airplane is leveled. The pilot continues to add back pressure to the flight controls, maintaining altitude and allowing the airplane to become too slow.
As the airplane slows, recognizable warning signs of an impending stall appear. The controls are mushy and ineffective. Excessive back pressure is applied to the control yoke. The airplane is in a nose up orientation, a climbing orientation. Yet, the airplane is not climbing. The airplane is very quiet, due to the absence of wind noise.
At this point, the airplane's stall warning system activates. In some airplanes a stall warning light will illuminate. In others, a loud audible stall warning horn will sound.
A vibration can be felt in the airframe. This vibration is the stall buffet, which results from the turbulent airflow over the wings.
The pilot continues to hold full back pressure. The airspeed indicator shows a very low airspeed, and may even drop to indicate zero airspeed. The wings become fully stalled, and the airplane begins to descend on it's own. Most of the time, the airplane will "break", the nose falling sharply downward at the moment of the stall. Once the airplane is fully stalled, the pilot initiates a stall recovery.
Recovery
The pilot recovers from the stall by reducing back elevator pressure and adding full power. The stall warning system ceases. The rush of air is an audible indication the airplane's speed is increasing. The pilot observes the proper airspeed indication. The airplane is no longer in a stall, but is now descending undesirably.
The pilot arrests the descent by placing the airplane in the nose up, climb orientation. This orientation is very similar to the airplane's orientation just prior to the stall. However, the feel and performance is very different now that the airplane is not stalled.
The airplane levels off and begins to climb, as the pilot retracts the flaps and gear, according to the recovery procedures specified by the airplane's manufacturer.
Recovery from and Impending Stall
In addition to recovery from a fully stalled condition, you will also learn to recovery the airplane just prior to the stall. The setup and recovery are the same. However, this time, the student points out that a stall is imminent and initiates recovery immediately.
Turning Stalls
Your flight instructor will also teach you to perform stalls while turning. This is meant to simulate a situation in which the pilot begins to get too slow while on maneuvering for a landing. Setup and recovery for a turning stall is the same. The pilot just levels the wings and maintains whatever heading the airplane was on when the stall recovery was initiated.
Use of Ailerons and Rudder
When the airplane is stalled, the ailerons are not very usable. The ailerons work by increasing angle of attack over a portion of one wing, while lowering it over a portion of the other wing.
If the airplane is stalled, however, the ailerons might do very little. It's possible they might even induce a roll in the opposite direction. For example, if the pilot desired to roll right during a stall, the pilot would turn the control wheel to the right, raising the right aileron and lowering the left. The raised right aileron decreases the angle of attack over its portion of the right wing. At the same time, the lowered left aileron increases the angle attack over its portion of the left wing.
Under normal circumstance, this results in the right wing producing less lift, while the left wing produces more, rolling the airplane right. However, if both wings are stalled, raising the right aileron decreases the angle of attack. This lessens the stall, allowing the right wing to produce more lift. Meanwhile, the lowered left aileron deepens the stall over the left wing, causing it to produce less lift.
So the pilot could put in full right aileron during a stall, and the airplane could react by rolling left.
The solution to this problem is for the pilot to use rudder to control the aircraft during the stall. Ailerons are usable before and after, but not during.
A common airplane design involves building the wings with a small twist. This twist makes the outer portions of the wings less stalled than the wing root, located near the cabin. As a result of this design feature, the ailerons should roll the airplane the correct way throughout the stall maneuver. This design is meant to aid the pilot who instinctively respond by adding right aileron and right rudder during a stall. Proper recovery technique calls for the ailerons to remain in the neutral position during the stall.