Stalls For Instructors
Special CFI RequirementsAre you familiar with the stalls required by the practical test standards (PTS) for flight instructors? Would-be CFIs must be able to perform five types of stalls, including power-on and power-off stalls and three demonstration stalls. The demonstration stalls are found only in the PTS for flight instructors. However, in the interest of safety, pilots in general would be wise to learn about these maneuvers.
The flight instructor applicant must exhibit instructional knowledge by explaining the hazards of these demonstration stalls, how they occur, and how recovery is achieved. But first, a word about power-on and power-off stalls.
Power-on stalls are sometimes not fully understood, particularly in the case of high-performance aircraft. Some instructors have the impression that full throttle is required, but it is not. Using climb power, especially in multiengine and high-performance airplanes, can result in excessively high pitch attitudes and make recovery difficult.
In high-performance airplanes, the power setting for power-on stalls may be reduced to no less than 55 to 60 percent of full power so that the stall can be achieved with pitch no higher than 20 degrees. The objective of the maneuver is to identify the stall rather than to stand the airplane on its tail. Private pilot candidates announce the buffeting or de- cay of control effectiveness and recover promptly after the stall occurs by decreasing pitch attitude and applying appropriate power for returning to level flight with a minimum loss of altitude.
Commercial pilot candidates also set power at no less than 55 to 60 percent of full power on high-performance airplanes and maintain a specified heading within 10 degrees or a bank angle not to exceed 20 degrees in turning flight. The pilot announces the onset of buffeting or decay of control effectiveness, then recovers promptly as the stall occurs by reducing pitch and adjusting power to cruise with a minimum loss of altitude.
For power-off stalls, the private pilot applicant establishes a stabilized glide in the landing configuration with a gear and flap setting as specified by the examiner. The applicant lifts the nose and announces indications of buffeting or decay of control effectiveness and recovers promptly after the stall occurs with minimum altitude loss. The commercial pilot applicant announces the onset of the stall and recovers promptly as the stall occurs. Note the difference for recovery. The private pilot applicant recovers after the stall occurs, and the commercial pilot applicant recovers as the stall occurs.
The three demonstration stalls listed in the instructor PTS are crossed-control stalls, elevator trim stalls, and secondary stalls. Demonstration stalls are not required to a level of proficiency. The reason there is no set proficiency level is the unexpected nature of what might happen, depending on the characteristics of the airplane being used. Instructors are expected to teach pilots the hazards of these stalls and measures to prevent them from occurring in the first place.
On the CFI flight test, the applicant will perform at least one demonstration stall. The applicant will explain how a student would be taught the hazards of these stalls and how to avoid them. (See Aviation Flying Handbook, FAA-H-8083-3, Chapter 5.) Instructors should teach demonstration stalls to all students, but students should not practice them, especially not when flying solo.
The crossed-control stall involves moving the ailerons in one direction and rudder in the other. The pilot, turning from base leg to final approach with slow airspeed and controls crossed, risks a stall or spin. This stall is particularly dangerous because of the potential for spin at low altitude. The hazard is overcome by holding appropriate airspeed with good coordination. Avoid cross-controlling. This is appropriately demonstrated at an altitude of 3,000 feet agl or higher.
The elevator-trim stall may be demonstrated by the instructor at altitude by placing the airplane in a gliding approach similar to final approach for landing. The instructor trims for landing to achieve a hands-off glide and then applies go-around power, allowing the nose to rise until the critical angle of attack is reached. The nose will be dangerously high. The speed will slow quickly as the airplane reaches a pitch attitude that is obviously too high. As the stall angle of attack is reached, the instructor will recover to level flight by reducing the angle of attack and adjusting power for level flight with minimum loss of altitude. This simulates what can happen on a go-around procedure.
The instructor now turns the controls over to the pilot, and the student is told to advance to full throttle. The nose of the airplane will start to rise. However, instruct the pilot to hold forward pressure on the stick or yoke to prevent the nose from rising above a normal climb. Forward pressure will be extreme. You want the pilot to experience how much forward pressure is required to prevent excessive pitch.
The objective is to avoid an excessively high pitch by pressing the control forward. The instructor now instructs the pilot to recover by lowering the nose to level flight, raising the flaps, and adjusting the trim for normal flight with minimum loss of altitude. The purpose of this exercise is to illustrate the hazards of go-arounds and demonstrate the appropriate preventive measure.
The third demonstration stall, the secondary stall, may occur after recovering too abruptly from a previous primary stall. This can happen during initial climb after takeoff or during a go-around procedure. It may be demonstrated with quick back pressure just after a stall occurs. You can demonstrate this during a glide or steep turn. A secondary stall may also occur during spin recovery.
Accelerated Maneuver Stall
Although not required by the CFI test and not one of the demonstration stalls, the accelerated maneuver stall is worth mentioning. All stalls are the result of an excessively high angle of attack, regardless of speed. Accelerated stalls may occur at any indicated airspeed when excessive back elevator pressure is applied. To recover, simply reduce back pressure.
As an instructor, it's important to teach your pilots the hazards of all of these stalls. Explain situations in which the stalls may occur and emphasize how to avoid the hazards and recover with minimum loss of altitude. Teach demonstration stalls to all of your students, too. An effective way to promote safety is to teach these stalls during flight reviews.
By Ken Medley