AFH 5-12

Common Errors Common errors in the performance of slow flight are: 1. Failure to adequately clear the area 2. Inadequate back-elevator pressure as power is reduced, resulting in altitude loss 3. Excessive back-elevator pressure as power is reduced, resulting in a climb followed by rapid reduction in airspeed 4. Insufficient right rudder to compensate for left yaw 5. Fixation on the flight instruments 6. Failure to anticipate changes in AOA as flaps are extended or retracted 7. Inadequate power management 8. Inability to adequately divide attention between airplane control and orientation 9. Failure to properly trim the airplane 10. Failure to respond to a stall warning Stalls A stall is an aerodynamic condition which occurs when smooth airflow over the airplane’s wings is disrupted, resulting in loss of lift. Specifically, a stall occurs when the AOA—the angle between the chord line of the wing and the relative wind—exceeds the wing’s critical AOA. It is possible to exceed the critical AOA at any airspeed, at any attitude, and at any power setting. [Figure 5-8] Figure 5-8. Critical angle of attack and stall. For these reasons, it is important to understand factors and situations that can lead to a stall, and develop proficiency in stall recognition and recovery. Performing intentional stalls will familiarize the pilot with the conditions that result in a stall, assist in recognition of an impending stall, and develop the proper corrective response if a stall occurs. Stalls are practiced to two different levels: ⦁ Impending Stall—an impending stall occurs when the AOA causes a stall warning, but has not yet reached the critical AOA. Indications of an impending stall can include buffeting, stick shaker, or aural warning. ⦁ Full Stall—a full stall occurs when the critical AOA is exceeded. Indications of a full stall are typically that an uncommanded nose down pitch cannot be readily arrested, and may be accompanied by an uncommanded rolling motion. For airplanes equipped with stick pushers, their activation is also an indicator of a full stall. Although it depends on the degree to which a stall has progressed, some loss of altitude is expected during recovery. The longer it takes for the pilot to recognize an impending stall, the more likely it is that a full stall will result. Intentional stalls should therefore be performed at an altitude that provides adequate height above the ground for recovery and return to normal level flight.