Safety Corner

Stall/Spin

October 1, 1978

Reducing the sting

While the Federal Aviation Administration and the National Transportation Safety Board search out ways to eliminate a recurring aviation killer, indications are that pilot education remains the best way to reduce the frequency of stall/spin accidents. Just how such information is transferred to the pilot is apparently a point of contention.

There were 723 stall/spin accidents from 1974 to 1976 that left 688 persons dead and an additional 246 seriously injured, according to the most recent NTSB report on the subject. The thrust of the board's recommendation was aimed at calling more attention to stall training at the instructional level. It also suggested that "intentional spin training has a positive influence toward reducing inadvertent stalls and spins."

"Innovative and coordinated efforts by the aviation community to significantly reduce general aviation accidents involving aircraft stalls and spins" were urged by the NTSB back in 1972. It called upon the FAA to "organize, direct and integrate stall/spin accident prevention" after a statistical study from 1967 to 1969 recorded 1,261 stall/spin accidents, causing 997 fatalities and 464 serious injuries. "... additional training and education is needed .... "The report also asked the FAA to consider "at least minimal spin training of all pilot applicants."

Interestingly enough, the NTSB's latest recommendations are based on information from an FAA-contracted report — "General Aviation Pilot Stall Awareness Training Study" — which grew out of the NTSB's earlier revelation. However, the board claimed that it was aware of no effort or plans on the part of the FAA to implement the information gleaned from that study. In view of that, the board elected to urge the FAA to consider utilizing elements of its own study in an effort to make flying safer.

It seems incongruous that so many stall/spin accidents occur, because familiarity with stalls and stall recovery is a rudimentary part of learning to fly. The statistics, however, appear to indicate that a significant part of the aviation population lacks a complete awareness of the factors affecting stalls.

A stall occurs when one or both wings lose substantial lift because the pilot has flown the airplane at an excessive angle of attack in relation to the relative wind. A given aircraft will always stall at the same angle of attack. Unlike the stall speed of an airplane, the angle of attack is unaffected by the aircraft's weight, power setting, altitude or load factor. A spin can be a by-product of a stall, often encouraged by an uncoordinated stall recovery.

A stall/spin configuration can be especially deadly when flaps and gear are down and the aircraft is low and slow. That is borne out by the severity of accidents that occur during the approach and departure phases of flight; the pilot might be easily distracted in the airport environment and sufficient altitude may not be available to recover from a stall. Unwarranted low altitude flying and engine-out emergencies account for their share of stall/spin accidents as well.

The record would seem to indicate that often a pilot apparently fails to recognize the onset of a stall and take corrective action to prevent it. That is especially disturbing. Proficiency in handling an aircraft must include a "hands-on" knowledge of its stall characteristics and appropriate recovery actions. Although recovery technique is basic — reduction of the angle of attack — specific traits of an airplane will vary from model to model as the stall regime is approached, entered and recovered.

Those characteristics may be either very docile or demanding, and some aircraft may exhibit more of a tendency to enter a spin than others. In any event, those mannerisms can be surprising to the student or veteran flier when they are encountered unexpectedly, considering the wide range of experience levels represented in the stall/spin accident records.

Exploration of the stall regime should include operation over a wide range of attitudes, power settings and aircraft configurations. beyond the basics required for a flight check, as well as low-speed maneuvering. This allows the flier additional intimacy with an aircraft's behavior and the opportunity to obtain a clear picture of its stall parameters, especially in recognizing the onset of an impending stall.

Stalls are sometimes approached with trepidation, in part, perhaps, because of their proximity to spin entry. That anxiety may very well create a hesitancy to practice stalls and to maintain proficiency, making the pilot more vulnerable to encountering one unexpectedly. Any pilot who finds himself in an unintentional spin for the first time has a right to be anxious, even though the recovery procedure is relatively straightforward. It generally calls for a power reduction, neutral ailerons, opposite rudder from the direction of rotation, neutral rudder when rotation stops, and forward elevator, followed by recovery from the dive. Some aircraft will recover from a spin if the pilot releases all the controls.

Reading a recovery procedure and implementing it for the first time in an emergency are two different animals. And the pilot should be aware that some airplanes are not designed to spin, especially twins, and recovery from some spin configurations may be impossible.

Spin training requirements for pilots is the subject of considerable debate. The AOPA Air Safety Foundation supports spin training, according to William Stanberry, executive vice president. He believes that a thorough knowledge of the stall regime should include spin recovery. Doing it allows an aviator to build confidence, know more about his airplane and 'learn-by-doing' how to recover from a spin.

Stanberry said the foundation is also encouraging the development of an inexpensive angle-of-attack indicator, a far more reliable stall warning device than the various lights, horns and whistles presently employed on most general aviation aircraft.

While government agencies wrestle with a solution to reduce the stall/spin accident tally, pilots continue to add themselves to the list. In the final analysis, the pilot will have to honestly evaluate his skills and recognize whether or not he is proficient in handling his aircraft, including stall recognition and recovery. Although spin training is not required, the aviator may elect to be exposed to that element of flight with a qualified instructor in order to effectively cope with the unexpected.