CFI to CFI
A proper introduction
Why we teach slow flight and stalls
One of the earliest lessons for most student pilots includes an introduction to slow flight and stalls. For people who are new to aviation, the word stall can be misleading and frightening. All too often, when an airplane is involved in an accident, the media reports that it stalled. Because nonpilots are familiar with what happens when our car engine stalls, they assume that a stall in an airplane is the same thing: The engine has quit and will be of no use for the rest of the flight.
When introducing new pilots to the terminology of a stall, it is absolutely critical that instructors use care in how the term is introduced. A stall, in aerodynamic terms, means that the wing has stopped producing lift because it has exceeded the critical angle of attack. In layman terms, that means that as we slow an aircraft down, we must raise the nose, and thus the angle of attack, to sustain the necessary lift to maintain altitude at the desired airspeed. If that angle of attack gets too high, the wing can no longer produce lift because the smooth flow of air over the wing is disrupted. The wing stops flying, and the nose drops. The only way to resume normal flight is to reduce the angle of attack and reestablish proper lift.
Slow flight, then, is a precursor to stall training. Slow flight serves two purposes. The first is to familiarize the student with the flight characteristics of the airplane at the low end of the speed regime. Because landings are a form of slow flight, it makes sense to be comfortable with flying slow. The controls are mushy, the sound is different, and the panel obscures the view out the window. The second purpose of slow flight is to learn how to recognize when the aircraft is close to the onset of a stall. At the minimum controllable airspeed, the stall horn or light may be making noise or illuminating, and the airplane may occasionally burble. The point of this exercise is to demonstrate how to recognize an imminent stall.
While the ability to recover from stalls is indeed important, the hope is that by teaching a student how to recover from the stall itself, he or she will learn to recognize the flight characteristics associated with an imminent stall and recover before the stall occurs. At low altitudes, this is critical, and part of the training will be to execute a stall recovery with an absolute minimal loss of altitude. The same can be said of the takeoff/departure stall, in which the student will apply full throttle and pitch up until the stall occurs. In reality, these stalls occur when a pilot is trying to clear an obstacle at the end of the runway after takeoff.
One of the most important aspects of stall and slow flight training is to learn when such events are most likely to occur. An approach to landing stall will occur prior to landing. In theory, it could occur any time after you reduce power for your approach in the traffic pattern. A student might find himself in a deteriorating situation that is outside his normal reference. For example, he might be landing at an airport with a control tower, and the tower might ask him to extend his downwind. If he has minimal experience in a busy environment, he might find himself descending lower than he should, and when he turns base or final, he might be low and slow -- a potentially disastrous combination -- and if it's a solo flight you won't be there in the right seat. Slow flight and stall training will teach students to recognize the potential danger and how to recover as safely and quickly as possible.
Slow flight and stalls can invoke a lot of fear in student pilots, especially if they have heard any "there I was..." horror stories about the dangers of stalls. Sometimes, students read more into their textbooks than really is there and get a little spooked as well. One of the most effective methods of dealing with this fear is to meet it in a gradual sort of way. A good CFI will take the time to explain how slow flight will be entered, what the response of the airplane will be, and how to anticipate what will happen next. A tentative student might want to start by slowing down only 10 or 15 knots, then recovering to normal speed. Once comfortable with that, have them enter slow flight again, and slow an additional 10 to 15 knots, with additional flaps as necessary. Recover to normal cruise, then re-enter slow flight, reducing speed further. Eventually you will be flying at minimum controllable airspeed.
Once the student is comfortable with slow flight, spend some time on the ground reviewing the definition of a stall and the entry and exit procedures. I've always been a firm believer in introducing stalls incrementally, doing them initially with the first notch or setting of flaps, and then recovering. Add each flap setting incrementally. This will demonstrate the changes in the flight characteristics as the shape of the airfoil changes. It will also reduce the shock effect of doing a stall with full flaps right off the bat. Another item to keep in mind: If the day comes when a student finds himself in an airplane with flaps that don't work, shouldn't he be familiar with the way the airplane handles? Stall speed increases as flaps are reduced, so it pays to learn the changes during training, instead of having to find out the hard way.
To just jump in an airplane and introduce a student to full stalls without proper ground training is both unfair and irresponsible.
With regard to takeoff stalls, if the airplane has a short-field or soft-field takeoff procedure that utilizes flaps, it is wise to do a few power-on stalls with those flap configurations, again to gain a vision of what such a situation may present.
Slow flight and stalls are important skills. They not only prepare your students for the task of learning to land, they teach just how versatile the aircraft is, and how to handle an inadvertent foray into the lower end of the performance arena. Just as a golfer must practice getting out of a sand trap, students must practice getting out of both an imminent and an actual stall. And like the golfer, it is important to keep the skills sharp with regular practice.
Chip Wright has been flying since 1990, has been a CFI since 1994, and is now an ATP and a Canadair Regional Jet captain for Comair. His total time is 8,000 hours.
By Charles Wright