Proficient Pilot: Pulling it around

Raising the landing gear after takeoff, for example, is a procedure, but how soon after liftoff a pilot chooses to raise the gear is a matter of personal preference or technique.

There is one technique that I see with increasing regularity when conducting flight reviews, one that is rapidly becoming one of my pet peeves. This involves pilots—including some flight instructors—who use pitch trim to relieve back-pressure when performing a steep turn. (The FAA apparently does not have an official position about this use of pitch trim.)

The purpose of a steep turn as a training and proficiency maneuver is “to develop and maintain smoothness, coordination, orientation, division of attention, and control techniques,” according to the Airplane Flying Handbook. The maneuver also is used during instrument training to help a pilot develop or demonstrate his ability to scan the flight instruments.

Trimming during the turn does make the maneuver easier to perform, but defeats its purpose as a training exercise. After all, if control wheel forces are trimmed away and the pilot can maintain altitude with his fingertips, the exercise becomes little more challenging than flying straight and level. This is one reason why airline instructors typically do not allow this use of trim.

Another reason for not trimming becomes obvious when having to roll out in hurry. If the pilot cannot retrim quickly enough, or if he forgets to add considerable forward pressure to the wheel, he might find himself involuntarily entering a hammerhead turn.

For similar reasons, pilots should avoid trimming during a landing flare, a practice I have observed a number of times, particularly in aircraft equipped with electric trim. A rejected landing at such a time could result in a powerful, nose-up pitching moment that could produce disastrous results.

The purpose of elevator trim is to relieve control pressure when maintaining a prolonged condition. Trim should not be used for relieving transitory control pressures.

When flight conditions dictate that it is imperative for a pilot to make a steep turn (such as when used as an escape maneuver), it would be of such short duration (180 degrees or less) that there likely would not be enough time or advantage to justify trimming. As a result, using trim during practice is a form of negative training.

Aircraft designers attempt to make it difficult for pilots to inadvertently develop excessive and potentially destructive G loads. They do this by inducing stick forces that became so heavy, it becomes more difficult for a pilot to inadvertently overstress the aircraft.

A given lightplane, for example, might have a designed stick force of, say, 25 pounds per G. This means that a pilot must exert 25 pounds of pull to create one G or 100 pounds to create four Gs. To eliminate or reduce these stick forces by trimming during a steep turn negates the effort of the designer and makes it easier for the pilot to overstress the airplane, especially when attempting to recover from a developing spiral by hauling back mightily on the yoke. The best way to recover from a spiral dive, of course, is to roll out of the turn, raise the nose, and reduce power (if necessary). Under no circumstances should a pilot attempt to salvage a steep turn by just pulling back on the control wheel during a developing spiral. An instructor or an examiner would much prefer to see you swallow your pride, give up the turn, and recover.

Moving an airplane’s center of gravity aft also reduces the pitch force required to create a given number of Gs. If the CG is moved excessively aft, pitch forces become much lighter. In this condition, it is easier than you might imagine, especially in turbulence, to inadvertently create enough of a G load to break something—which is exactly what has happened in a number of accidents.

Conversely, shifting the CG forward increases the stick force required to produce a given number of Gs.

To be fair, an argument in favor of trimming during steep turns is that this can help to prevent a high-speed spiral from developing. That is why such trimming is a matter of technique. Each of us has his or her own preference.

Barry Schiff was designated as an Elder Statesman of Aviation by the National Aeronautic Association in 2004.

Web: www.barryschiff.com