January 1, 2009
By Barry Schiff
Retired TWA captain Barry Schiff has been a flight instructor since 1956.
Last month I administered a flight review to a 165-hour private pilot in a Cessna 172P. He did an excellent job except for displaying one habit that drove me nuts. He never used the rudder pedals in the air. As a result, his turn entries and recoveries were sloppy, and he held the airplane in a slight right bank during climb to maintain a constant heading in compensation for P-factor, the left yawing tendency of a single-engine airplane being flown under power at large angles of attack.
I called his attention to the errant behavior of the slip-skid ball several times during the flight, but he never seemed to understand what I meant by this.
After discussing this problem with him on the ground, I realized that he had never been taught the proper use of rudder. How, I wondered, could he have gotten this far without someone noticing and applying some instructive correction? This led me to have a talk with his original instructor. The instructor explained to me that the Cessna 172 has so little adverse yaw effect and so little left-turning tendency during climb that he found it easier to simply ignore these facts of flight and teach his students to fly the airplane with their feet flat on the floor (figuratively speaking). I kid you not.
Then he tried to rationalize this attitude by reminding me that a two-axis autopilot maintains heading in a climb by lowering the right wing slightly to offset P-factor. I wanted to ask him why he would not apply some right rudder to assist the autopilot and keep the wings level, but I did not think that this would impress him. I drove home feeling as though I had just come through the twilight zone. Surely, I thought, such an attitude was an aberration. But I did find myself wondering if this tolerance for sloppy flying was more pervasive. After all, this instructor’s students were managing to satisfy examiners and passing their flight tests.
Some years ago I said that if I was the king of the FAA I would require all aspiring pilots to take their first lessons in a glider. This is because gliders (or sailplanes) are intolerant of improper rudder usage. They have such long wings and the ailerons are so far from a glider’s longitudinal axis that adverse yaw effect is amplified. Entering or recovering from a turn without applying substantial rudder results in noticeable and uncomfortable slipping (unless the seat of one’s pants is insensitive to such sideways movement).
Furthermore, gliders (or sailplanes) used as trainers are equipped with a few inches of yarn taped at one end to the center of the windshield. Anything less than perfect coordination of aileron and rudder causes the yarn to deflect one way or the other (away from the slip). The length of yarn visually chastises pilots for accepting any sloppiness. The goal is to maneuver in such a way as to keep the yarn flowing straight back and without leaning left or right, a difficult challenge to master until developing the proficiency needed to anticipate and prevent slips and skids.
Some instructors claim to use similar strands of yarn taped to the windshields of airplanes to teach students about aileron-rudder coordination. It apparently works well in some airplanes but not in all. It depends on how propwash affects airflow about the windshield. (It works best on airplanes with pusher engines.) It is worth trying on any airplane, however, because there is so little to lose and so much to gain.
I have always believed that those who learned to fly in old taildraggers such as the Aeronca Champion and the Piper J-3 Cub were better stick-and-rudder pilots because these aircraft were so much more demanding.
Adverse yaw effect is so pronounced in these aircraft that one can even observe it while taxiing into a strong wind. I used to demonstrate this to students by heading directly into the wind and moving the stick abruptly left. The airplane would respond by beginning a taxiing turn to the right because of the drag created by the lowered aileron (which is greater than the drag of the raised aileron on the other side). I would then ask my students to make S-turns along the taxiway using only the control stick. It provided a dramatic demonstration of adverse yaw effect.
One could argue that there is nothing dangerous about a little slipping and skidding, to which I would respond, “You wanna’ bet?”
Imagine a pilot flying a single-engine airplane in a full-power climb and holding right aileron to maintain heading. Now assume that he allows the nose to get too high. Airspeed wanes and the airplane approaches a stall. Additional right aileron is added to compensate for the strengthening adverse yaw effect. When the airplane finally does stall, the pilot winds up applying full right aileron to prevent the airplane from yawing left. Bingo! He has inadvertently entered a left spin. Continuing to hold right aileron in a futile attempt to raise the lowered wing simply aggravates and intensifies the spin.
Spin recovery requires idling the engine, neutralizing the ailerons, applying full anti-spin rudder, and applying nose-down elevator (four steps easily remembered using the acronym, PARE). The problem is that a pilot lacking habitually proper stick-and-rudder skills may not have the ability to recover from the spin in a timely fashion, if at all.
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