Stick and Rudder Fundamental – Recognize and Control P-Factor Yaw

A Chandelle is a 180 degree climbing turn. The defining criteria are (1) constant bank with increasing pitch during first 90 degrees of turn; (2) constant pitch with decreasing bank during second 90 degrees of turn. In this photo the initial bank is set (approximately 30 degrees). The pilot needs only to apply pressure and pull to her maximum pitch. Most pilots never have a chance at a beautiful Chandelle because they fail to control adverse yaw with rudder when establishing bank, and they make a horrible entry into the pitch phase. Imagine a yawing moment applied to the attitude of this photo (a model will help). Rotate the airplane on the “slanted” vertical axis. From the pilot’s perspective, the nose will appear above the horizon; the attitude appears to be pitch – it is not. The airplane is unstable and any pilot control inputs will be misguided.
A Chandelle is a 180 degree climbing turn. The defining criteria are (1) constant bank with increasing pitch during first 90 degrees of turn; (2) constant pitch with decreasing bank during second 90 degrees of turn. In this photo the initial bank is set (approximately 30 degrees). The pilot needs only to apply pressure and pull to her maximum pitch. Most pilots never have a chance at a beautiful Chandelle because they fail to control adverse yaw with rudder when establishing bank, and they make a horrible entry into the pitch phase. Imagine a yawing moment applied to the attitude of this photo (a model will help). Rotate the airplane on the “slanted” vertical axis. From the pilot’s perspective, the nose will appear above the horizon; the attitude appears to be pitch – it is not. The airplane is unstable and any pilot control inputs will be misguided.
This essay is the seventh in a series titled The Top Ten Best Stick and Rudder Habits. In no particular order, I present ten great habits that promote good airmanship.

Caution: If you practice flying maneuvers to improve your flying skills, you should emphasize good technique when using the flight controls. When you practice using the flight controls with poor technique, you become expert at flying bad maneuvers.

Perhaps the most misunderstood and abused flight control during maneuvers is the rudder. The purpose of an airplane’s rudder is to aid in making a cross wind landing and to control yaw in flight. Yaw is an airplane’s rotation on its vertical axis. Yaw is caused by:
1. using ailerons (adverse yaw),
2. propeller P factor during climbing or descending flight,
3. gyroscopic force typically experienced when rotating an airplane on its pitch axis (push or pull on the stick),
4. Pilot over-control.

Last month’s essay spoke to the danger associated with pilot induced yaw (over-control using rudder peddles). This month’s Best Habit is to Recognize and Control P-Factor Yaw.
The best way to learn about P-factor is to face P-factor; one on one, you and the airplane during climbing and descending turns. Please take a moment and consider criteria for a climbing turn (in a puller propeller driven airplane):
1. Start from a constant rate of climb, and trimmed for airspeed at best rate of climb.
2. Establish a turn with a 15 or 20 degree bank. Do not re-trim during the turn. Hand flying is more challenging and the lessons to be learned are more readily apparent.
3. Maintain constant bank angle and airspeed through a continuous turn (360 or 720 degrees). Do not use instruments. Learn to use sight picture.

Start this exercise with a climbing turn to the left. Roll into the turn with aileron and rudder to control adverse yaw (if necessary). Remember to get off the rudder. We are concerned about rate of turn as we maintain constant bank and pitch (airspeed). (You must maintain constant bank and constant pitch).

Key Point: Because P-factor is assisting the turn, you will probably not need rudder input to achieve an acceptable rate of turn.

Watch your sight picture and observe the ball during this climbing turn to the left. Is the ball centered? If not, does rate of turn improve when rudder pressure is applied to “center the ball”? In my airplane, depending upon fuel load and airspeed, the ball will be very slightly right of center; however, the quality of the turn (rate of turn) will deteriorate with application of right rudder pressure to center the ball (step on the ball).

Side Bar: So much for “keeping the ball centered”. Remember use rudder when needed, as much as needed for best results.

Next establish a climbing turn to the right (same criteria). Remember to get off the rudder after controlling adverse yaw. Note the sight picture when established in the turn. (You must maintain bank and airspeed!) In my airplane there is almost no rate of turn. The airplane just “hangs” there with minimal rate of turn. Remember, you must hold constant bank and airspeed during this phase of exercise.

Look at the ball. It will be hard to the right. P-factor yaw is working against the turn. Watch the sight picture as you apply pressure to right rudder (steep on ball). With increasing rudder pressure, the rate of turn increases. Apply and hold rudder pressure as required to keep the ball centered. Take your foot off the rudder and the rate of turn dramatically diminishes. Apply rudder pressure (center the ball) and rate increases dramatically.

Remember to watch sight picture during this exercise. When you apply rudder to “center the ball” you will notice the nose yaw (it drops) and bank increase. You are over-controlling. Because of P-factor yaw, you must force the climbing attitude with excessive elevator and aileron inputs. When you apply rudder as required to counter-act yaw, you will need to release pressures on elevator and aileron to maintain the requisite bank and airspeed.

Key Point: Rudder is required to control P-factor yaw during climbing turns to the right. A pilot’s failure to use rudder correctly is generally compensated for by pilot over-control inputs to elevator and ailerons. Over-control always makes the airplane unstable and is a source of pilot and passenger discomfort.

If you enjoy controlling yaw during climbing turns, then descending turns are a hoot! Set power and trim for descending flight at pattern airspeed for approach to landing (best rate of climb airspeed works). Establish a descending, shallow banked turn to the left. Let go of the flight controls. With your hands off the controls, the airplane should fly a perfectly stable turn to the left, on airspeed with a constant bank. Watch the sight picture; it is a beautiful thing.

Side Bar: Somebody, an aviation pundit, some time ago established left hand traffic as standard. Why not. Hands off, descending left turns are easy, stable and safe. A naturally stable turn is a beautiful thing.

Next, using the same power and trim, establish a descending, shallow banked turn to the right. Let go of the flight controls. Watch the sight picture, and you will see the bank increasing, and the nose falling as the airplane transitions into a steepening spiral. Airspeed is increasing. Descending P-factor yaw is assisting the turn and increasing the roll rate (remember linkage).

Do not let things get out of control; before the airspeed gets too high (less than 10 mph increase), keep your hands off the controls and apply light top rudder pressure (the left rudder peddle). Watch the sight picture to observe initial pitch and bank re-established in response to your nuanced application of top rudder pressure.

Key Point: P-factor causes an airplane to yaw right during descent. Using top rudder against the yaw results in a hands off, perfectly stable, descending turn to the right on airspeed with a constant bank. Watch the sight picture; it is a beautiful thing.

Developing great stick and rudder habits will make you a better pilot, and those great habits will make maneuvers fun. The artistry of a great flyer is apparent when she applies the nuance to Recognize and Control P-Factor Yaw and fly a Fabulous Chandelle.

Click here to see this month’s feature video: The Fabulous Chandelle.

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