Angle of Attack

Private Pilot License (PPL) Notes

This section explains the concept of angle of attack and its critical role in understanding and preventing stalls, emphasizing why a stall can occur at any airspeed or attitude.

Understanding Angle of Attack:

1. A wing can be stalled at any airspeed and any attitude:
   1. This seems counterintuitive but is true due to the role of angle of attack.
2. The critical angle of attack:
   2. The single number that determines if an airplane will stall.
   3. Not displayed on most instrument panels.
   4. Exceeding it causes the wing to stall every time.
3. Angle of attack vs. pitch angle:
   1. They are not the same.
   2. Understanding requires the concept of flight path angle.
4. Flight path angle:
   1. The angle between the flight path vector and the horizon.
   2. Represents the climb or descent angle of the airplane.
5. Calculating angle of attack conceptually:
   1. Subtract flight path angle from pitch angle.
   2. No need for precise calculations in flight.
   3. Use the concept to visualize the approximate angle of attack.

Visualizing Angle of Attack in Flight:

1. Normal climb example:
   1. Pitch angle might be 5 degrees.
   2. Flight path angle is positive due to climbing.
   3. Angle of attack is less than pitch angle.
2. Slow flight example:
   1. Pitch angle is 5 degrees.
   2. Flight path angle is zero (level flight).
   3. Angle of attack is higher than in a climb.
3. Key question to ask:
   1. Where is the airplane pointed compared to where it's moving?
   2. Helps visualize relative wind and angle of attack.

Airspeed as a Proxy for Angle of Attack:

1. Most light airplanes lack angle of attack indicators:
   1. Pilots rely on airspeed to estimate angle of attack.
   2. Pilot's Operating Handbook references stalls in terms of airspeed.
2. Airspeed's reliability:
   1. High airspeed generally means low angle of attack.
   2. Keeping airspeed in the green arc helps prevent stalls.
   3. Stalls typically occur at low airspeeds with nose-up attitudes.
3. Limitations of airspeed as a substitute:
   1. Applies mainly to normal flight conditions (pitch less than 10 degrees, bank less than 30 degrees).
   2. In steep turns or unusual attitudes, airspeed may not accurately indicate angle of attack.

Angle of Attack Indicators:

1. Increasing availability in light airplanes:
   1. Provide real-time angle of attack information.
   2. Useful for pilots of all experience levels.
   3. Help avoid stalls and optimize glides.
2. Usage by professionals:
   • Navy pilots rely on angle of attack for carrier landings.
3. Types of indicators:
   1. Analog indicators with dials ranging from green to red.
   2. Digital indicators displaying colored bars or tapes.
4. Interpreting the indicator:
   1. In cruise flight, angle of attack is low and in the green zone.
   2. During landing, angle of attack increases but should stay out of the red zone.
   3. Some indicators show a "donut" for best glide speed.
5. Using angle of attack indicators effectively:
   1. Treat them as quick-reference tools.
   2. No need to focus on exact numbers.
   3. Ensure indicator stays within safe zones during all phases of flight.

Preventing Stalls Without an Indicator:

1. Maintain awareness of angle of attack:
   1. Consider both pitch attitude and flight path.
   2. Visualize the difference between where the airplane is pointed and where it's moving.
2. Fly smoothly:
   1. Avoid aggressive maneuvers.
   2. Keep airspeed comfortably above stall speed.
   3. Staying within normal flight parameters reduces stall risk.
3. Regular training and practice:
   1. Practice stalls and recovery techniques with an instructor.
   2. Enhances understanding of how angle of attack affects flight.

By understanding and monitoring the angle of attack, you can prevent stalls and ensure safer flight operations, even without specialized instruments.