Slow Flight and Stalls
Slow Flight Overview
Slow Flight Definition:
Slow flight refers to flying at a speed between stall speed and maximum endurance speed. Specifically, it is typically 5 to 10 knots above stall speed.
Purpose of Learning Slow Flight: To recognize symptoms before stalling an aircraft.
Power Curve and Slow Flight Fundamentals
Power Curve:
The total power required to maintain level flight changes with airspeed.
Slower flight speeds require disproportionately higher power to maintain altitude due to increased drag.
Drag Types:
Induced Drag:
Drag caused by the air pressure differentials created by the wings. It increases significantly as the angle of attack increases.
Parasitic Drag:
Drag created by non-lifting parts of the aircraft, such as the wheels and struts. This drag decreases as airspeed decreases initially but eventually increases due to air resistance at lower speeds.
Recognizing Slow Flight
Four Main Indicators of Slow Flight (Important for Flight Tests):
High RPM but Low Airspeed:
The engine can run at high revolutions while the aircraft moves slowly.
Stall Horn Activation:
The stall warning horn may activate, warning the pilot of an impending stall.
Ineffective Flight Controls:
At slow speeds, ailerons and other flight controls are not very effective.
Asymmetrical Thrust:
High angle of attack of the propeller creates asymmetric thrust, requiring a right rudder to counteract roll tendencies.
Power, Attitude, and Performance
Equations of Flight Performance:
Attitude + Power = Performance:
Changing one aspect (attitude or power) requires adjustments in the other to maintain optimal performance.
Effective Control with Flaps:
Deploying flaps increases lift and drag, facilitating slower flight at similar altitudes and potentially improving visibility by lowering the nose of the aircraft.
Safety Considerations During Slow Flight
Engine Cooling:
Aircraft engines are cooled by airflow; during slow flight, the nose-high attitude decreases airflow, making it necessary to periodically lower the nose to allow better ventilation.
Visibility Considerations:
Slow flight can result in significantly reduced visibility, necessitating constant lookout by the pilot.
Practice Environment:
Avoid practicing slow flight in turbulent conditions as it can hinder proper learning.
HAZEL Check for Safety during Slow Flight
HAZEL Check Components:
Height:
Must maintain a minimum of 2,000 feet AGL (Above Ground Level).
Area:
Avoid populated or built-up areas and remain over open land.
Security:
Ensure all items (backpacks, binders) are secured to prevent injury during maneuvers. Verify that seatbelts are fastened and doors and windows are secured.
Engine Health:
Perform checks on the engine's condition, ensuring good performance.
Lookout:
Continuous visual checks for traffic are crucial during turns and maneuvers.
Procedures for Slow Flight and Stalls
Initial Setup for Slow Flight:
Start with Engine RPM:
Usually around 2,100 RPM to set up for endurance flight.
Pitch Control:
Gradually pitch up to decrease speed while maintaining altitude.
Power Management:
Use engine power to control altitude effectively.
Recognition of Slow Flight:
Monitor for the presence of high RPM and the stall horn, and be aware of decreasing control efficacy.
Exit from Slow Flight Maneuver:
Apply full power, pitch forward to maintain altitude, and transition to cruise speed and altitude.
Conclusion and Next Steps
After discussing and practicing slow flight, a brief overview of stalls will follow before flying, with an anticipated flight duration of approximately 30 minutes.