Autorotation with Turns in a Single-Engine Helicopter

Objective

Upon completion of this lesson, the student will demonstrate proficiency in performing autorotation with turns in a single-engine helicopter per FAA-S-ACS-15 PH.VI.C. The student will execute autorotational descents with proper turn entries, maintain coordinated flight throughout the maneuver, demonstrate energy management principles, and complete turns within specified altitude parameters while maintaining positive aircraft control.

Content

Regulatory Requirements

Per 14 CFR 61.87(o), student pilots must receive training in autorotational approaches. 14 CFR 61.107(b)(3) requires private pilot applicants to demonstrate proficiency in performance maneuvers including autorotations. This training directly supports the requirement for private pilots to demonstrate competency in emergency procedures per 14 CFR 61.107(a)(7).

Aerodynamic Principles of Autorotation with Turns

Autorotation is the helicopter’s natural safety feature where the rotor system continues to turn and produce lift through upward airflow caused by the aircraft’s descent. When we add turns to autorotation, we’re combining two complex aerodynamic states that require precise energy management.

Think of autorotation like a maple seed falling from a tree - it spins as it falls, using the upward airflow to slow its descent. In a helicopter autorotation, the rotor disc becomes that maple seed, but much larger and more controllable.

During autorotational descent, the rotor disc is divided into three regions:

• Driven region (root area): Airflow moves the blade backward, creating drag
• Driving region (mid-span): Airflow drives the blade forward, maintaining rotor RPM
• Stall region (tip area): High angle of attack causes blade stall

When we add turns, we must manage the additional complexity of asymmetric lift. In a right turn during autorotation, the advancing blade (left side in American helicopters) experiences higher relative airflow, while the retreating blade (right side) sees reduced airflow. This creates a rolling moment that must be controlled with cyclic inputs.

The key principle: Energy equals life in autorotation. We have only the energy stored in rotor RPM and altitude. Every control input - especially turns - costs energy that we cannot recover without power.

Entry Procedures and Altitude Management

Entry altitude is critical for safety. The ACS mandates minimum 700 feet AGL, but higher altitudes provide better energy management options. In strong wind conditions, additional altitude compensates for increased sink rates and allows more time to establish the autorotation before beginning turns.

Entry sequence:

1. Establish autorotational descent at appropriate airspeed (typically 65-75 knots depending on helicopter type)
2. Stabilize descent rate and rotor RPM within normal limits
3. Verify adequate altitude for turn completion above 300 feet AGL

Turn Execution and Energy Management

The ACS requires either two 90-degree turns in the same direction or one continuous 180-degree turn. The 180-degree requirement refers to ground track change, not heading change - this accounts for wind drift effects.

Turn techniques:

• Shallow bank angles (15-20 degrees maximum) to minimize energy loss
• Coordinated flight using anti-torque pedals to prevent skidding or slipping
• Smooth control inputs to avoid rapid energy dissipation
• Constant monitoring of rotor RPM, airspeed, and altitude

Energy management during turns follows the principle of conservation - what we lose in forward airspeed converts to increased descent rate. The goal is managing this exchange efficiently while maintaining positive control.

Risk Management Considerations

Altitude Management: The 300-foot AGL limitation provides the safety margin for power recovery. Below this altitude, insufficient time and energy remain for safe power application and go-around execution. This altitude accounts for typical helicopter power recovery time and the need to arrest descent rate before ground contact.

Energy State Awareness: In autorotation with turns, we’re constantly trading energy. Unlike powered flight, there’s no energy source to replace what we lose. Each turn costs airspeed and rotor RPM that converts to altitude loss. Poor energy management leads to insufficient flare energy for landing.

Turn Direction Consistency: Multiple turns in the same direction maintain predictable energy patterns and avoid the confusion that can result from direction changes during a critical flight phase.

Weather Considerations: Strong winds increase descent rates and affect turn execution. Turbulence can cause rapid energy loss through control corrections. Plan for higher entry altitudes in challenging conditions.

Power Recovery Procedures: Every autorotation with turns must include planning for power recovery. Know the power recovery sequence: lower collective smoothly, add power progressively, level wings, establish normal flight attitude.

Schedule

Equipment

• Helicopter suitable for autorotation training (per POH limitations)
• Current sectional chart for training area
• FAA-H-8083-21B Helicopter Flying Handbook
• Helicopter Pilot’s Operating Handbook (POH)
• FAA-S-ACS-15 Private Pilot Helicopter Airman Certification Standards
• Kneeboard with autorotation checklist
• Stopwatch for timing exercises
• Training area chart with altitude references and emergency landing sites

Instructor Actions

1. Brief the aerodynamic principles of autorotation, emphasizing the three rotor disc regions and how turns affect energy management
2. Demonstrate entry procedures from 1,000 feet AGL, establishing proper airspeed and descent rate before initiating turns
3. Show turn execution technique using shallow bank angles and coordinated control inputs while maintaining energy awareness
4. Explain energy management by demonstrating how bank angle affects descent rate and rotor RPM decay
5. Practice altitude awareness by calling out altitude throughout the maneuver and demonstrating the 300-foot recovery decision point
6. Demonstrate power recovery procedure from various points in the turn sequence
7. Guide student practice with verbal coaching on energy state, control coordination, and altitude management
8. Provide immediate feedback on control technique, energy management decisions, and safety practices
9. Simulate decision scenarios where power recovery becomes necessary due to altitude or energy constraints
10. Debrief each attempt focusing on energy management effectiveness and safety decision-making

Student Actions

1. Execute proper autorotation entry from instructor-specified altitude, establishing stabilized descent before turn initiation
2. Maintain coordinated flight throughout turn sequences using appropriate anti-torque pedal inputs
3. Monitor energy state continuously by observing rotor RPM, airspeed, and altitude trends during turns
4. Execute turns per ACS requirements - either two 90-degree turns in the same direction or one 180-degree turn based on ground track
5. Maintain shallow bank angles to minimize energy loss while achieving required turn performance
6. Call out altitude continuously during descent, especially approaching the 300-foot AGL decision point
7. Demonstrate power recovery when directed by instructor or when reaching minimum safe altitude
8. Verbalize energy management decisions explaining control inputs and their effects on aircraft energy state
9. Practice emergency decision-making by determining when continued autorotation is safe versus when power recovery is required
10. Self-assess performance after each attempt, identifying energy management successes and areas for improvement

Completion Standards

Per FAA-S-ACS-15 PH.VI.C, the student demonstrates satisfactory performance when they:

1. Enter autorotation at minimum 700 feet AGL or higher altitude as appropriate for wind conditions, establishing stabilized descent before turn initiation
2. Complete required turns consisting of either two 90-degree turns in the same direction OR one continuous 180-degree turn measured by ground track change
3. Maintain coordinated flight throughout all turns with no skidding or slipping as evidenced by centered ball indication
4. Roll out of turns by 300 feet AGL or initiate power recovery and go-around as directed by evaluator
5. Maintain positive aircraft control with smooth control inputs and appropriate energy management throughout the maneuver
6. Demonstrate energy awareness by maintaining rotor RPM within manufacturer’s specified autorotation range
7. Execute proper power recovery when required, smoothly applying power and arresting descent rate
8. Verbalize risk management by calling out altitude and energy state throughout the maneuver
9. Complete maneuver safely without exceeding aircraft limitations or compromising flight safety at any point

The task is considered unsatisfactory if the student fails to roll out of turns by 300 feet AGL and does not perform power recovery when directed, or if any other ACS standard is not met during the performance.