Autorotation with Turns in a Single-Engine Helicopter

Objective

By completion of this lesson, the student will demonstrate the ability to safely perform autorotation with turns in a single-engine helicopter in accordance with FAA-S-ACS-15 PH.VI.C. The student will establish and maintain autorotational flight with proper energy management, execute coordinated turns to reach a designated landing area, maintain rotor RPM within normal limits, roll out no lower than 300 feet AGL, and execute power recovery to a stabilized hover within 200 feet of the designated point while demonstrating comprehensive understanding of autorotational aerodynamics and risk factors.

Content

Regulatory Foundation

14 CFR 61.87(n) requires demonstration of autorotation procedures before solo flight. 14 CFR 61.107(b)(3) mandates autorotation training for private pilot certification. 14 CFR 91.119 establishes minimum safe altitudes that affect autorotation training areas.

Autorotation Aerodynamics and Energy Management (PH.VI.C.K3)

Autorotation is powered flight without engine power. When the engine fails or is deliberately disengaged, the helicopter becomes a glider with the main rotor as the wing. Upward airflow through the rotor disc drives the rotor system through aerodynamic forces rather than engine power.

Think of autorotation like a maple seed falling from a tree—the spinning motion creates lift that slows the descent. In a helicopter, the rotor disc is divided into three regions:

• Driven region (outer 30%): Produces drag, tends to slow rotor
• Driving region (middle 40%): Produces thrust that drives the rotor system
• Stall region (inner 30%): Produces drag due to high angles of attack

Energy management is critical—you have two forms of stored energy: altitude (potential energy) and rotor RPM (kinetic energy). Converting altitude to rotor RPM during descent, then converting rotor RPM to lift during flare is the fundamental energy exchange.

Effects of Environmental Factors (PH.VI.C.K1)

Wind Effects: Headwinds decrease ground speed and extend glide distance. Tailwinds increase descent rate and reduce glide distance. Crosswinds require drift correction but complicate energy management during turns.

Weight: Heavier helicopters have higher descent rates but carry more kinetic energy. Light helicopters autorotate at slower airspeeds but have less energy for the flare.

Temperature and Density Altitude: High density altitude reduces rotor efficiency and increases autorotative descent rate. True airspeed increases while indicated airspeed remains constant, affecting energy available for flare.

Rotor RPM Management (PH.VI.C.K2)

Maintaining proper rotor RPM is critical for autorotational success. Normal autorotation RPM is typically 90-100% of normal operating RPM. Low RPM reduces available energy for flare and increases stall risk. High RPM may exceed limitations and cause structural damage.

Use collective to control rotor RPM: Lower collective to increase RPM, raise collective to decrease RPM. Aft cyclic also helps maintain RPM by reducing rotor disc angle of attack.

Descent Rate Management (PH.VI.C.K4)

High descent rates result from:

• Excessive collective pitch
• Low rotor RPM
• High density altitude
• Turbulence
• Improper airspeed

Excessive descent rates consume altitude rapidly, reduce flare capability, and increase ground impact forces. Monitor vertical speed indicator and adjust collective/airspeed as needed.

Bank Angle and Airspeed Effects (PH.VI.C.K5)

Steeper bank angles increase load factor and descent rate. Bank angles beyond 30 degrees significantly increase energy consumption. Maintain minimum bank angle necessary for desired turn radius.

Airspeed directly affects glide performance. Too slow increases descent rate and reduces control authority. Too fast may exceed glide distance to landing area and complicates energy management for flare.

Risk Management Factors

Low Entry Altitudes (PH.VI.C.R1): Practice autorotations require minimum 500 feet AGL for safe power recovery. Lower altitudes leave insufficient time for proper technique development and increase risk of forced landing.

Flight Control Inputs (PH.VI.C.R2): Abrupt or excessive control inputs can cause rotor RPM fluctuations, altitude loss, or loss of control. Use smooth, deliberate inputs throughout the maneuver.

Turbulence and Wake Turbulence (PH.VI.C.R3, PH.VI.C.R4): Turbulence causes airspeed and rotor RPM fluctuations, complicating energy management. Windshear can dramatically change descent rate and glide path. Choose smooth air conditions for training.

Energy Management (PH.VI.C.R5): Poor energy management leads to low rotor RPM, excessive descent rates, or inability to flare effectively. Conservative collective use preserves energy for the critical flare phase.

Main Rotor Speed (PH.VI.C.R6, PH.VI.C.R7): Low rotor RPM reduces control authority and available flare energy. Rotor stall occurs when retreating blade angle of attack exceeds stall angle, causing severe vibration and control loss.

Excessive Descent Rate (PH.VI.C.R9): High descent rates indicate energy mismanagement and reduce options for safe termination. Monitor VSI continuously and correct promptly.

Powerplant Failure During Maneuver (PH.VI.C.R10): During practice autorotations, actual engine failure requires immediate transition from practice to emergency procedures. Maintain autorotational flight and prepare for actual landing.

Rolling Out of Turns (PH.VI.C.R11): Late or improper rollout leads to overshoot or undershoot of landing area. Plan rollout to align with landing area while maintaining energy management.

Collision Hazards (PH.VI.C.R12): Maintain visual scanning throughout maneuver. Other aircraft may not see descending helicopter. Announce intentions on appropriate frequency.

Termination Procedures (PH.VI.C.R13, PH.VI.C.R14): Improper power application during recovery can cause rotor overspeed or loss of control. Smooth, progressive power application prevents dynamic rollover or settling with power.

Task Management (PH.VI.C.R15): Autorotations require simultaneous management of multiple parameters. Prioritize flight path control, rotor RPM, then landing area alignment. Avoid fixation on single instrument or reference.

Autorotation with Turns Procedure

1. Complete appropriate checklist - Use emergency checklist or training checklist as appropriate
2. Clear the area - Ensure no conflicting traffic in practice area
3. Select suitable landing area - Identify clear area within gliding distance
4. Select appropriate entry altitude - Minimum 1,000 feet AGL for training
5. Make radio calls - Announce practice autorotation on appropriate frequency
6. Initiate at proper point - Begin when landing area is 30-45 degrees behind
7. Establish autorotation - Lower collective, apply aft cyclic, maintain rotor RPM
8. Execute turn - Use coordinated bank and rudder to track toward landing area
9. Manage energy - Balance airspeed, rotor RPM, and descent rate
10. Roll out on final approach - Complete turn no lower than 300 feet AGL
11. Initiate power recovery - Smooth power application coordinated with collective

Schedule

Equipment

Required References

• FAA-H-8083-21B Helicopter Flying Handbook, Chapter 11
• FAA-S-ACS-15 Private Pilot Helicopter Airman Certification Standards
• Pilot’s Operating Handbook for specific helicopter model
• 14 CFR Parts 61 and 91
• ASA Helicopter Oral Exam Guide (Ryan Dale)

Materials and Visual Aids

• Helicopter autorotation diagram showing rotor disc regions
• Energy management chart (altitude vs. rotor RPM)
• Height-velocity diagram for specific aircraft
• Practice area sectional chart with emergency landing sites marked
• Emergency checklist cards
• Whiteboard or tablet for diagramming

Required Equipment

• Dual-control training helicopter
• Aviation headsets with intercom
• Current sectional charts
• Aircraft documents and POH
• First aid kit and emergency equipment

Instructor Actions

1. Brief student on lesson objectives and autorotation with turns theory, emphasizing that this maneuver combines energy management with flight path control to reach a specific landing area.

2. Demonstrate rotor disc regions using visual aid, explaining how upward airflow through driving region powers the rotor system during autorotation.

3. Review energy management principles: “You’re trading altitude for rotor RPM during descent, then trading rotor RPM for lift during the flare—it’s like a bank account where you save energy for when you need it most.”

4. Explain environmental effects on autorotation performance, emphasizing how density altitude and weight affect descent rate and available flare energy.

5. Review all risk management items systematically, relating each to previous student experiences or scenarios.

6. Demonstrate proper radio calls for practice autorotations, emphasizing the need to announce position and intentions clearly.

7. Show student how to select appropriate landing areas from altitude, considering wind direction, obstacles, and approach path.

8. Perform complete demonstration autorotation with turns, narrating each step: entry, collective lowering, rotor RPM management, turn execution, energy management, and power recovery.

9. Emphasize rotor RPM control throughout the maneuver: “Feel that gentle back pressure on the collective—we’re not pulling, just maintaining light pressure to keep the RPM in the green.”

10. Demonstrate coordinated turn techniques in autorotation, showing how bank angle affects descent rate and energy consumption.

11. Guide student through first practice attempt, providing verbal coaching for rotor RPM, airspeed, and turn coordination.

12. Monitor student for common errors: excessive collective movement, uncoordinated turns, poor energy management, late rollout from turns.

13. Provide immediate feedback on each attempt: “Good rotor RPM control, but let’s work on shallower bank angles to preserve energy.”

14. Demonstrate power recovery technique, emphasizing smooth, progressive power application coordinated with collective pitch changes.

15. Debrief each autorotation immediately after power recovery, highlighting positive aspects and areas for improvement.

Student Actions

1. Review lesson objectives and ask questions about autorotation theory and energy management principles.

2. Demonstrate understanding of rotor disc regions and explain how autorotation differs from powered flight.

3. Identify and discuss risk factors associated with autorotation with turns, relating to previous training experience.

4. Practice radio phraseology for announcing practice autorotations in the practice area.

5. Complete aircraft preflight inspection with emphasis on items critical to autorotation training (flight controls, rotor system, engine instruments).

6. Observe instructor demonstration carefully, noting control inputs, instrument indications, and visual references.

7. Perform practice autorotations with turns under instructor guidance, demonstrating proper:

   • Entry technique with collective lowering and aft cyclic
   • Rotor RPM control throughout the maneuver
   • Coordinated turn execution with appropriate bank angles
   • Airspeed control within ±10 knots of best autorotation speed
   • Energy management to maintain safe descent rate

8. Execute coordinated turns to track toward designated landing areas while maintaining autorotational flight parameters.

9. Roll out of turns no lower than 300 feet AGL, aligned with the approach path to the selected landing area.

10. Demonstrate proper power recovery technique with smooth collective and power coordination.

11. Maintain situational awareness throughout each autorotation, scanning for traffic and monitoring aircraft systems.

12. Self-critique performance after each attempt, identifying areas for improvement in energy management and flight path control.

13. Demonstrate ability to terminate autorotation to stabilized hover position within 200 feet of designated point.

Completion Standards

The student demonstrates satisfactory performance when able to accomplish the following elements of FAA-S-ACS-15 PH.VI.C:

PH.VI.C.S1: Complete the appropriate checklist(s) promptly and accurately, using either emergency or training autorotation checklist as appropriate for the scenario.

PH.VI.C.S2: Make clear, professional radio calls announcing practice autorotations, including aircraft identification, position, and intentions.

PH.VI.C.S3: Select suitable landing areas from altitude that are within gliding distance, free of obstacles, and appropriate for helicopter operations.

PH.VI.C.S4: Clear the practice area systematically, checking for conflicting traffic before initiating each autorotation.

PH.VI.C.S5: Select appropriate entry altitudes of at least 1,000 feet AGL for training autorotations, allowing adequate altitude for safe power recovery.

PH.VI.C.S6: Initiate the maneuver at the proper point relative to the selected landing area, typically when the area is 30-45 degrees behind the aircraft.

PH.VI.C.S7: Establish and maintain power-off glide with autorotation airspeed within ±10 knots of manufacturer’s recommended speed, with helicopter properly trimmed.

PH.VI.C.S8: Maintain main rotor RPM within normal operating limits throughout the maneuver, demonstrating proper collective control and energy management.

PH.VI.C.S9: Execute coordinated turns as necessary to track toward the selected landing area, avoiding undershoot or overshoot of the intended touchdown point.

PH.VI.C.S10: Roll out of all turns no lower than 300 feet AGL while aligned with the flight path to the selected landing area.

PH.VI.C.S11: Use proper deceleration and collective pitch application that permits safe clearance between the aircraft tail boom and surface, demonstrating understanding of flare timing and technique.

PH.VI.C.S12: Initiate proper power recovery with smooth, coordinated application of collective pitch and engine power to prevent rotor overspeed or loss of control.

PH.VI.C.S13: Terminate autorotation to a stabilized hover within 200 feet of the designated point, demonstrating precise energy management and control coordination.

The student must also demonstrate comprehensive understanding of all knowledge elements (PH.VI.C.K1-K5) and proper management of all identified risk factors (PH.VI.C.R1-R15) throughout the maneuver performance.