Powerplant Failure at Altitude in a Single-Engine Helicopter

Objective

By the completion of this lesson, the commercial helicopter pilot applicant will demonstrate the ability to recognize and respond to a powerplant failure at altitude by establishing and maintaining a proper autorotation, selecting an appropriate landing area, managing energy throughout the descent, and executing a power recovery at a safe altitude while maintaining main rotor RPM within normal limits and establishing autorotation airspeed ±5 knots, consistent with the performance standards of FAA-S-ACS-16, Area of Operation VIII, Task B (CH.X.B).

Content

Powerplant Failure at Altitude Overview

Powerplant failure at altitude in a single-engine helicopter requires immediate recognition and response to establish an autorotation. Unlike the private pilot who demonstrates basic autorotation competency, the commercial pilot must exhibit precision, consistent energy management, and professional decision-making throughout the maneuver. This skill forms the foundation of emergency procedures that may save lives and aircraft.

An autorotation is a controlled descent of a helicopter in which the main rotor is driven solely by aerodynamic forces rather than engine power. When engine power is lost, the upward flow of relative wind through the rotor system maintains rotor RPM, storing kinetic energy that can be converted to lift during the flare and touchdown phases.

Elements of Powerplant Failure at Altitude

Recognition: The first indication of powerplant failure may be:

• Sudden yaw due to loss of torque (opposite the direction of normal flight yaw)
• Low rotor RPM horn/warning
• Illumination of warning lights
• Unusual engine noises, vibrations, or smells
• Loss of manifold pressure indication

Immediate Actions: Memory items that must become instinctive:

1. Lower collective immediately and smoothly to maintain rotor RPM
2. Apply appropriate pedal to counteract yaw and maintain heading
3. Establish autorotation airspeed (typically 60-70 KIAS for most training helicopters, but consult POH/RFM)
4. Trim helicopter as needed

Analysis Phase: Once the helicopter is stabilized:

• Attempt restart if time and altitude permit (follow manufacturer’s procedures)
• Declare emergency with ATC if able (“Mayday, Mayday, Mayday”)
• Squawk 7700 on transponder
• Begin planning for landing area selection

Main Rotor RPM (Nr) Management

Main rotor RPM is the single most critical parameter in autorotation—without sufficient rotor RPM, you cannot complete a successful flare and touchdown.

Normal Operating Range: Most training helicopters operate in the green arc (typically 90-110% Nr). During autorotation, you must maintain Nr within limits, which typically means keeping the needle in the green arc. The POH/RFM specifies exact limits.

Factors Affecting Rotor RPM:

Collective Position: Lowering collective decreases blade pitch angle, reducing drag and allowing Nr to increase. Raising collective increases blade pitch, increasing drag and decreasing Nr. The initial lowering of collective during power failure recognition is critical—delay causes rapid rotor RPM decay.

Airspeed: The faster the helicopter descends through the air, the greater the upward flow of relative wind through the rotor system. Each helicopter has an optimal autorotation airspeed that provides the best balance between rotor RPM sustainability and descent rate.

Rotor Disc Angle: Cyclic inputs change the rotor disc’s angle relative to the relative wind. Aggressive maneuvering can cause rotor RPM fluctuations requiring collective corrections.

Effects of Environmental and Aircraft Conditions

Weight: Heavier helicopters descend faster in autorotation. Increased weight means increased inertia, requiring more energy (rotor RPM) to arrest descent during flare. Heavier helicopters also have higher minimum autorotation airspeeds. A Robinson R22 at gross weight versus light weight demonstrates noticeably different descent rates and landing characteristics.

Density Altitude: High density altitude (hot, high, humid conditions) reduces air density. In autorotation, this means:

• Faster descent rates for the same indicated airspeed
• Less aerodynamic efficiency of rotor blades
• Reduced effectiveness of flare
• Greater true airspeed for same indicated airspeed, increasing ground distance covered

Think of density altitude like running through water versus air—the thinner air provides less resistance and less “bite” for the rotor blades.

Wind:

Headwind: Reduces groundspeed, decreases landing distance required, allows steeper approach angles. Preferred for autorotations.

Tailwind: Increases groundspeed significantly, increases landing distance, reduces time available for flare. Avoid tailwind autorotations when possible—the ground rush during final approach is substantial and spatial disorientation risk increases.

Crosswind: Requires drift correction during descent and adds complexity to final approach. May necessitate landing with lateral drift if wind is strong.

Temperature: Cold temperatures increase air density (opposite of density altitude effect), providing better rotor efficiency and slower descent rates. Hot temperatures degrade performance. The commercial pilot must mentally adjust expectations based on current conditions—what worked on a cool morning may require different technique on a hot afternoon.

Energy Management in Autorotation

Energy management is the hallmark of professional autorotation technique. You have three forms of energy available:

1. Potential Energy (Altitude): Height above ground. This is your primary energy reserve. Once spent, it’s gone.

2. Kinetic Energy - Translational (Airspeed): Forward speed through the air. Can be converted to rotor RPM or altitude through cyclic flare.

3. Kinetic Energy - Rotational (Rotor RPM): Stored in the spinning rotor system. This is your emergency savings account—converted to lift during flare and cushioned touchdown.

Energy Management Strategy:

During descent, maintain optimal autorotation airspeed (per POH) to achieve the best glide ratio—maximum forward distance per unit of altitude lost. This preserves options for landing site selection.

Never sacrifice rotor RPM to gain airspeed or altitude—rotor RPM is irreplaceable in the final seconds of the maneuver. If Nr begins decaying, lower collective immediately.

The height-velocity diagram (14 CFR 91.119 notwithstanding for helicopters) shows combinations of height and airspeed from which a safe landing may not be possible. The shaded “avoid” areas represent insufficient altitude to establish autorotation or insufficient energy to arrest descent. Commercial operations frequently require flight in these areas (14 CFR 133, 136, 137), making autorotation proficiency absolutely critical.

Causes and Effects of High Descent Rates

Causes:

• Airspeed too slow or too fast (off the “back side” of the power curve)
• Excessive collective raised during descent (attempting to “stretch” the glide)
• High density altitude
• Heavy gross weight
• Low rotor RPM
• Steep bank angles during maneuvering

Effects:

• Reduced time for planning and maneuvering
• Increased vertical velocity requiring aggressive flare
• Greater risk of hard landing or dynamic rollover
• Reduced margin for error in landing site selection
• Potential to exceed Vne in powered recovery

High descent rates develop insidiously. A commercial pilot monitors vertical speed indicator continuously and cross-checks with visual cues (parallax of landmarks). If descent rate increases unexpectedly, check airspeed, rotor RPM, and collective position immediately.

Effects of Varying Bank Angles, Airspeeds, and Rotor RPM

Bank Angles: Any bank increases the load factor on the rotor system. In autorotation, increasing load factor requires increased rotor RPM to maintain altitude—but you’re descending, not maintaining altitude, so increased load factor increases descent rate.

• Shallow banks (15° or less): Minimal descent rate increase, acceptable for small corrections
• Moderate banks (15-30°): Noticeable descent rate increase, useful for more aggressive maneuvering but requires monitoring
• Steep banks (30°+): Significant descent rate increase, potential rotor RPM decay, increased risk of loss of control

Limit bank angles during autorotation. Plan turns early and execute them smoothly. Commercial pilots don’t wait until low altitude to maneuver.

Airspeeds:

Below Optimal: Increased descent rate, reduced forward distance capability, operating on the “back side” of the power curve where increased pitch requires increased power (which you don’t have). Recovery requires lowering nose, which initially increases descent rate further.

Optimal (per POH): Best glide ratio, manageable descent rate, maximum distance capability. This is where you should stabilize for the majority of the descent.

Above Optimal: Increased descent rate, risk of exceeding power-off Vne, reduced time to landing site. However, excess airspeed can be converted to rotor RPM and altitude during flare—some pilots intentionally carry extra airspeed in the final 200-300 feet.

Rotor RPM Variations:

Low Nr: Reduced rotor efficiency, increased descent rate, inadequate energy storage for flare, risk of blade stall, potential for low-G condition if recovery attempted abruptly. If Nr drops below green arc, lower collective immediately—this is non-negotiable.

High Nr: Risk of exceeding maximum rotor RPM (usually 110-115% Nr), potential blade damage, potential overspeed during powered recovery. If Nr enters red arc, raise collective slightly to increase blade drag.

Optimal Nr: Mid to upper green arc. Provides maximum stored energy with margin below red line.

Autorotation Power-Off Vne Limitation

Power-off Vne is lower than normal Vne in many helicopters. Check POH/RFM Section 2 (Limitations). For Robinson R22, power-off Vne is 100 KIAS versus normal Vne of 102 KIAS—small margin. Exceeding power-off Vne during autorotation risks structural damage, particularly to tail rotor driveshaft and related components which may be unloaded or operating in unfamiliar conditions without engine torque.

During powered recovery, accelerating through power-off Vne is acceptable because power is being applied, but never exceed normal Vne.

Landing Area Selection

Altitude Considerations: Higher altitude provides more time for evaluation and maneuvering. From 3,000 AGL, you can glide approximately 1.5-2.5 nautical miles depending on helicopter type, weight, and conditions. Use this time wisely.

The 5 S’s of Landing Site Selection:

1. Size: Must accommodate rotor diameter with margins for approach angle, flare, and any drift. Minimum of 2x rotor diameter, preferably larger.

2. Shape: Rectangular areas allow aligned approaches. Irregular shapes may force crosswind landings or offset approaches.

3. Surface: Firm enough to support skids without rollover risk. Evaluate for:

   • Slope (level preferred, maximum 5-7° in most training helicopters)
   • Obstacles (wires, fences, ditches)
   • Surface material (concrete/asphalt best, tall grass obscures obstacles, water depth unknown)

4. Surroundings: Approach path must be clear. Evaluate obstacles on all sides—you may need to maneuver after committing to a site.

5. Suitability: Consider winds, sun position, populated areas (14 CFR 91.119), emergency services access, and the fact that you’ll need to secure the helicopter and possibly stay with it.

Decision Point: Select primary landing area by 1,000 AGL. Identify alternate by 500 AGL. Below 500 AGL, you’re committed to maneuvering to your selected site—changing plans at low altitude is high risk.

Wind Assessment: Use smoke, flags, water surfaces, tree movement, or forecasted winds. Always attempt to land into the wind when possible. A 10-knot tailwind triples your ground roll distance and approach difficulty.

Maneuvering to Selected Area

High Key Position: Not formally defined for autorotations like it is for military patterns, but conceptually: position yourself upwind and offset from intended landing area at 1,000-1,500 AGL. From here, you can maneuver to a modified base leg.

Energy Management: Maintain autorotation airspeed and rotor RPM. Avoid steep banks. Make 90° turns rather than continuous spirals when possible—easier to judge wind drift and landing spot alignment.

Overshooting vs. Undershooting:

Overshooting: You’ll pass beyond the landing area. Correct by:

• S-turning to lose ground distance (increases descent due to maneuvering)
• Slipping (not recommended in helicopters due to main rotor/tail rotor interaction)
• Accepting alternate landing area further along track

Undershooting: Won’t reach landing area. Correct by:

• Increasing airspeed slightly (trades altitude for distance, increases descent rate)
• Reducing maneuvering (fly more direct)
• Selecting closer alternate site

Professional pilots plan conservatively—better to overshoot and have options than undershoot and run out of ideas at 50 feet.

Radio Communications

Initial Call (if time permits): “[Facility], [Call Sign], Mayday, Mayday, Mayday, engine failure, autorotating, [location], [POB].”

Example: “Phoenix Approach, Helicopter 123AB, Mayday Mayday Mayday, engine failure, autorotating 10 miles north of Deer Valley Airport, 2 people on board.”

Squawk 7700 on transponder immediately if able.

Follow-up: If altitude and workload permit: “Helicopter 123AB, landing [location description], requests emergency services.”

Remember: Aviate, Navigate, Communicate—in that order. Fly the helicopter first. If you’re single-pilot with high workload, radio calls are lowest priority. However, making calls early (above 1,500 AGL when stabilized) costs little and benefits greatly.

Powered Recovery Technique

The powered recovery demonstrates your ability to recognize an appropriate recovery altitude and smoothly coordinate all controls to return to powered flight.

Initiation Altitude: Evaluator will specify, typically 500-1,500 AGL for training. In real emergencies, full-touchdown autorotation is the goal unless engine restart succeeds.

Recovery Procedure:

1. Announce: “Recovering with power at [altitude].”

2. Throttle: Smoothly roll throttle from closed to flight idle position, correlating engine and rotor RPM. In governor-equipped helicopters, return governor to ON.

3. Collective: As engine RPM increases and clutch engages, smoothly raise collective to maintain altitude. Coordinate collective increase with throttle movement—adding power before clutch engagement or adding collective before power arrives causes rotor RPM decay.

4. Pedal: Apply pedal to maintain heading as torque builds. Right pedal in American helicopters (counterclockwise rotor rotation).

5. Cyclic: Maintain or reduce airspeed as appropriate, transition to level flight attitude.

6. Monitor: Watch rotor RPM, engine RPM, and torque throughout recovery. If Nr drops, lower collective immediately. If Nr increases excessively, raise collective smoothly.

Common Errors:

• Adding collective before power arrives (rotor RPM decay)
• Adding power too aggressively (over-torque, engine overspeed)
• Failing to coordinate pedal inputs (heading deviation)
• Fixating on one instrument (loss of situational awareness)
• Initiating recovery too low (insufficient altitude for procedure)

Risk Management Elements

Low Entry Altitudes: Beginning autorotation training below 1,500 AGL reduces time available for analysis and recovery. Commercial pilots should enter autorotations from 1,500+ AGL in training, providing adequate margin for the entire maneuver. Real emergencies don’t choose altitude, but training scenarios should maximize safety.

Flight Control Inputs: Abrupt or excessive control inputs destabilize the helicopter and waste energy. Specific risks:

• Abrupt aft cyclic: Low-G condition, potential mast bumping (semi-rigid rotor systems)
• Abrupt collective changes: Rotor RPM fluctuations
• Excessive bank angles: Increased descent rate, potential loss of control
• Over-controlling with pedals: Yaw oscillations, heading deviations

Use smooth, coordinated, measured inputs. Think “firm and positive” rather than “aggressive.”

Turbulence and Wake Turbulence: Turbulence disrupts rotor RPM and helicopter stability. In autorotation, you have no power reserve to compensate. Avoid areas of known turbulence if altitude permits (route around, avoid ridge lines, stay away from heavy jet paths). If encountered:

• Maintain rotor RPM as primary concern
• Accept altitude/heading deviations rather than fighting turbulence
• Consider increasing airspeed slightly for better stability

Wake turbulence from fixed-wing aircraft or other helicopters can be catastrophic in autorotation. Maintain spacing—wait for wake to dissipate or route around departure/arrival paths.

Windshear: Sudden wind changes alter airspeed and rotor RPM. Particularly dangerous at low altitude during approach phase. Indications include:

• Sudden airspeed changes without control inputs
• Uncommanded altitude changes
• Difficulty maintaining rotor RPM
• Visual cues of wind shift (rain shafts, dust, wave patterns)

If windshear encountered in autorotation, prioritize rotor RPM above all else. Accept landing area changes if necessary.

Low Rotor RPM or Rotor Stall: Low rotor RPM is the most critical emergency within an emergency. If Nr drops below approximately 80%, rotor stall may occur—blades exceed critical angle of attack, lose lift catastrophically, and helicopter drops uncontrollably.

Prevention:

• Lower collective immediately at engine failure recognition
• Monitor Nr continuously throughout descent
• Never raise collective to “stretch” glide or reduce descent rate unless Nr is excessive
• Avoid high bank angles
• Maintain proper airspeed

Recovery (if time permits):

• Lower collective fully and immediately
• Level wings
• Allow Nr to recover before attempting any other correction
• If Nr does not recover, touchdown may be uncontrolled—protect head, maintain level attitude if possible

Powerplant Failure During the Maneuver (Practice): If engine actually fails during practice autorotations:

• Recognize it (no change in helicopter behavior—already in autorotation)
• Announce to instructor: “Actual engine failure”
• Continue autorotation to full touchdown or suitable recovery altitude
• Do not attempt restart below 500 AGL
• Use emergency procedures for full autorotation

This scenario is rare but possible (carburetor icing, fuel contamination, mechanical failure).

Collision Hazards: During autorotation, you’re focused inside and below. Specific collision risks:

• Other aircraft (maintain clearing procedures throughout)
• Birds (especially during hunting/gliding descent)
• Wires (single greatest helicopter collision hazard—difficult to see, often in intended landing areas)
• Ground obstacles (towers, vehicles, people in selected landing areas)

Maintain scanning pattern: instrument check, landing area ahead, sides for obstacles, instruments, visual scan. Never fixate.

Helicopter Trim: Out-of-trim helicopters require continuous control input, increasing pilot workload and reducing precision. Trim helicopter in autorotation descent once stabilized—usually slight right cyclic and aft cyclic trim, varies by helicopter type. Trimming is professional technique that frees attention for planning and situational awareness.

Distractions, Task Prioritization, Loss of Situational Awareness, or Disorientation: Autorotation is high workload. Distractions include:

• Passenger reactions
• Radio calls
• Checklist attempts
• Troubleshooting engine failure
• Fixation on single task (landing site selection tunnel vision)

Task Prioritization: Use the “bold face/checklist” concept. Bold face items are memory items done immediately:

1. Maintain rotor RPM (lower collective)
2. Establish autorotation
3. Trim helicopter
4. Select landing area

Everything else—radio calls, restart attempts, checklist reviews—is secondary. If task saturated, abandon lower-priority items.

Situational Awareness: Mental model of your position, altitude, energy state, landing area location, and wind. Loss of situational awareness signs:

• Uncertainty about position
• Surprise at altitude loss rate
• Confusion about wind direction
• Inability to locate selected landing area

Prevent by verbalizing key points: “1,500 feet, on glide path, landing area 11 o’clock, wind from the south, rotor RPM green arc.”

Spatial Disorientation: Rare in daytime VFR autorotations but possible in confined areas, over water, or unusual attitudes. Trust instruments if outside visual cues become unreliable.

Regulatory References

14 CFR §61.133 - Commercial Pilot Privileges and Limitations: Commercial pilots may act as PIC for compensation or hire. This includes operations where engine failure is statistically more likely (aerial observation, external load, patrol flying, flight instruction). Superior autorotation skills are essential for commercial privileges.

14 CFR §91.119 - Minimum Safe Altitudes: Helicopters may operate below specified altitudes if operated “without hazard to persons or property on the surface.” However, the height-velocity diagram in the helicopter POH/RFM establishes combinations of height and speed to avoid. Commercial pilots must balance operational requirements with safety.

14 CFR §91.3 - Responsibility and Authority of Pilot in Command: In an emergency, the PIC may deviate from any regulation to the extent required to meet that emergency (e.g., landing in prohibited areas, violating airspace). However, FAA may request written report.

Practical Exercise Standards

Per FAA-S-ACS-16, Commercial Pilot Helicopter ACS, the applicant must demonstrate autorotation entry at altitude with smooth coordination of all controls, establishment of proper autorotation airspeed ±5 knots, maintenance of rotor RPM in normal range throughout, appropriate landing area selection considering all relevant factors, maneuvering to avoid under/overshooting, radio calls as appropriate, and recovery with power at a safe altitude as directed.

Schedule

Equipment

Aircraft:

• Training helicopter (R22, R44, S300, or equivalent) airworthy for autorotation training
• Minimum 1,500 AGL altitude capability
• Intercom system functional
• Adequate fuel for 1.5 hours flight with reserve

Required References:

• FAA-S-ACS-16, Commercial Pilot – Rotorcraft Helicopter Airman Certification Standards (current edition)
• FAA-H-8083-21B, Rotorcraft Flying Handbook
• Helicopter Pilot Operating Handbook / Rotorcraft Flight Manual for aircraft used
• FAA-AC 61-140, Autorotation Training
• Current sectional chart for practice area
• FAA Airplane Flying Handbook FAA-H-8083-3 (Chapter 3 for energy management concepts, if needed)

Instructor Materials:

• Commercial Pilot Helicopter ACS with Task CH.X.B highlighted
• Lesson plan with completion standards checklist
• Student training record/logbook
• Visual aids:
  • Height-velocity diagram for aircraft type
  • Autorotation profile diagram showing entry, descent, flare, and recovery phases
  • Rotor RPM management diagram
  • Landing area selection criteria card (5 S’s)

Student Materials:

• Headset
• Current medical certificate
• Private pilot helicopter certificate
• Photo ID
• Logbook
• Sectional chart
• Aircraft POH/RFM
• ACS (student should have own copy)
• Kneepad and pen

Safety Equipment:

• Fire extinguisher (in aircraft)
• First aid kit (in aircraft)
• Operable ELT
• Cell phone or radio for ground communication if landing off-airport occurs

Instructor Actions

1. Pre-flight briefing on ground: Explain that today’s lesson focuses on powerplant failure at altitude, distinguishing it from private pilot training by emphasizing the commercial standards of ±5 knots airspeed tolerance, consistent rotor RPM management, and professional decision-making. Review the objective: student will demonstrate autorotations to ACS commercial standards by end of lesson.

2. Present energy management concept using the “energy bank account” analogy: “You have three forms of energy in autorotation—altitude is your savings account, airspeed is your checking account, and rotor RPM is cash in your wallet. You can transfer between accounts, but you can’t create money out of thin air. Once you spend your rotor RPM, you’re broke and can’t write any more checks. We manage these accounts to ensure we always have cash when we need it—at touchdown.”

3. Demonstrate rotor RPM management on whiteboard or tablet: Draw rotor tachometer with green arc, yellow caution arc (if applicable), and red line. Mark normal operating range and explain that collective is the primary rotor RPM control in autorotation. Show cause-effect: collective down = RPM up, collective up = RPM down. Emphasize immediate collective lowering at engine failure recognition.

4. Review the memory items for engine failure: “These must become instinctive—lower collective, maintain rotor RPM, establish autorotation airspeed, trim. Say them out loud: lower collective, maintain rotor RPM, establish autorotation, trim. In the aircraft, you’ll verbalize these during the first practice.”

5. Explain effects of weight, temperature, and density altitude using student’s real-world experience: “Think about the difference between a hot afternoon at 5,000-foot field elevation versus a cool morning at sea level. The hot, high conditions give you thinner air—less bite for the rotor blades. You’ll descend faster, and your flare will be less effective. Today we’re at [current conditions], so expect [faster/slower] descent rate than you might have seen in different conditions.”

6. Discuss landing area selection using sectional chart of practice area: Point out potential emergency landing sites visible from planned altitude—fields, roads, clearings. Apply the 5 S’s criteria to each. “This field here looks good—adequate size, rectangular shape, appears firm surface based on coloring, surrounded by low vegetation, and suitable in that it’s away from populated areas. Compare that to this area—too many trees surrounding it, limiting approach paths.”

7. Brief risk management items specific to today’s flight: “We’ll enter autorotations from minimum 2,000 AGL, giving us adequate margin. I’ll handle throttle closure initially until I observe your timing is appropriate. Watch for wake turbulence if we’re following other traffic to the practice area. If rotor RPM drops below 90%, remember: lower collective immediately—nothing else matters. If I say ‘I have the controls,’ release immediately and put your hands in sight.”

8. Conduct standard preflight inspection with student, emphasizing engine compartment, oil level, fuel quantity and quality, rotor system security, tail rotor drive system, and control continuity. “In autorotation training, we’re asking the rotor system to do its job without engine support. Any deficiencies in rotor blades, dampers, or hub components are amplified.”

9. During taxi and hover check, verify all engine instruments in normal range: “Confirm engine temps, pressures, and governor operation now—we want no surprises when we simulate failure.”

10. Depart practice area and climb to 3,000 AGL minimum, establishing level cruise flight at normal airspeed. Clear area thoroughly—two 90° clearing turns. “Before every autorotation, we clear the area systematically. Other traffic may not expect a helicopter descending rapidly.”

11. Demonstrate first autorotation with full narrative: “Watch and listen—I’ll talk through every action. We’re at 3,000 feet, trimmed, 70 knots. Clearing left, clearing right, clear below. Simulated engine failure—throttle rolling to idle, lowering collective smoothly and immediately, rotor RPM coming up to mid-green. Applying left pedal to counteract yaw—nose wants to go right when power is lost. Establishing 60 knots—our best autorotation airspeed per the POH. Trimming helicopter—slight right cyclic, slight aft cyclic. Now I’m stabilized. Rotor RPM in green arc, 60 knots, descending 1,200 feet per minute. Selecting landing area—that field at 12 o’clock, rectangular, firm surface, clear approaches. Making shallow right turn to align. Monitoring rotor RPM—if it drops, I lower collective. At 1,500 feet, verifying my landing area is still suitable. At 1,000 feet, evaluator would direct recovery, so I’m announcing: ‘Recovering with power at 1,000 feet.’ Throttle rolling on smoothly, waiting for clutch engagement—feel it grab—collective coming up to maintain altitude, right pedal to counteract torque, adjusting cyclic to maintain heading and return to cruise attitude. Recovery complete, 1,000 feet, level flight.”

12. Debrief demonstration: “What did you observe about my timing on lowering collective? [Student responds.] Exactly—instantaneous. The quicker you lower collective, the less rotor RPM decay you experience. What happened to the nose when I reduced power? [Student responds.] Right—yawed to the right because of loss of torque reaction. Required immediate left pedal.”

13. Position helicopter for student’s first practice autorotation: “You have the controls. Let’s set up at 2,500 AGL, 70 knots, trimmed for level cruise. Clear the area with two 90-degree turns, and I’ll call ‘simulated engine failure’ when you’re ready.”

14. Call “simulated engine failure” after student completes clearing turns: “Simulated engine failure now.” [Instructor simultaneously rolls throttle to idle/flat pitch on correlator or as appropriate for aircraft type.]

15. Observe student’s initial response—evaluate collective lowering, pedal coordination, rotor RPM response: If student hesitates on collective, state firmly: “Collective down now.” If rotor RPM drops below 90%: “Lower collective—rotor RPM first priority.”

16. Coach student through establishing autorotation airspeed: “Forward cyclic to 60 knots—watch your airspeed indicator. Trim the helicopter now—less work, more focus on planning.”

17. Prompt landing area selection: “By now you should be selecting your landing area. What do you see as options?” [Student responds.] “Good choices. Pick one and commit. Where’s the wind from?” [Student responds.]

18. Monitor student’s scan pattern: If student fixates inside: “Look outside—check your landing area position.” If student fixates outside: “Check rotor RPM—don’t neglect your instruments.”

19. Provide energy management coaching: “You’re drifting right of your landing area—slight left turn. Watch your bank angle—too steep costs altitude and rotor RPM. Good correction. You’re tracking toward your spot now.”

20. At 1,500 AGL, assess student’s position and announce: “Continue to 1,000 feet for recovery or I’ll call it earlier if needed.”

21. At approximately 1,000 AGL or appropriate altitude for conditions, direct recovery: “Recover with power now.” [Instructor monitors student’s recovery technique.]

22. Evaluate power recovery: Watch for coordination of throttle advance, collective increase timing, pedal application, and rotor RPM management. If student adds collective before power arrives: “Power first, then collective—you just decreased rotor RPM. Let’s discuss that.”

23. After recovery to level flight, conduct immediate debrief while maneuvering for next setup: “Good initial collective lowering. Your airspeed was 63 knots—within tolerances but let’s aim for 60 exactly. Rotor RPM stayed mid-green throughout—excellent. Your landing area selection was appropriate, but you started maneuvering late. Next time, select by 1,500 feet and start your turn earlier. Power recovery was smooth but you added a bit too much collective initially—small corrections. Ready for another?”

24. Conduct second and third autorotations with progressively less coaching: Transition from directive (“lower collective now”) to questioning (“what’s your rotor RPM doing?”) to silent observation.

25. Introduce variations in subsequent autorotations: Different entry airspeeds (70 knots, 80 knots—within normal flight envelope), different entry altitudes (2,000 vs 3,000 AGL), different landing area selections requiring more maneuvering.

26. Hover for ground break after 3-4 autorotations: “We’ll hover here for a moment. How did that last one feel? [Student responds.] Let’s talk about your maneuvering—you used steeper bank angles than necessary, which increased descent rate. Shallow banks early give you better energy management. Also, you’re doing well on rotor RPM, but watch your outside scan—I noticed you were focused primarily on instruments. We need balance.”

27. Continue practice emphasizing weak areas: If student struggles with rotor RPM: focus on collective discipline. If landing area selection is poor: discuss 5 S’s again and require verbalization of selection criteria. If maneuvering is excessive: emphasize early decisions.

28. During final practice autorotations, simulate commercial checkride environment: Provide minimal input, observe silently, take notes. Evaluate against ACS standards: airspeed ±5 knots, rotor RPM in limits, appropriate landing area selected, successful maneuvering without over/undershooting, proper radio calls, smooth power recovery.

29. If student demonstrates consistent ACS performance, introduce emergency radio call practice: “On the next one, make an actual radio call to [facility] declaring the emergency. Say ‘Practice autorotation for training’ at the end so they know it’s not real.”

30. Return to airport and debrief during taxi: “Overall, strong performance today. Your rotor RPM management is commercial-standard—stayed in green arc on every autorotation. Airspeed ranged from 58 to 65 knots—mostly within ±5 standard, and we’ll tighten that with practice. Landing area selection improved through the lesson—by the end, you were making decisions early and maneuvering efficiently.”

31. Conduct formal post-flight debriefing on ground after shutdown: Review each autorotation using notes. Identify specific improvements: “First autorotation: rotor RPM perfect, airspeed 63 knots, landing area selected late. Third autorotation: rotor RPM perfect, airspeed 60 knots exactly, landing area selected at 1,500 feet. You progressed well.”

32. Address risk management scenarios: “Let’s discuss what you’d do if rotor RPM started dropping during autorotation despite lowering collective. [Student responds.] Good—you’d check for hung-up collective, ensure you’re not in a steep bank, and verify airspeed is reasonable. If those are all correct and RPM still drops, you may have a rotor system failure—land as soon as possible.”

33. Review next lesson requirements: “Next time we’ll work on 180-degree autorotations, which require even tighter energy management. Before that lesson, review the POH section on height-velocity diagram and think about how autorotation technique changes when entering from lower altitudes. Questions about today?”

34. Complete student logbook entry: Record dual instruction time, maneuvers practiced, and note progress toward commercial ACS standards. Sign and date. “1.5 dual given. Commercial helicopter maneuvers: powerplant failure at altitude (CH.X.B). Student demonstrated autorotation entry, descent management, landing area selection, and powered recovery. Airspeed control ±5 knots, rotor RPM within limits. Progressing toward ACS standards.”

35. Assign supplemental study: “Read Rotorcraft Flying Handbook Chapter 11 on autorotations again, focusing on pages 11-5 through 11-9 concerning energy management. Also review AC 61-140. Be prepared to discuss how you’d handle an actual engine failure during pattern work—different considerations than at altitude.”

Student Actions

1. Arrive prepared with current medical certificate, private pilot certificate, logbook, and required materials. Review previous lesson notes and personal study of autorotation theory.

2. Participate in ground briefing by asking clarifying questions about energy management, landing area selection, and risk management items.

3. Demonstrate understanding of memory items by reciting them to instructor: “Lower collective, maintain rotor RPM, establish autorotation airspeed, trim.”

4. Explain effects of weight, temperature, and density altitude on autorotation performance when prompted by instructor.

5. Identify suitable emergency landing areas on sectional chart using 5 S’s criteria during briefing.

6. Conduct thorough preflight inspection with emphasis on engine, fuel system, and rotor system as directed by instructor.

7. Perform normal takeoff and departure to practice area while maintaining situational awareness of potential landing sites en route.

8. Observe instructor’s demonstration of complete autorotation, noting timing of control inputs, scan pattern, landing area selection process, and power recovery coordination.

9. Ask questions about demonstration to clarify any confusion about technique or sequencing.

10. Position helicopter at appropriate altitude and airspeed, trim for level flight, and complete clearing turns before each practice autorotation.

11. Execute immediate memory items when instructor calls “simulated engine failure”: Lower collective smoothly and immediately, apply appropriate pedal to maintain heading, establish autorotation airspeed.

12. Maintain rotor RPM in green arc throughout descent by making small collective adjustments as needed.

13. Establish autorotation airspeed of 60 knots ±5 knots (or POH-specified airspeed for aircraft type) and maintain throughout descent.

14. Trim helicopter to reduce control pressures and workload.

15. Select suitable landing area by 1,500 AGL using 5 S’s criteria, considering wind direction and personal limitations.

16. Announce landing area selection to instructor: “Landing in the rectangular field at 12 o’clock, wind from the south, clear approaches.”

17. Maneuver toward selected landing area using shallow bank angles (15° or less when possible), maintaining rotor RPM and airspeed throughout turns.

18. Monitor progress toward landing area and make corrections to avoid undershooting or overshooting.

19. Maintain scan pattern: rotor RPM, airspeed, landing area position, altitude, outside clearing, repeat.

20. Make simulated radio call when directed: “Phoenix Approach, Helicopter 123AB, simulated emergency, autorotating 10 miles north of Deer Valley Airport, practice autorotation for training.”

21. At instructor’s command (“Recover with power now”), execute smooth power recovery: Roll throttle on, coordinate collective increase as power arrives, apply right pedal to counteract torque, adjust cyclic to maintain heading and return to level flight attitude.

22. Monitor rotor RPM throughout recovery to ensure it remains within limits—not too low (insufficient power) or too high (overspeed risk).

23. Accept instructor feedback non-defensively and implement corrections on subsequent attempts.

24. Verbalize observations and concerns during ground break: “I noticed my descent rate increased when I made that right turn—was my bank angle too steep?”

25. Demonstrate progressive improvement through lesson, incorporating instructor feedback on rotor RPM control, airspeed precision, landing area selection timing, and maneuvering efficiency.

26. Self-evaluate performance against ACS standards and identify specific areas needing improvement.

27. Participate in post-flight debriefing by accurately describing performance, acknowledging errors, and asking questions about unclear concepts.

28. Complete assigned reading before next lesson: Rotorcraft Flying Handbook Chapter 11, AC 61-140.

29. Review POH/RFM height-velocity diagram and consider implications for low-altitude autorotations.

30. Practice chair-flying autorotation procedures including memory items, landing area selection verbalization, and power recovery sequence.

Completion Standards

The lesson is complete when the student consistently demonstrates the knowledge, risk management, and skills required by FAA-S-ACS-16 Area of Operation VIII, Task B (CH.X.B), as evidenced by:

Knowledge:

• Explains the elements of powerplant failure at altitude including recognition cues, immediate actions, and transition to established autorotation with rotor RPM priority.

• Describes effects of weight (increased descent rate, higher rotor energy requirements), temperature (performance degradation in heat), and density altitude (faster descent, reduced flare effectiveness) on autorotation performance with specific examples.

• Explains main rotor RPM management including factors affecting Nr (collective, airspeed, maneuvering), consequences of low rotor RPM (inadequate energy for flare, risk of blade stall), and corrective actions (immediate collective lowering).

• Demonstrates understanding of energy management by describing three energy forms (potential/altitude, kinetic translational/airspeed, kinetic rotational/rotor RPM) and explaining conversion/preservation strategies throughout autorotation.

• Identifies causes of high descent rates (improper airspeed, excessive collective, high density altitude, heavy weight, steep maneuvering) and their effects (reduced time, aggressive flare required, increased hard landing risk).

• Explains effects of varying bank angles (shallow acceptable, steep increases descent rate), airspeeds (below optimal = increased descent, above optimal = increased descent but energy available), and rotor RPM variations on autorotation performance.

Risk Management:

• Identifies minimum entry altitude for training (1,500-2,000 AGL) and explains risks of low altitude entries (insufficient time for analysis, limited recovery options).

• Applies 5 S’s criteria (size, shape, surface, surroundings, suitability) to landing area selection, accounting for altitude, wind, terrain, and obstructions.

• Recognizes risks of abrupt flight control inputs and demonstrates smooth, coordinated technique throughout autorotation.

• Describes turbulence and wake turbulence hazards, identifying avoidance strategies and appropriate responses if encountered.

• Explains windshear recognition and response priorities (rotor RPM maintenance above all).

• Demonstrates awareness of low rotor RPM dangers, verbalizing immediate corrective action (lower collective) and consequences of failure to correct (blade stall, loss of control).

• Acknowledges possibility of actual powerplant failure during practice and describes appropriate response.

• Maintains clearing procedures and collision awareness throughout autorotation despite high workload.

• Explains power-off Vne limitation per POH/RFM and its significance.

• Demonstrates helicopter trimming technique to reduce workload.

• Recognizes distraction risks and applies task prioritization (aviate first: maintain rotor RPM and establish autorotation; then navigate: select landing area; then communicate: radio calls as time permits).

Skills:

Per ACS standards for Task CH.X.B:

• Establishes autorotation with immediate recognition (simulated), memory items executed within 2-3 seconds (collective lowered, heading maintained with pedal, autorotation airspeed established).

• Establishes and maintains power-off glide with helicopter trimmed and autorotation airspeed ±5 knots throughout descent (60 knots ±5 knots or POH-specified airspeed).

• Maintains main rotor RPM within normal limits (green arc, typically 90-110% Nr) throughout entire autorotation without exceeding or dropping below green arc.

• Selects suitable landing area by 1,500 AGL using stated criteria, considering altitude (adequate to reach), wind (favoring headwind approaches), terrain (firm, level, obstacle-free), and obstructions (clear approach paths).

• Maneuvers to avoid undershooting or overshooting selected landing area using shallow banks (generally ≤15°), early turn initiation, and continuous position assessment relative to intended landing spot.

• Makes radio calls as appropriate in content, format, and timing: identifies aircraft, declares emergency (practice), provides location and intentions, requests assistance if applicable.

• Terminates approach with power recovery at safe altitude as directed by evaluator (typically 500-1,500 AGL for training) with smooth coordination: throttle application, collective increase timed to power availability, pedal coordination to maintain heading, and return to level cruise flight without rotor RPM exceedance or unusual attitudes.

Instructor Evaluation Criteria:

Student meets completion standards when instructor observes three consecutive autorotations demonstrating:

• Airspeed 60 knots ±5 knots (55-65 KIAS range) maintained throughout descent
• Rotor RPM remains within green arc with no excursions into yellow or red
• Landing area selected by 1,500 AGL with verbalized justification meeting 5 S’s criteria
• Maneuvering accomplished with bank angles ≤20° and no overshoot/undershoot of intended landing area
• Power recovery initiated at evaluator-specified altitude with smooth control coordination and no rotor RPM limits exceeded
• Radio call includes minimum required information (aircraft ID, emergency nature/practice, location, intentions)
• Risk management consistently applied (clearing procedures, scan pattern maintained, task prioritization demonstrated)

Endorsement Readiness:

Student is ready for commercial checkride (following completion of all required commercial maneuvers) when autorotation performance consistently meets the standards above across multiple flight lessons, various atmospheric conditions, different altitudes and entry configurations, and under simulated checkride stress with minimal instructor intervention required.

Instructor will document lesson completion in student logbook and training record, noting areas of strength and any items requiring continued practice in subsequent lessons. If standards not met, specific deficiencies will be identified and remedial instruction scheduled before progressing to 180-degree or full-touchdown autorotations.