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Helicopter Checkride Oral Questions: Autorotations
No helicopter oral ends without autorotation theory. The examiner isn't just asking whether you can perform one — the flight test proves that — they're asking whether you understand why the rotor keeps turning without an engine, what manages rotor RPM in the descent, and how weight, density altitude, airspeed and wind change the outcome. Applicants who can draw the blade-region diagram from memory rarely struggle here.
Ground your answers in the Helicopter Flying Handbook (FAA-H-8083-21) and your specific rotorcraft flight manual: entry procedure, recommended autorotation airspeed, and rotor RPM limits are aircraft-specific, and quoting your RFM numbers is exactly what the examiner wants to hear.
Why the rotor keeps turning: the three blade regions
In powered flight, air flows down through the rotor; in autorotation, the helicopter descends through air flowing up relative to the disc, and that upflow drives the rotor. Along each blade there are three regions: the driven region (outer ~30% — net drag, slows the rotor), the driving region (middle ~25–45% — total aerodynamic force tilts forward of the rotational plane, accelerating the rotor), and the stall region (inner ~25% — operating beyond the critical AOA, producing drag). Steady rotor RPM is the equilibrium where driving forces balance driven and stall losses.
Collective is your RPM control: raising collective increases pitch everywhere, enlarging the driven and stall regions and decaying RPM; lowering collective does the opposite. Aft cyclic loads the disc and increases upflow, raising RPM (that's why RPM builds in the flare); forward cyclic and low G unload it. The instant response to engine failure is therefore: down collective to preserve RPM — rotor RPM is stored energy you cannot buy back once it decays below limits.
Managing the profile: airspeed, RPM, and the flare
The autorotation has four phases: entry (collective down, RPM in the green, pitch to the RFM's autorotation airspeed, pedal trim), steady-state descent (airspeed and RPM stable — typical trainers descend around 1,500–2,000 fpm), flare (around the RFM-specified height: aft cyclic trades airspeed for reduced rate of descent and groundspeed while building RPM), and touchdown/power recovery (level the ship, cushion with remaining collective — pulling collective consumes rotor RPM, so it's a one-time purchase).
Know your variables: higher gross weight increases the upflow through the disc, generally giving higher rotor RPM and a higher rate of descent; high density altitude increases true airspeeds and descent rate and reduces the energy margin; headwind stretches your glide over the ground and reduces touchdown groundspeed (always turn into wind if altitude allows); airspeed above or below the recommended value steepens the descent — minimum rate-of-descent and maximum-glide airspeeds are different numbers in your RFM, and you should know both and when you'd choose each.
Practice questions with answers & rationales
Q1. The engine fails in cruise. What is your immediate, first action and why?
Answer: Lower the collective — immediately. Engine failure removes the torque driving the rotor, and at cruise pitch settings the rotor decays within seconds; below the RFM's minimum rotor RPM the blades may stall with no recovery possible. Lowering collective establishes the upflow that keeps the rotor driven. Then: pedal trim (anti-torque requirement changes), cyclic to autorotation airspeed, pick a spot, attempt restart/mayday if altitude allows — but RPM first, always.
Q2. Explain the driven, driving and stall regions of the blade in autorotation.
Answer: The driven region (outer span) operates at low AOA where total aerodynamic force tilts aft of the rotational axis — it produces lift but net drag, decelerating the rotor. The driving region (mid-span) sees an inflow angle that tilts total aerodynamic force forward of the axis of rotation, producing a pro-rotational force. The stall region (inner span) exceeds the critical AOA and just drags. RPM is stable when driving force equals the driven plus stall losses; collective and disc loading shift the size of these regions, which is how you control RPM.
Q3. Why does rotor RPM increase during the flare?
Answer: Aft cyclic tilts the disc aft and increases the AOA and the upward inflow through the rotor — effectively enlarging the driving region — so the rotor accelerates. That stored RPM is exactly what you'll spend in the cushion. It's also why an aggressive flare can overspeed the rotor: you must be ready to manage RPM with collective if it approaches the upper limit.
Q4. How does high gross weight change the autorotation?
Answer: Heavier means more upflow is required to support the descent, so rate of descent increases and rotor RPM tends to run higher (you may carry a little collective to keep it in the green — which slightly helps glide). Touchdown energy is higher, so the flare and cushion must be more precise. Lightweight ships have the opposite problem: low inertia rotors and lower RPM in the descent, with less stored energy at the bottom.
Q5. What's the difference between minimum rate-of-descent and maximum-glide airspeed, and when would you use each?
Answer: Minimum rate-of-descent airspeed (slower) maximizes your time aloft — use it when your landing spot is essentially below you and you want time, or to troubleshoot/transmit. Maximum-glide airspeed (faster) maximizes distance over the ground — use it to stretch to a better landing area. Both are in the RFM; wind modifies the choice (add into a headwind for distance). Quoting your aircraft's two numbers from memory is the expected standard.
Q6. Why is a downwind autorotation so much worse than into the wind?
Answer: Wind doesn't change anything aerodynamically in the air mass — but it changes groundspeed at touchdown and ground distance covered. Downwind, your touchdown groundspeed is wind speed higher, energy goes with velocity squared, and the flare must dissipate far more energy over more ground. Into wind, ground run can approach zero. That's why pattern altitude awareness of wind, and turning into wind during the entry if altitude allows, are briefed before every flight.
Q7. What does the freewheeling unit do, and how do you know it worked?
Answer: It's an overrunning (sprag) clutch between the engine and transmission that automatically disengages the engine when engine RPM drops below rotor RPM — letting the rotor turn freely in autorotation and also driving the tail rotor and accessories from rotor energy. Confirmation in flight: needles split (rotor needle stays up while engine needle drops). If it failed to disengage, the dead engine would drag the rotor down — the emergency would be unmanageable, which is why the unit is checked per the RFM/maintenance schedule.
Common mistakes to avoid
- Answering 'pick a landing spot' or 'make a radio call' as the first action. Collective down is the only acceptable first answer.
- Describing only two blade regions, or putting the driving region at the tip. Draw it: driven outboard, driving mid-span, stall at the root.
- Not knowing your RFM's autorotation airspeed, rotor RPM limits, or the difference between min-descent and max-glide speeds.
- Saying 'pull collective to slow the descent' early in the profile — collective spends RPM; it's only purchased once, at the cushion.
- Ignoring wind in the scenario answer. Examiners deliberately set up tailwind entries to see if you mention turning into wind.
- Treating low rotor RPM casually. Below the RFM minimum, rotor stall is unrecoverable — say it with the seriousness it deserves.