wunder beta

📘 The quiet is not the danger

Imagine the helicopter crossing a field when the engine suddenly stops driving the rotor. The cabin may become startlingly quiet, but the aircraft is not immediately falling like a stone. A freewheeling unit, or overrunning clutch, disconne

4
lessons
~20 min
to learn
Adults
level
Start the course →

What you’ll learn

  1. The moment power disappearsExplain how a helicopter transitions from powered flight to autorotation after engine power is lost.The freewheeling unit, collective, and descending rotor establish the emergency's first aerodynamic exchange.
  2. The rotor becomes a windmillDescribe how upward airflow, airspeed, pedals, and rotor rpm interact during an autorotative descent.The rotor keeps turning through aerodynamic forces while the pilot balances speed, heading, and stored energy.
  3. Trading height for controlConnect autorotation to landing-site choice, the height-velocity envelope, and aircraft-specific procedures.Altitude is spent deliberately, and the safest energy state depends on the helicopter and its flight manual.
  4. The last few secondsExplain how the flare and final collective input reduce descent for touchdown while preserving control margins.The landing converts rotor energy into a controlled arrival, but the surface and starting energy still set the outcome.

Questions this course answers

What keeps the main rotor connected to useful airflow after engine power is lost?

In autorotation, the helicopter descends so air flows upward through the rotor and drives the blades aerodynamically.

What is the immediate purpose of lowering collective after an engine failure?

Lowering collective reduces lift and drag, starts the descent, and helps establish the upward airflow that sustains rotor rpm.

What does the height-velocity diagram warn about?

The diagram combines altitude and airspeed to show regions with reduced reaction time or insufficient energy for a successful autorotation.

What does the flare do near the ground?

The flare changes attitude and airspeed so stored rotor kinetic energy can help arrest the descent before touchdown.

Why must the final collective input be timed carefully?

Raising collective increases lift and drag, so using it too early can spend the rotor energy needed for the final landing.

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