Autorotation Decision after a Sudden Loss of Engine Power over a Town
You are at 1,200 ft above ground level over a town, flying a light single-engine helicopter at 60 KIAS on a positioning flight with one passenger. Without warning the engine loses power; the low rotor RPM horn sounds and the rotor RPM begins to decay. Below you is a mix of two-storey buildings, a main road with traffic, and a park about 300 m ahead and slightly to the right. The wind is 10 kt from the left. You have practised autorotations but never in this environment. The passenger is shouting. The helicopter has a skid landing gear and no floats.
1. State the immediate actions in order and explain the energy management behind them.
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Immediate actions: lower the collective pitch fully and firmly to preserve rotor RPM, simultaneously apply right pedal to counter yaw, and establish the aircraft in a steady autorotative glide at the recommended speed. The collective lowering is the critical action because rotor RPM is the stored energy that gives you control and a flare; if RPM decays below the safe range, control is lost and recovery is impossible. Once established, select a landing area, turn into wind if height allows, and transmit a mayday. Energy management: the helicopter has potential energy from height and kinetic energy from airspeed. Lowering collective converts the descent into rotor RPM rather than into a decaying rotor. Airspeed is traded for a flare at the bottom, and height is traded for time to choose and align with a landing area. At 1,200 ft you have roughly a minute of glide, which is enough to select the park but not enough for indecision.
2. Compare the park, the main road and the rooftops as landing areas, and justify your choice.
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The park is the best option: it is open, likely free of people at short notice, and large enough to land with a modest run-on. It is 300 m ahead and slightly right, which is within gliding range from 1,200 ft at 60 KIAS. The main road is a poor choice: traffic, wires, street furniture and pedestrians make it hazardous, and a forced landing there risks collision with vehicles. Rooftops are the worst option: skid gear cannot absorb a rooftop landing, roofs may collapse, and there is no run-on space. The wind from the left means a turn into wind costs height and time; if the park is reachable without a large turn, take it and accept a slight tailwind or crosswind component rather than manoeuvre at low height. The judgement is to commit early to the best available area rather than to keep searching for a perfect one.
3. What would you say to the passenger, and what would you do in the last 100 ft?
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Brief the passenger in a firm, calm voice: 'We have an engine problem. I am landing in the park ahead. Sit back, hold your harness, do not touch the controls, and brace.' A short, specific instruction reduces panic and keeps the passenger from interfering. In the last 100 ft, maintain the recommended autorotation speed until the flare, then flare to convert airspeed into a reduced rate of descent, level the skids, and cushion the touchdown with collective as rotor RPM allows. Keep the landing into wind if the alignment permits, and be ready to run on if the surface is uneven. After touchdown, shut down, evacuate the passenger away from the rotor disc, and only then make a full mayday or urgency call with position and injuries. The priority order is: control the aircraft, protect the occupants, then communicate.