Loss of Tail Rotor
A helicopter applies torque to the main rotor to keep it spinning at the proper speed.
An equal and opposite torque is applied back to the helicopter.
The tail rotor counters this torque to prevent the helicopter from spinning.
It also facilitates yaw control of the aircraft.
Losing a tail rotor is one of the worst malfunctions a pilot can encounter, frequently resulting in death.
Depending on the flight condition, the helicopter typically begins to spin at a very high rate.
Once a helicopter is spinning, it’s almost impossible to effectively use the cyclic controls, hence pitch and roll may be sacrificed in addition to yaw control.
(The malfunction discussed herein is for a complete tail rotor loss.
Stuck pedals, loss of tail rotor effectiveness, and fixed tail rotor pitch/feathering have different causes, symptoms and procedures.)
The following events may cause a loss of tail rotor thrust.
- The tail of the helicopter, including the tail rotor, may be chopped off by the main rotor. This can occur in an extreme flapping event.
- The tail rotor may strike another aircraft or other object, destroying its blades.
- The drive shaft powering the tail rotor may snap due to extreme loads, long-term fatigue loads, manufacturing defects, or corrosion/degradation of the drive system.
The primary symptom of tail rotor loss is immediate yaw in the direction opposite to main rotor rotation.
For example, American main rotors spin counterclockwise (viewed from above), so the loss causes the helicopter to spin clockwise, nose to the right.
The loss of yaw control is typically accompanied by roll and nose down pitch.
Additionally, torque and power indicators will suddenly drop 2-25% as the tail rotor stops consuming power.
The precise amount is highly dependent on the flight condition and helicopter model.
To minimize spinning, engine power must be reduced.
This can be accomplished by dropping the collective and/or reducing throttle.
Once this is done an autorotation procedure should be initiated, but without the capability of turning.
At higher speeds it may be possible to apply a small amount of power while searching for a landing spot,
without without getting the aircraft into a spin.
As usual, the pilot should aim to land in a flat area with level attitude and groundspeed near 0.