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Clockwise Rotating Helicopter Differences

Clockwise Rotating Helicopter Differences

With some members learning in the Guimbal Cabri G2 helicopter and others owning the experimental Rotorway helicopter, we decided to add this lesson.

In this video, we discuss the differences you will experience with torque and gyroscopic precession, when flying a clockwise turning main rotor system.

In reality, adapting to the differences will come quite natural to a somewhat experienced pilot. It is more challenging to explain the differences, than it is to jump seats and fly the opposite rotating system.

Most training helicopters, until recently, have been counterclockwise systems. Example: Robinson, Enstrom, & Schweizer. 

The newest training helicopter and some experimental ones are clockwise systems.

Example: Guimbal Cabri and Rotorway.

Gyroscopic Precession

Note that gyroscopic precession will be opposite In Clockwise rotating helicopters.

For this reason, you will notice a difference in the following aerodynamics.

Transverse Flow Effect will cause the helicopter to drift left at approximately 10 knots, instead of right. 

This is due to the front of the rotor system becoming clean and this increased lift is felt 90 degrees later in the plane of rotation (right side). To avoid drift on take off, the pilot adds a little right cyclic at this point.

Another thing that the opposite rotation will affect is Retreating Blade Stall. The helicopter will pitch up and lean to the right (retreating side), due to the lack of lift occurring on the right side (retreating side), and the lack of lift is felt 90 degrees later (on the rear of the disk). Recovery is the same, lower collective some and slow down.

Torque

Second thing to consider is the torque. Torque and Anti-torque are opposite in a clockwise rotating helicopter.

For this reason, you will notice the following differences in aircraft characteristics.

The tail rotor will be on the right side, and thrusting to the left. The aircraft will want to spin left due to main rotor torque, and the tail rotor is countering that with thrust in the opposite direction. This makes the right pedal the “power or increased pitch pedal”.

Any loss of tail rotor function will cause the helicopter to yaw left. An engine or transmission failure will cause the helicopter to yaw right.

There are several things to talk about with this change. 

When you reach ETL on take off, you will need less right pedal to maintain heading.

So combine the difference in gyroscopic precession and torque, and you will note that the pilot will add some right cyclic as the helicopter hits 10 knots and left pedal at 16-24 knots in order to maintain track and heading during take off.

One example of a loss of tail rotor function would be total failure. Another is LTE (loss of tail rotor effectiveness). 

LTE (loss of tail rotor effectiveness)

Fast left pedal turns becomes the concern for (LTE). Two of the “dangerous winds” for LTE will be different in a clockwise rotating system.

The tailwind remains the same, although a front right quartering wind becomes dangerous due to main rotor disk interference. A right 90 degree crosswind becomes dangerous, due to the danger of tail rotor vortex ring state.

Translating Tendency

Translating tendency will be opposite in a clockwise rotating system. The clockwise system will drift left in a hover, due to the tail rotor thrusting in that direction. This is corrected by pilot input on the cyclic or rigging of the mast.

Low G

Low G characteristics in the clockwise rotating system will be slightly different due to tail rotor thrusting in the opposite direction. After feeling light in the seat due to a push over or turbulence, the helicopter will roll to the left due to tail rotor thrust. 

The recovery is the same! Gentle aft cyclic to reload the main rotor system, before correcting for the roll!