Helicopter flight controls
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[edit] Flight regimes
Helicopters can operate in several flight regimes:
- Forward flight is when airspeed is greater than 15 mph, which is about the point of effective translational lift (ETL). At ETL, less engine power is required until about 40 mph airspeed when power requirements increase again.
- Hover in ground effect(IGE) is when the helicopter is flying within a half main rotor diameter above the ground and less than about 15 mph airspeed (ETL). This requires a significant amount of power, much more than in forward flight, but less then hover out of ground effect.
- Hover out of ground effect(OGE) occurs when the helicopter is hovered at a height greater than half the main rotor diameter. This requires the greatest amount of engine power.
The differing power requirements of a helicopter at different speeds is related to the three types of drag experienced. Induced Drag, Rotor Profile Drag and Parasite Drag.
- Autorotation is a descent with no engine power used. The engine can still be running, but a one-way freewheel disengages the engine from the transmission. Autorotation is used for emergency landing or high speed descent.
[edit] Mnemonics
The following mnemonics are used to recall changes necessary for speed-up and for slowing:
- Speed-Up: "L.L.F. Lift, Left, Forward" - Lift Collective, Left Pedal and Forward Cyclic.
- Slow-Down: "R.R.A. Reduce, Right, Aft" - Reduce (drop) Collective, Right Pedal and Aft Cyclic.
Note that left pedal is applied with increased collective for counterclockwise rotating main rotor (advancing from pilots right to left). This is common in most helicopters built in Italy, the UK, or the United States. For clockwise rotating main rotors (French, Russian, or Soviet designed helicopters), right pedal is applied with increased collective.
The following is a table of helicopter flight controls.
| Name | Directly controls | Primary effect | Secondary effect | Used in forward flight | Used in hover flight |
|---|---|---|---|---|---|
| Cyclic lateral | Varies main rotor blade pitch fore/aft | Tilts main rotor disk laterally via the swashplate | Increase descent rate | To turn the aircraft | To move sideways |
| Cyclic longitudinal | Varies main rotor blade pitch left/right | Tilts main rotor disk longitudinally via the swashplate | Increase descent rate | Control attitude | To move forwards/backwards |
| Collective | Collective angle of attack for the rotor main blades via the swashplate | Increase/decrease vertical thrust vector | Increase/decrease torque and engine RPM | To adjust vertical speed | To adjust skid height/vertical speed |
| Pedals | Collective pitch supplied to tail rotor blades | Yaw rate | Increase/decrease torque and engine RPM (less than collective) | Adjust sideslip angle | Control yaw rate/heading |
