What occurs to a helicopter during cruise when the stick is moved forward without making other adjustments?
Refer to figure.
The three basic controls of helicopters are:
- Cyclic control;
- Collective control; and
- Tail rotor control.
Cyclic control is the primary control used to change the direction of flight in a helicopter typically located on the pilot's stick or joystick and it works in coordination with the collective control to change the helicopter's direction and altitude.
The cyclic control alters the pitch of the main rotor blades at different points around the rotor disk by tilting the swashplate assembly.
When a cyclic control input has been made, the rotor blade pitch will increase for one-half of a revolution and decrease for the next half and as a result, it alters the rotor disc attitude.
A change in the rotor disc attitude means that a horizontal component of the Total Rotor Thrust is generated. When cyclic control is applied to a direction, then the rotor disc tilts to the same direction and the horizontal component of the Total Rotor Thrust points to the same direction as well, providing the driving force for horizontal motion at the corresponding direction.
Specifically, when the stick is moved forward during cruise in a helicopter without making other corrections, the helicopter's
- speed increases and
- the sink rate increases.
This is because moving the stick forward causes the nose to pitch down, reducing the angle of attack, which increases forward speed and causes the helicopter to lose altitude more quickly.
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