Figure 8-1: Ground Effect
You may remember from ground school that the helicopter requires considerable power to hover. Therefore, it is important that you ensure that there is sufficient power available and that you monitor engine temperatures and pressure throughout all hovering manoeuvres.
The importance of lookout has been stressed in previous exercises. Lookout is extremely important when hovering. You will be flying near the ground so you must keep a sharp lookout to avoid accidentally flying into any obstacles.
A large, flat, open field, free of obstacles, should be selected for all hovering practice. Ensure that the surface is firm, and there is no loose material such as sand, snow, cut grass, or leaves, which the rotor wash may blow up and which might be ingested by the engine.
Light single-engine helicopters generally hover with the skids 3 to 5 feet above ground. This height will ensure that the skids are well clear of the ground and any low obstacles, and will also allow you to land safely should you ever have an engine failure. Take note that a normal hover at 3 to 5 feet will require less power than a hover at 10 feet.
EFFECTS OF CONTROLS
Hovering is defined as maintaining a constant height and heading over a given position on the ground. In a previous lesson you learned the effects of controls in cruise flight. These effects are very similar in the hover.
THE CYCLIC
In a hover, the cyclic is used to maintain a fixed position over a spot on the ground. As a recall, the cyclic controls disc attitude. A change of disc attitude will be followed by a change in fuselage attitude and, in hovering flight; this will cause the helicopter to move horizontally across the ground. For example, moving the cyclic forward or aft will cause the nose to drop or rise and the helicopter will move forward or backward. Similarly, moving the control to the left or right will cause the helicopter to move over the ground to the left or right.
In most types of helicopters there is a slight time lag between cyclic movement and aircraft response.
To cease horizontal motion and to regain a steady hover requires two cyclic movements; one to stop the movement, and a second to stabilize the helicopter in the hovering attitude. For example, if you note the helicopter is moving rearward the following cyclic movements will be required; the cyclic would be moved very slightly forward to stop the rearward movement, and then centralized in a position that maintains the helicopter in a steady hover.
The cyclic in the hover is more sensitive than in forward flight. A very small cyclic control movement will result in a very large helicopter movement. Your instructor will demonstrate this sensitivity of the cyclic in hovering flight.
North American helicopters usually hover with a left skid low attitude. This is caused by Tail Rotor Roll, which will be reviewed by your instructor (Fig 8-2).
Figure 8-2: Tail Rotor Roll
THE COLLECTIVE
In the hover the collective is used in the same manner as in forward flight. The collective controls the height of the hovering helicopter above the ground. Raising the collective will result in an increase in helicopter hover height and a decrease in hover height will result if the collective is lowered.
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