Straight and Level Flight is flight in which a constant altitude and heading are maintained. The attitude of the helicopter determines the airspeed and is controlled by the cyclic. Altitude is primarily controlled by use of the collective.

Technique

To maintain forward flight, the rotor tip-path plane must be tilted forward to obtain the necessary horizontal thrust componant from the main rotor.

This generally results in a nose-low attitude. The lower the nose, the greater the power required to maintain altitude, and the higher resulting airspeed.

Conversely, the greater the power used, the lower the nose must be to maintain altitude. Please refer to Figure 9-11.

When in straight and level flight, any increase in the collective, while holding airspeed constant, causes the helicopter to climb. a decrease in collective, while again holding airspeed constant, will cause the helicopter to descend. A change in the collective requires a coordinated change of throttle to maintain constant rotor RPM (unless governor equipped, in which that is done for you). Additionally, the antitorque pedals need to be adjusted to maintain heading and to keep the helicopter in longitudinal trim.

To increase airspeed in straight and level flight, apply forward pressure on the cyclic and raise the collective as necessary to maintain altitude. to decrease airspeed, apply rearward pressure on the cyclic adn lower the collective, as necessary to maintain altitude.

Although the cyclic is sensitive, there is a slight delay in control reaction, and it will be necessary to anticipate actual movement of the helicopter. when making cyclic inputs to control the altitude or airspeed of a helicopter, take care not to overcontrol. If the nose of the helicopter rises above the level flight attitude, apply forward cyclic pressure to bring the nose down. If this correction is held too long, the nose will drop too low. Since the helicopter continues to change attitude momentarily after the controls reach neutral, return the cyclic to neutral slightly before the desired attitude is reached. This principal holds true for any cyclic input.

Since helicopters are inherantly unstable aircraft, if a wind gust or turbulence causes the nose to drop, the nose tends to continue to drop instead of returning to a straight and level attitude as would a fixed-wing aircraft. Therefore you must remain alert and FLY the helicopter at all times.

Common Errors

Failure to properly trim the helicopter (if equipped), tending to hold antitorque pedal pressure and opposite cyclic. This is commonly called cross-coupling.
Failure to maintain desired airspeed.
Failure to hold proper control position to maintain desired ground track.

All helicopters have different visual clues that can assist you in maintaining a level flight attitude (such as using part of the canopy/instrument panel/compass against the horizon, etc.), if not, you can always reference the tip-path plane with respect to the horizon.


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Page Last Updated on: May-29-2002