Helicopter Flight Information
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Helicopter Flight Information |
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Low Rotor RPMRotor RPM is directly controlled by the throttle when there is engine power available. When engine power is not available, the RPM is controlled by the collective through disk loading, and in some cases with the cyclic by disk G-loading. In the event of an engine failure, rotor RPM can only be controlled by the collective and/or the cyclic. The collective must be reduced to the point required to achieve rotor RPM within the acceptable range specified by the particular aircraft flight manual. If a condition exists where full down collective still will not provide satisfactory rotor RPM, it is possible to increase the RPM by increasing the G-load on the rotor disk by accomplishing S-turns, or a spiraling descent. If there is a loss of rotor RPM while engine power is available, the corrective action will be to lower the collective while simultaneously applying throttle as necessary to recover the RPM. In the event that full-throttle has been reached, then the only means of increasing rotor rpm will be through a reduction of collective pitch. In cases where the engine power has reached its maximum, it may become necessary to control the RPM with the collective even under powered flight. This technique is common at high altitude when the engine has reached maximum power output (full throttle). If a loss of rotor RPM occurs while in a hover, the proper corrective action is simply to land the helicopter; terrain permitting. Never raise the collective to maintain hover height while trying to recover the rotor RPM in a hover (unless you are over a mine field, then you might try some creative thinking). It is possible when over rough terrain to relieve some aircraft load by touching down any portion of helicopter landing gear which will result in unloading to some degree. The recognition of a low RPM condition is best by noticing a change in the tone of the rotor and/or engine noise; and secondarily by any associated warning lights or horns. Avoidance requires close monitoring of the RPM so that it is maintained within the acceptable range at all times.
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