In normal operations, use the Rapid Deceleration or Quick Stop maneuver to slow the helicopter rapidly and bring it to a stationary hover. The maneuver requires a high degree of coordination of all controls. It is practiced at an altitude that permits a safe clearance between the tail rotor and the surface throughout the maneuver, especially at the point where the pitch attitude is highest. The altitude at completion should be no higher than the maximum safe hovering altitude perscribed by that particular helicopter's manufacturer. In selecting an altitude at which to begin the maneuver, you should take into account the overall length of the helicopter and its height-velocity diagram. Even though the maneuver is called a rapid deceleration or quick stop, it is performed slowly an smoothly with the primary emphasis on coordination.

Technique

Please refer to the Figure below. During training always perform this maneuver into the wind (Position 1). After leveling off at an altitude of between 25 and 40 feet, depending upon the manufacturer's recommendations, accelerate to the desired entry speed, which is approximately 45 knots for most training helicopters (Position 2). The altitude you choose should be high enough to avoid danger to the tail rotor during the flare, but low enough to stay out of the hazardous areas of that helicopter's height-velocity diagram throughout the maneuver. In addition, this altitude should be low enough that you can bring the helicopter to a hover during the recovery.

At (Position 3), initiate the deceleration by applying aft cyclic to reduce forward groundspeed. Simultaneously, lower the collective, as necesssary, to counteract any climbing tendancy. The timing must be exact. If you apply too little down collective for the amount of aft cyclic applied, a climb results. If you apply too much down collective, a descent results. A rapid application of aft cyclic requires an equally rapid application of down collective. As collective pitch is lowered, apply proper antitorque pedal pressure to maintain heading, and adjust the throttle to maintain RPM.

After attaining the desired speed (Position 4), initiate the recovery by lowering the nose and allowing the helicopter to descend to a normal hovering altitude in level flight and zero groundspeed (Position 5). During the recovery, increase collective pitch, as necessary, to stop the helicopter at normal hovering altitude, adjust the throttle to maintain RPM, and apply proper antitorque pedal pressure, as necessary, to maintain heading.

Common Errors

Initiating the maneuver by applying down collective.
Initially applying aft cyclic stick too rapidly, causing the helicopter to ballon (climb).
Failing to effectively control the rate of deceleration to accomplish the desired results.
Allowing the helicopter to stop forward motion in a tail-low attitude.
Failing to maintain proper rotor RPM.
Waiting too long to apply collective pitch (power) during the recovery, resulting in excessive manifold pressure or an over-torque situation when collective pitch is applied rapidly.
Failing to maintain a safe clearance over the terrain.
Improper use of antitorque pedals resulting in erratic heading changes.

The most likely reason to perform a quick stop that is practiced is an aborted takeoff, or in which an obstacle has blocked your departure path. Remember that it is done slowly, and make all movements coordinated. But quick stops are fun maneuvers to do as well.


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Page Last Updated on: Nov-06-2017