A Running Takeoff in a skid type helicopter or a rolling takeoff in awheeled helicopter is sometimes used when conditions of load and/or density altitude prevent a sustained hover at normal hovering altitude. However, you should not attempt this maneuver if you do not have sufficient power to hover, at least momentarily. If the helicopter cannot be hovered, its performance is unpredictable. If the helicopter cannot be raised off the surface at all, sufficient power might not be available to safely accomplish the maneuver. If you cannot momentarily hover the helicopter, you must wait for conditions to improve or off-load some of the weight.
To accomplish a safe running or rolling takeoff, the surface area must be of sufficient length and smoothness, and there cannot be any barriers in the flight path to interfere with a normal climb.
For wheeled helicopters, a Rolling Takeoff is sometimes used to minimize the downwash created during a takeoff from a hover.
Please refer to the Figure. To begin the maneuver, first align the helicopter to the takeoff path. Next, increase the throttle to obtain takeoff RPM, and increase the collective smoothly until the helicopter becomes light on the skids or landing gear (Position 1). Then, move the cyclic slightly forward of the neutral hovering position, and apply additional collective to start the forward movement (Position 2). to simulate a reduced power condition during practice, use one to two inches less manifold pressure, or three to five percent less torque, than that required to hover.
Maintain a straight ground track with lateral cyclic and heading with the antitorque pedals until a climb is established. As effective translational lift (ETL) is gained, thehelicopter becomes airborne in a fairly level attitude with little or no pitching (Position 3). Maintain an altitude to take advantage of ground effect, and allow the airspeed to increase toward normal climb speed. Then, follow a climb profile that takes you through the clear area of the particular helicopter's height velocity diagram (Position 4). During practice maneuvers, after you have climbed to an altitude of 50 feet, establich the normal climb power and attitude.
SHALLOW APPROACH AND RUNNING/ROLL-ON LANDINGS
Use a Shallow Approach and Running Landing when a high-density altitude or a high gross weight condition, or some combination thereof, is such that a normal or steep approach cannot be made because of insufficient power to hover. To comphensate for this lack of power, a shallow approach and running landing makes use of effective translational lift (ETL) until surface contact is made. If flying a wheeled helicopter, you can also use a roll-on landing to minimize the effect of downwash. The glide angle for a shallow approach is approximately 5 degrees. Since the helicopter will be sliding or rolling to a stop during this maneuver, the landing area must be smooth and long enough to accomplish this task.
A shallow approach is initiated in the same manner as the normal approach except that a shallower angle of descent is maintained. Please refer to the Figure below.
The power reduction to initiate the desired angle of descent is less than that for a normal approach since the angle of descent is less (Position 1). As you lower the collective, maintain heading with proper antitorque pedal pressure, adn RPM with the throttle. Maintain approach airspeed until the apparent rate of closure appears to be increasing. Then, begin to slow the helicopter with aft cyclic (Position 2).
As in normal and steep approaches, the primary control for the angle and rate of descent is the collective, while the cyclic primarily controls the groundspeed. However, there must be a coordination of all the controls for the maneuver to be accomplished successfully. The helicopter should arrive at the point of touchdown at or slightly above effective translational lift (ETL). Since translational lift diminishes rapidly at slow airspeeds, the deceleration must be smoothly coordinated, at the same time keeping enough lift to prevent the helicopter from settling abruptly.
Just prior to touchdown, place the helicopter in a level attitude with the cyclic, and maintain heading with the antitorque pedals. Use the cyclic to keep the heading and ground track identical (Position 3). Allow the helicopter to descend gently to the surface ina straight-and-level attitude, cushioning the landing with the collective. After surface contact, move the cyclic slightly forward to ensure clearance between the tailboom and the rotor disc. You should also use the cyclic to maintain the surface track (Position 4). You normally hold the collective stationary until the helicopter stops; however, if you want more braking action, you can lower the collective slightly. Keep in mind that due to the increased ground friction when you lower the collective, the helicopter's nose might pitch forward. Excercise caution not to correct this pitching movement with aft cyclic since this movement could result in the rotor making contact with the tailboom. During the landing, maintain normal RPM with the throttle and directional control with the antitorque pedals.
For wheeled helicopters, use the same technique except after landing, lower the collective, neutralize the controls, and apply the brakes, as necessary, to slow the helicopter. Do not us aft cyclic when bringing the helicopter to a stop.
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Page Last Updated on: Nov-06-2017