A maximum performance takeoff is used to climb at a steep angle to clear barriers in the departure flight path. To perform this maneuver successfully a pilot must consider the wind velocity, temperature, altitude, gross weight, center-of-gravity location, and other factors affecting performance of the helicopter.
The textbook procedure is this: After performing a hover power check to determine if there is sufficient power available, position the helicopter into the wind and begin by getting the helicopter light on the skids. Pause to neutralize all aircraft movement. Slowly increase the collective and position the cyclic to break ground in a 40-knot attitude. This is normally about the same attitude as when the helicopter is light on the skids. Continue to slowly increase the collective until the maximum power available is reached. Keep in mind this large collective movement requires a substantial increase in pedal movement to maintain heading. Use the cyclic, as necessary, to control movement toward the desired flight path and, therefore, climb angle during the maneuver. Maintain rotor rpm at its maximum, and do not allow it to decrease since you would probably have to lower the collective to regain it. Maintain these inputs until the helicopter clears the obstacle then establish a normal climb attitude and reduce power. As in any maximum performance maneuver, the techniques you use affect the actual results. Smooth, coordinated inputs coupled with precise control allow the helicopter to attain its maximum performance. Also, the helicopter will most likely be inside the shaded area of the height-velocity diagram where there is very little energy available to perform an autorotation in the event of an engine failure. Using maximum power would decrease the time the helicopter is exposed to a low energy situation.
However, other pilots I have talked to prefer a slightly different technique. Instead of using maximum power available, use the minimum power necessary to safely climb and clear the obstacle. The theory being that in the event of an engine failure the less power the pilot is using the more rotor rpm will be recoverable to help in the autorotation. Also, demanding high power might increase the probability of a part failure at a critical time. I would be interested in hearing comments on the two theories.
Tags: Tim McAdams