A Maximum Performance Takeoff is used to climb at a steep angle to clear barriers in the flight path. It can be used when taking off from small areas surrounded by high obstacles. Before attempting a maximum performance takeoff, you must know thoroughly the capabilities and limitations of your equipment. You must also consider the wind velocity, temperature, altitude, gross weight, center-of-gravity location, adnn othe factors affecting your technique and the perfromance of the helicopter.
To safely accomplish this type of takeoff, there must be enough power to hover, in order to prevent the helicopter from sinking back to the surface after becoming airborne. This Hover Power Check can be used to determine if there is sufficient power available to accomplish this maneuver.
The angle of climb for a maximum performance takeoff depends on existing conditions. The more critical the conditions, such as high density altitudes, calm winds, and high gross weights, the shallower the angle og climb. In light or no wind conditions, it might be necessary to operate in the hazardous areas of the helicopter's height-velocity diagram during the beginning of the maneuver. Therefore, be aware of the calculated risk when operating in these areas. An engine failure at a low altitude and airspeed could place the helicopter in a dangerous position, requiring a high degree of skill in making a safe autorotative landing.
Technique
Before attempting a maximum performance takeoff, bring the helicopter to ahover, and determine the excess power available by noting the difference between the power available and that required to hover. For Piston powered helicopters, a Magneto check prior to this maneuver is advised as well prior to the hover check. You should also perform a balance and flight control check and note the position of the cyclic. Then position the helicopter into the wind and return the helicopter to the surface. normally, this maneuver is initiated from the surface. After checking the area for obstacles and other aircraft, select reference points along the takeoff path to maintain ground track. You should also consider alternate routes in case you are not able to complete the maneuver.
Begin the takeoff by getting the helicopter light on the skids (Position 1). Pause and neutralize all aircraft movement. Slowly increase the collective and position the cyclic so as to break ground in a 40 knot attitude. This is approximately the same attitude as when the helicopter is light on the skids. continue to slowly raise the collective until the maximum power available is reached. This large collective movement requires a substantial increase in pedal pressure to maintain heading (Position 2). Use the cyclic, as necessary, to control movement toward the desired flight path and, therefore, climb angle during the maneuver (Position 3). Maintain rotor RPM at its maximum, and do not allow it to decrease since you would probably have to lower collective to regain it. Maintain these inputs until the helicopter clears the obstacle, or until reaching 50 feet AGL fro demonstration purposes (Position 4). Then, establish a normal climb attitude and reduce power (Position 5). As in many maximum perfromance maneuver, the techniques you use affect the actual results. Smooth, coordinated inputs coupled with precise control allow the helicopter to attain maximum performance.
Common Errors
Failure to consider performance data, including the height/velocity diagram.
Nose too low initially, causing horizontal flight rather than more vertical flight.
Failure to maintain maximum permissable rotor RPM.
Abrupt control movements.
Failure to resume normal climb power and airspeed after clearing the obstacle.
Failure to consider performance data, including the height/velocity diagram.
