Helicopter Flight Information
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Helicopter Flight Information |
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The H/V CurveThe H/V curve is the height/velocity diagram depicted in the helicopter operators handbook. These diagrams consists of both a high and low altitude portion. The low altitude portion depicts the area where a tail strike would likely result during the termination or deceleration of an autorotation, and the high altitude portion depicts the area where it would be difficult to complete an autorotation without serious damage due to the fact that the pilot may be unable to achieve sufficient airspeed to satisfactorily flare for a reduction in the sink rate, and ultimately for sufficient rotor energy to cushion the landing. The Height Velocity Diagram is developed specific to each make and model helicopter. This is accomplished by a highly skilled factory test pilot and a highly skilled FAA test pilot. The purpose is to determine the airspeeds and altitudes where the average pilot can safely execute an autorotation in the event of a power failure. It in no way implies a fatality rule as is implied when the H/V curve is inappropriately referred to as 'the dead mans curve'. The deeper the helicopter is operated within the height velocity curve, the more skill it takes to accomplish a safe autorotation should it become necessary. At some point the helicopter will likely be destroyed and a fatality could result. Operations within the height velocity diagram when required are considered acceptable risks, and an attempt is made to minimize these risks by thorough pre-flights and excellent maintenance programs. The helicopter passes through the height velocity curve on every approach and during many other commercial flight operations. During many commercial operations the entire duration of the flight is conducted very deep in the curve. In the simplest explanation, the H/V curve is a diagram where the shaded areas should should be avoided when possible as the average pilot may be unable to complete an autorotation without damage. The H/V curve sometimes (but not always) contains a take-off profile. Excepting the H/V curve is the risk helicopter pilots take for the joy of flying a machine with such great capabilities. It is an operational factor of helicopter aviation. |
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