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The FAA states "The height–velocity diagram or H/V curve is a graph charting the safe/unsafe flight profiles relevant to a specific helicopter. As operation outside the safe area of the chart can be fatal in the event of a power or transmission failure it is sometimes referred to as the dead man's curve ."
In aerodynamics, the flight envelope, service envelope, or performance envelope of an aircraft or spacecraft refers to the capabilities of a design in terms of airspeed and load factor or atmospheric density, often simplified to altitude. [1] [2] The term is somewhat loosely applied, and can also refer to other measurements such as maneuverability.
The charts show the added lift benefit produced by ground effect. [ 3 ] For fan and jet-powered vertical take-off and landing (VTOL) aircraft, ground effect when hovering can cause suckdown and fountain lift on the airframe and loss in hovering thrust if the engine sucks in its own exhaust gas, which is known as hot gas ingestion (HGI).
Its comprises helicopter aerodynamics, stability, control, structural dynamics, vibration, and aeroelastic and aeromechanical stability. [1] By studying the forces in helicopter flight, improved helicopter designs can be made, though due to the scale and speed of the dynamics, physical testing is non-trivial and expensive.
Proper maintenance of the helicopter's damping system components can prevent ground resonance from taking hold. When it does occur, recovery is often possible if action is taken quickly. If sufficient rotor RPM exists, immediate takeoff can restore rotor balance by allowing the airframe to move and help dampen the oscillation freely. [ 1 ]
Dissymmetry of lift in an American-style helicopter. Consider a single-rotor helicopter in still air. For a stationary (hovering) helicopter, whose blades of length of r metres are rotating at ω radians per second, the blade tip is moving at a speed rω meters per second. As the blades rotate, the speed of the blade-tips relative to the air ...
Disk loading of a hovering helicopter is the ratio of its weight to the total main rotor disk area. It is determined by dividing the total helicopter weight by the rotor disk area, which is the area swept by the blades of a rotor.
The subsequent Model 205A-1 is equivalent to the UH-1H, which, compared to the 204, is longer, larger, and has better performance and a more powerful engine. [ 1 ] Over 60 civil Model 204B helicopters had been delivered by 1967, while further examples were built by Agusta-Bell until 1973. 12,000 Model 205s (including civil 205A-1s) were built ...