The deadliest crash was blamed on an aerodynamic condition called " vortex ring state " that happened during an unusually rapid descent.
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It is possible to power out of vortex ring state, but this requires having about twice the power it takes to hover.
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The calculation of the velocity and the velocity potential at a given point is encapsulated inside the class definition of the vortex rings.
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The too-rapid approach of the second Osprey produced a phenomenon known as " vortex ring state "-- essentially a stall, the investigators concluded.
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The cause was determined to be vortex ring state ( VRS ), a fundamental limitation on vertical descent which is common to helicopters.
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Vortex rings may also be formed in the wake of a solid object that falls or moves through a fluid at sufficient speed.
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In the meantime, more research, supplemented by flight testing, is needed to understand better the circumstances in which vortex ring state sets in.
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But they also concluded that little had been known about vortex ring state's effect on the Osprey because of a dearth of testing.
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The lawyers, citing Pentagon reports, also said that the flight simulators used to train Osprey pilots were not programmed to simulate vortex ring state.
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This condition, also known as " vortex ring state, " occurs when a helicopter settles into the wash produced by its own rotor system.
