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[1] [2] Unlike fixed-wing aircraft, of which the stall occurs at relatively low flight speed, the dynamic stall on a helicopter rotor emerges at high airspeeds or/and during manoeuvres with high load factors of helicopters, when the angle of attack(AOA) of blade elements varies intensively due to time-dependent blade flapping, cyclic pitch and ...
Retreating blade stall is a hazardous flight condition in helicopters and other rotary wing aircraft, where the retreating rotor blade has a lower relative blade speed, combined with an increased angle of attack, causing a stall and loss of lift. Retreating blade stall is the primary limiting factor of a helicopter's never exceed speed, V NE. [1]
The McDonnell XV-1 could slow its rotor from 410 to 180 RPM. The slowed rotor principle is used in the design of some helicopters.On a conventional helicopter the rotational speed of the rotor is constant; reducing it at lower flight speeds can reduce fuel consumption and enable the aircraft to fly more economically.
However, when the helicopter starts to move forward its speed is added to the speed of the blades as they advance towards the front of the aircraft, and subtracted as they retreat. For instance, if the helicopter is flying forward at 100 km/h, the advancing blades see 300 + 100 km/h = 400 km/h, and for the retreating ones its 300 – 100 km/h ...
This situation, when not immediately recognized can cause a severe loss of aircraft controllability. Retreating blade stall is a factor determining the maximum forward speed of the helicopter, the never-exceed speed (V NE). At very high forward speeds, the advancing blade may go supersonic. This is another factor determining the never-exceed speed.
The National Weather Service reported that wind gusts of up to 25 mph were possible in the area throughout the evening. The U.S. Army described the helicopter as a UH-60 Blackhawk based at Fort Belvoir in Virginia. A crew of three soldiers were onboard the helicopter, an Army official said. The helicopter was on a training flight.
A helicopter crash off the coast of Kauai, Hawaii on Thursday has left one person dead and two people missing, according to authorities.. The crash was reported around 1.20pm, a quarter of a mile ...
It has a maximum speed of 18 miles per hour (29 km/h). [2] The Ruppert Archaeopteryx has a certified stall speed of 30–39 kilometres per hour (19–24 mph). [3] The Vought XF5U can fly as slow as 32 kilometres per hour (20 mph). [4] The Tapanee Pegazair-100 stall speed is 45 kilometres per hour (28 mph).