The maximum forward speed of an average helicopter is limited to about 250 mph (402 km/h). Any faster, it is speeding beyond its limits.
If the blades rotate so fast that the tips go supersonic, it would result in the helicopter becoming uncontrollable. This is thanks to what is known as “Dissymmetry Of Lift” (also known as “retreating blade stall”), which is when there is an uneven amount of lift on opposite sides of the rotor disc.
If the blades rotate so fast that the tips go supersonic, it would result in the helicopter becoming uncontrollable. This is thanks to what is known as “Dissymmetry Of Lift” (also known as “retreating blade stall”), which is when there is an uneven amount of lift on opposite sides of the rotor disc.
Turbine-engined helicopters can reach around 25,000 feet. But the maximum height at which a helicopter can hover is much lower - a high performance helicopter like the Agusta A109E can hover at 10,400 feet. When the helicopter surpasses its maximum operating envelope, the helicopter becomes incredibly unstable. It is likely to pitch upward and roll to the left. The blades may also stall, causing the helicopter to become powerless.
According to the National Transportation Safety Board (NTSB), helicopters crash at a higher rate than airplanes. The crash rate for general aircraft is 7.28 crashes per 100,000 hours of flight time. For helicopters, that number is 9.84 per 100,000 hours
