Risk factors. Factors that increase the risk of stuttering include: 1  Having relatives who stutter. 2  Stuttering tends to run in families. 3  Delayed childhood development. 4  Children who have developmental delays or other speech problems may be more likely to stutter. 5  Being male. 6  Males are much more likely to stutter than females are. 7  Stress.
The average speed for a four-seat helicopter is 130 to 145 miles per hour. Because smaller helicopters have smaller engines, the average speed for a two-seat is 90 to 105 mph. The fastest helicopter on Earth as of 2014, the X3 Eurocopter, can fly at 300 mph. Keep Learning.
Retarding blades do not suffer this problem as the airspeed at the tips is reduced, by virtue of the fact that the blades are travelling in the same direction as the airflow caused by flight. <br /> For example: Suppose the speed of Rotor Blade tip (helo in a hover) = 350mph. Speed of the Helicopter in flight = 150mph. Speed of Advancing Blade (in flight) = 350 + 150 = 500mph This simple calculation will determine the maximum speed of the helicopter. Most typical helicopters can only go about 150mph or maybe a little faster. Compound helicopters or the V-22 Tilt-Rotor can fly at over 200mph or even 300mph. The maximum airspeed of a helicopter is limited by the speed of the rotor blade.