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.
Because of their lower weight compared to engine power, some private jets travel faster than large passenger jet planes. 500 to 700mph It depends on the airplane. A Piper Archer will do about 135mph, a King Air will do around 300, an airliner like a 757 will go about 600, jet fighters will go about 1200 for real short distances and an SR-71 will go about 1800.