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.
It depends on the type of plane. Small, one-engine propeller planes (reciprocating engines) fly at speeds of 80 to 200 mph (130 to 320 km/hr).Jet airliners at cruising altitude average around 500 to 600 mph (800 to 960 km/hr).Military turboprops cruise at 350 mph (560 km/hr) and jet fighters routine exceed the speed of sound (768 mph or 1235 km/hr at sea level).t depends on the type of plane. Small, one-engine propeller planes (reciprocating engines) fly at speeds of 80 to 200 mph (130 to 320 km/hr).