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.
How fast does a helicopter go? A: In 2013, a test of the X3 helicopter set a record for helicopter speed at 255 knots, or about 293 miles per hour, according to Wired magazine. However, the average non-military helicopter cruises at a speed of about 130 to 145 miles per hour, claims Air Business International.