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.
Guinness World Records recognized NASA's X-43A scramjet with a new world speed record for a jet-powered aircraft - Mach 9.6, or nearly 7,000 mph. Answer The fastest speed wasâ¦ recorded by an unmanned aircraft called X-43. It can reach the speed of almost 7460 miles per hour. The fastest manned aircraft is X-15. Its top speed is 5115 miles per hour. This is very, very fast. Different ways of flight propulsion must have different categories as fastest in their method of power, to allow for this question to be answered properly. However, the overall fastest flight reached is Mach 9.8, which is about 12,144 km/h.