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.
The F-15 speed is mach 2.5, the Mig 25 is mach 3.2. The Concorde could fly around mach 2, but it's not in use any more. its not the concord. The SR-71 black bird(mach 3 or about 2100mph)is the fastest military jet and the NASA X-43 scramjet(mach 9-10 or about 6300-7000mph) is the fastes unmanned jet. The fastest TRUE JET is the SR-71. The key word is true JET! thats even a bit of strech for the blackbird.