RE: Calculate speed
Yeh , I use it quite often when a gun isn't around. Lets say your runway is 700ft long and your plane flys it in 6 seconds (roughly)
700 ft div by 6 seconds = 116 ft per second
116 x 60 x 60 = 417600
417600 div by 5280 = 79mph
The 60 60 thing is 60 seconds in a minute and 60 minutes in an hour and the 5280 is the mile.