|
|
Let's say we have an airplane traveling at 200 Kts with a 6 foot diameter (D) prop operating at 2500 rpm.
An ordinary calculation would show the tip (per minute) to be Pi x D x rpm or
6 x Pi x 2500 = 47124 ft per min or 535 mph.
But, the tip is describing a helix because, at 200 Kts, the plane is moving forward at 1,215,223 feet per hour. The length of the helix path is:
Square Root ( (Pi x D)squared + distance squared)
(Pi x 6) squared = 355.1
distance of one revolution = 1215223 / 60 = 20253 / 2500 = 8.1 feet per revolution.
distance squared = 65.6
And the square root of the sum = SQRT (420.7) = 20.5 feet per revolution or
20.5 x 2500 = 51,250 feet per minute or
51250 x 60 = 3,075,000 feet per hour or 582 mph.
Aren't we getting close to Mach 1?
What about when we Race at 2700 rpm?
What about a IV or a Legacy?
Scott Krueger
Sky2high@aol.com
LNC2 N92EX IO320 Aurora, IL (KARR)
|
|