Originally Posted by
Cubdriver
I was watching an aviation video where the pilot figured out his descent angle in order to make a fix and tell his autopilot what angle to use. Most people just use a descent rate in feet per minute. I never read of any easy way to do an angle calculation without a calculator, but this guy did it on his kneeboard real quick, and it was supposedly a real enactment, so I thought about it a little while, and came up with this fairly simple formula. Easy enough but still requires pen and paper.
>Divide the altitude to be lost by the distance in ft, and then divide by 1.7, and slide the decimal.
Ex. 5000 ft / 10 miles (61000 ft) = .082 / (1.7) = .0487° --> 4.8°
Anybody know one that does not require pen and paper?
It is a whole lot easier to use the 60:1 rule to calculate your flight path angle. Just get rid of the last 2 zeros in your altitude and you end up with 50/10= 5 degrees.
I never bother calculating my flight path angle. What is important to me is the descent rate required to meet the restriction. If i have to descend 5000ft in 10 miles at 200kts, my descent rate is 1667ft/min. That same crossing restriction at 400kts is 3333ft/min. Both of these are a 5 degree flight path angle, but there is a significant difference in the descent rate required.