View Full Version : Asymmetric Propellor thrust in climb / P Factor

3rd Dec 2006, 23:43
Anyone know of a clear illustration (in a book/on the web) showing relative airflow, effective angle of attack and a precise explanation of P factor?

There seems to be some confusion in the sources I've looked at thus far between AoA and relative forward speed differential between down going and up going propellor blades. Then there are the additional effects of prop wash, gyroscopics and so on.

Appreciate some clarity.

4th Dec 2006, 05:56
I haven't got any good pictures that you might not already have seen (ATPL JAR OXFORD). But here's what I know...

The main gyroscopic effect of an engine failure are due to the following:
- the amount of drag the featherd propeller produces
- loss of prop wash on the wing from the dead engine
- Differential airspeed over the wings due to live engine prop wash compared to the dead engines lack of propwash (full power on the live engine)
- turning moment from the live propeller (downgoing blade produces more thrust than up-going blade).

With a multi-engined aircraft p-factor isn't much of a factor to count in, since the thing that causes p-factor is the turning stream around the aircraft, produced by the propeller which hits the fin. And since the fin is located at an off-set position to the propeller stream it's not touching the fin, at least not by much...

This guy explains it pretty good: http://www.qmfc.org/school/asym.htm

4th Dec 2006, 07:28
You could also try See How It Flies (http://www.av8n.com/how/#contents) by John S. Denker.