On Wed, 26 Oct 2005 03:14:11 GMT, "Marc J. Zeitlin"
wrote:

Jon Kraus wrote:

So what you are saying is that a windmilling engine is going to
produce enough vacuum to run the gyros? I think not...

Since the vacuum pump on most of our engines (an O-360 in my plane -
something similar in your Mooney) are run by a gear on the engine, as
long as the engine is spinning, the pump will be spinning. When I do my
runup, I get 5" of vacuum at anything over 1500 RPM or so - certainly at
1700 RPM or above.

So, as long as my engine windmills at more than 1500 RPM, I'll have more
than enough vacuum to run my gyros. And it does - I've tried it.

Try it yourself if you think not.....


You think wrong, Jon. Even at idle, most vacuum pumps produce enough
differential to keep rotors spinning satisfactorily.