John Hafen wrote:

What do you recommend as the “Glide Ratio” in the Chelton System User Programmed Settings?

John,

I’m using 20:1 and it seems just about right. In a couple of tests (from 10,000 and 17,000’) I was able to make a 180 and get to an airplane behind me with a bit of altitude to spare at the end. I think I could do a bit better from higher up. I considered going to 22:1, but decided against it because I was testing in a “known” situation/plan for this test and didn’t allow for reaction/analysis time (WTFO…to use and old Navy expression).

 

I’d also strongly suggest you set a value and test it yourself (carefully!), as the largest factor is the windmilling prop. My MT 4-blade will almost feather, maintaining about 700 RPM with the throttle at full idle, and giving me approx 600 FPM down at 120 KTS IAS. Even a small amount of additional RPM increased the descent rate dramatically; likewise, stopping the prop (if you can), will yield an even better glide ratio.

 

This later observation is from an actual engine failure in flight many years ago; I have not tried this with my Lancair. I had a camshaft drive gear failure in  Cherokee 235 at 13,500 near Winslow, AZ. I lifted the nose to try to stop the prop, and the very bad sounds coming from the engine compartment—I could hear the engine eating itself. Had to slow to very near stall to do this, but once I went back to best glide speed, was able to dead-stick into Winslow easily. Based on my earlier practice, I’d have bet there was no way to make the airport. After cleaning my pants and fixing the airplane, I actually tested this. Stopping the prop on that airplane added at least 50% to the glide range.

 

I’m not sure this last part can be related to Lancair operation at all—and I don’t intend to test/practice this maneuver in mine, but if I ever need to do it for real, I’ll likely try to stop the prop to pick up the extra range.

 

Hope this helps.

Bob P