Vx, Vy, Best Glide for O-360/Hartzell

czechsix · #1 04-24-2006, 07:46 PM

Guys,

I'm getting ready to do performance testing for Vx, Vy, and best glide speeds in my RV-8A with O-360/Hartzell setup. I know there are some POH's floating around out there with these numbers in them but I'm curious how many people have measured this data carefully themselves? In particular to get good glide data one would have to pull the mixture and ideally test with the prop stopped, prop rotating with oil pressure & lever aft, and prop rotating without oil pressure (fine pitch). This could take quite a few engine-off glide tests and the numbers should be pretty close from one RV to the next...

Which brings me to my point: if there's any "consensus" on these speeds amongst those of you who've taken good data it would be nice to have those numbers as a starting point for my testing. For example if Vy is typically 80-90 kts I would narrow the range of my test from 75 to 95 instead of a much broader span of numbers.

It would be cool if someone made a spreadsheet collecting this kind of data from different airplanes. Checkoway are you listening?

Thanks,

--Mark Navratil
Cedar Rapids, Iowa
RV-8A N2D flying 29.2 hours now...

Ironflight · #2 04-24-2006, 09:14 PM

Mark,

When I was running these tests last fall in my -8 , I found that the drag/power curve was incredibly flat between 90 and 110 knots. I got just about the same ROC anywhere in there, and that made it very difficult to pin down the Best Rate speed. Even using the EFIS to record data, it was tough to keep the speed within a knot for long enough to get a stable rate - you're climbing 1500 fpm, and basically, the tolerance to which you can hold a speed emvelopes the changes in that speed range. (Sounds like gobbledy-gook, I know...)

Bottom line - I climb between 100-110 knots and get great performance. Best Angle? It really doesn't matter, becasue the performance is so stunning, that unless your runway is less than 100' long, you can just climb out at best rate.

You are correct that finding the best glide precisely is will be problematic.

Paul