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kboatright1(at)comcast.ne
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 Posted: Tue May 01, 2007 6:21 pm Post subject: Power Off Glide |
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Today was a great flying day here in Georgia, so I made a tour of North Georgia after work. One of the things I experimented with today was the power off (prop stopped) glide characteristics of my plane.
After climbing to 9,500' I gradually eased the throttle back and let the engine cool to below 250F on the hottest cylinder. It didn't seem to want to get any cooler, even in what was more or less an idling glide, so I pulled the mixture to kill the engine. The prop continued windmilling down to under 70 knots indicated and then stopped. An unusual sight, to say the least, and not one I hope to see unexpectedly.
Next, I pulled out my little video camera and began to film instrument readings with the prop visibly stopped in the background.
As it turned out, the airplane's lowest sink speed was 80 knots indicated, which gave a sink rate of 700 to 750 fpm. I logged about 5 minutes of glider time, filming all the while, and then pushed the mixture back to rich, pushed the nose down and waited for the prop to begin windmilling as the airplane accelerated.
At about 120 knots, the prop made a half rotation and stopped on the compression stroke. This happened again a couple more times as airspeed increased, then, at 140 knots indicated, the prop began to windmill and the engine came back to life.
So, I gradually eased power up, flew back to my home field, and went to review the data from my camera.
Which hadn't filmed a darned thing. User error, I assume. My guess is that I hit the "record" button too soon after powering up the camera and it wasn't quite ready to make movies yet.
Some other day, maybe...
Kyle Boatright
160 HP, fixed pitch, RV-6
[quote][b]
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khorton01(at)rogers.com
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| Posted: Wed May 02, 2007 1:43 am Post subject: Power Off Glide |
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On 1 May 2007, at 22:19, Kyle Boatright wrote:
| Quote: | Today was a great flying day here in Georgia, so I made a tour of
North Georgia after work. One of the things I experimented with
today was the power off (prop stopped) glide characteristics of my
plane.
After climbing to 9,500' I gradually eased the throttle back and
let the engine cool to below 250F on the hottest cylinder. It
didn't seem to want to get any cooler, even in what was more or
less an idling glide, so I pulled the mixture to kill the engine.
The prop continued windmilling down to under 70 knots indicated and
then stopped. An unusual sight, to say the least, and not one I
hope to see unexpectedly.
Next, I pulled out my little video camera and began to film
instrument readings with the prop visibly stopped in the background.
As it turned out, the airplane's lowest sink speed was 80 knots
indicated, which gave a sink rate of 700 to 750 fpm. I logged about
5 minutes of glider time, filming all the while, and then pushed
the mixture back to rich, pushed the nose down and waited for the
prop to begin windmilling as the airplane accelerated.
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How does the lowest sink speed and sink rate compare to what you
would see with engine at idle? Many folks do this testing at idle,
and I'm wondering how much error that creates. It would also be
interesting to do the same test with engine OFF, but prop windmilling.
What type of prop do you have?
Kevin Horton
Ottawa, Canada
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kboatright1(at)comcast.ne
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| Posted: Wed May 02, 2007 2:58 am Post subject: Power Off Glide |
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