myersf(at)comcast.net
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 Posted: Wed Jun 29, 2011 6:22 am Post subject: Yak-List: Things |
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I want chime in here a bit although not too much. As a lurker I hate to bring this up but...
It has always been my understanding that constant speed props are different whether on singles vs twins. I was taught that and I taught it that way.
When oil pressure goes to zero, singles go to flat, twins go to course. Heck, I had to create a lesson plan for it on my CFI-ME or MEI.
Turboprops are different again. Autocoursen, auto feather, garret type engine vs Pratt...
Now I have been corrected by other pilots about OWT I have perpetuated but I am pretty confident on this issue.
I don't know Mr Sapp but I think he had an experimental 4 blade prop on his plane. If the prop went to flat pitch when the engine failed, drag probably really increased even more than if he had the standard fixed found on a super cub.
On the other hand I wouldn't at all be surprised to hear that this prop was created to go course on failure or that Mr Sapp pulled the prop to full course to get more glide. Either way I think it was a great demonstration of airmanship.
That plane must have had a lot of power to need a 4 blade prop....
Fran
Sent from my Verizon Wireless 4GLTE smartphone
----- Reply message -----
From: "Bill Geipel" <czech6(at)mesanetworks.net>
To: "yak-list(at)matronics.com" <yak-list(at)matronics.com>
Subject: Yak-List: Things
Date: Wed, Jun 29, 2011 8:48 am
And u shut the mags off on your yak? I would advise against it. But u r a grown up.
It depends on the airplane to be sure. It was never mentioned. I am sure that some twins won't windmill at lift off speed.Got the T shirt. I am also sure that when the engine seizes it won't windmill, and I am equally sure that at that speed and altitude, u may not have a chance to feather it. Sure, once u reach 400' u have options. But the engine may not have read the same game plan as u. Many light twins need to be windmilling to feather.
..
Bill
On Jun 27, 2011, at 11:15 PM, Brian Lloyd <brian(at)lloyd..com (brian(at)lloyd.com)> wrote:
[quote]
On Mon, Jun 27, 2011 at 6:20 PM, Bill Geipel <[url=mailto:czech6(at)mesanetworks.net]czech6(at)mesanetworks.net (czech6(at)mesanetworks.net)[/url]> wrote:
| Quote: | What does caging the dead engine mean? If it's dead, you have lost the ability to Feather it haven't you?
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No. A dead engine that is producing zero power is still providing a load on the windmilling propeller. If it is windmilling, you can feather it. If it is NOT turning you can't feather it but then, if it is not windmilling, it is producing much less drag anyway. A stalled airfoil is producing much less drag than an airfoil that is producing lift near the critical AoA.
| Quote: | Doubtful that is windmilling at takeoff speed.
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Oh yes, it will windmill at takeoff speed! Try it in your Yak or CJ. Slow down to take-off speed and pull the throttle to idle. I betcha the prop keeps turning. If you aren't sure, turn the mags off for a couple of seconds. I promise you that the prop won't stop.
--
Brian Lloyd, WB6RQN/J79BPL
3191 Western Dr.
Cameron Park, CA 95682
[url=mailto:brian(at)lloyd.com]brian(at)lloyd.com (brian(at)lloyd.com)[/url]
+1.767.617.1365 (Dominica)
+1.916.877.5067 (USA)
[b]
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