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Ernie
Joined: 11 Jan 2006
Posts: 513
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 Posted: Tue May 06, 2014 7:04 am Post subject: High Altitude Takeoff Mixture |
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I have been doing some flight planning in case I decide to purchase a CJ in the high country and came up with a question. Forgive my ignorance since I've only ever flown in the flatlands. Stock CJ's have a mixture tab which pulls the mixture lever back with the throttle. What would I do if I were in some airport with a density altitude of 12k ft? as would be common on a hot day any where in the mountain country?
Assuming the answer is push the mixture control with the throttle on takeoff, where would I stop pushing the mixture? half way? Personal experience has taught me that mixture control next to full throttle = mixture cutoff and no fuely no flyee.
Thanks
Ernie
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barryhancock
Joined: 09 Oct 2008
Posts: 285
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| Posted: Fri May 09, 2014 2:13 am Post subject: Re: High Altitude Takeoff Mixture |
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Ernie,
First of all, our home airport is at 5500' and I've never seen a 12,000'DA day. My experience is there is no need to worry about the mixture on a high and hot day with these engines. Of course, you can easily be over rich on taxi, but I've never experienced an engine wanting to quit do to flooding at full power. If you do feel the engine shuddering on take off, you are at full throttle and can easily adjust the mixture leaner to smooth things out, even if the plane still has the obnoxious tab on the mixture control.
Again, I've flown multiple stock CJ's on high DA days without any issues. Your climb performance, however, is gonna be less than stellar. Oh, and there's also these big things we call "rocks" that you need to worry about. 
Hope this helps.
Cheers,
Barry 
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Worldwide Warbirds, Inc.
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Pete Fowler
Joined: 07 Jul 2009
Posts: 76
Location: California
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| Posted: Fri May 09, 2014 8:14 am Post subject: Re: High Altitude Takeoff Mixture |
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Hi Ernie,
First of all the mixture stop should have been removed a long time ago. US fuel and long taxi times (if you're a formation pilot) with a stock Housai setup guarantee carboned-up and gunked up engines with the original mixture stop. You need to go nearly full lean on a stock Housai while taxiing for engine performance.
I've taken off from Big Bear on a 9,500ft DA day with my Housai and I found that it would lean surge if I did anything non-standard other than maybe one or two clicks forward. With a normal Housai setup, the full-rich is WAY rich and full lean is running but will surge.
Typical for me, takeoff with a Housai is not full-rich but for higher altitudes but only a little forward (lean) of full rich.
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Ernie
Joined: 11 Jan 2006
Posts: 513
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| Posted: Fri May 09, 2014 8:22 am Post subject: High Altitude Takeoff Mixture |
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On my old CJ, I had the tab and liked it. I never had carbon foul problems with mine, but again, I live at sea level. About 90% of my flying was done below 4000 ft and I rarely touched the mixture control. Flew it full rich all the time.
Ernie
On Fri, May 9, 2014 at 12:14 PM, Pete Fowler <pfdesign1(at)cox.net (pfdesign1(at)cox.net)> wrote:
[quote]--> Yak-List message posted by: "Pete Fowler" <pfdesign1(at)cox.net (pfdesign1(at)cox.net)>
Hi Ernie,
First of all the mixture stop should have been removed a long time ago. US fuel and long taxi times (if you're a formation pilot) with a stock Housai setup guarantee carboned-up and gunked up engines with the original mixture stop. You need to go nearly full lean on a stock Housai while taxiing for engine performance.
I've taken off from Big Bear on a 9,500ft DA day with my Housai and I found that it would lean surge if I did anything non-standard other than maybe one or two clicks forward. With a normal Housai setup, the full-rich is WAY rich and full lean is running but will surge.
Typical for me, takeoff with a Housai is not full-rich but for higher altitudes but only a little forward (lean) of full rich.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=423067#423067
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