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Tunahawk
Joined: 24 Dec 2013
Posts: 9
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 Posted: Sat Jul 26, 2014 7:17 am Post subject: Re T/s Assist |
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Team Hi,
Need some insight/assistance into an issue we are having with our , O-320, High Compression STC,Power Flow Equipped, 77 Cheetah. After touchdown and roll out our engine will quit unless throttle is cracked open a bit, (we fly out of KSGJ so basically a sea level airport), no issues with restarting it. Typical scenario is on final with power minimum (throttle closed) , mixture full rich, carb heat OFF. After touchdown, usually while turning off runway, speed < 20 knots (guess) and pulling off the runway the engine wants to quit (and has) unless some throttle is applied. Our mechanic has checked engine at low idle RPM (normal range (600-800?at idle). Hes also checked the idle cutoff rise at idle of ~ 50 rpm.
The other day we ran at idle after start for longer than normal with no problem. So this problem only seems to appear after engine is hot and after touchdown.
Any suggestions or experiences such as this?
Thanks
Cheers,
Bill
N26114 KSGJ
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BARRY CHECK 6
Joined: 15 Mar 2011
Posts: 738
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| Posted: Sat Jul 26, 2014 7:50 am Post subject: Re T/s Assist |
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Very good report Bill:
Things that I would check - And these are NOT in order of severity:
1 - Engine temps - Are you seeing high CHT's? Does the lower part of the engine/cowl feel hotter than normal. Crazy thought - Could you be approaching vapor lock. Yes. vapor lock can happen even with AvGas.
2 - Mixture Cable - For smooth operation and full movement.
3 - Mixture Cable - For mounting and cable supports.
4 - Throttle Cable - Same as Mixture Cable above.
4a - With these checks you are also LQQKing for unwanted movement - Too free a movement.
5 - Carb - Any air leaks - Mounting.
6 - Carb Box - Any thing loose
7 - Carb Heat - Is it moving when you do not want it to?
8 - Carb Heat Cable - You got it - For smooth operation and full movement. For mounting and cable supports.
9 - Fuel Pressure - Is it dropping when you go to idle... More than allowed, out of the Green Arc?
10 - Air filter - Anything blocking the air filter.
Note: I would NOT do any power off stalls until you solve this problem.
Please report back on what you find.
Barry
On Sat, Jul 26, 2014 at 11:17 AM, Bill Chambers <metuna(at)earthlink.net (metuna(at)earthlink.net)> wrote:
[quote] Team Hi,
Need some insight/assistance into an issue we are having with our , O-320, High Compression STC,Power Flow Equipped, 77 Cheetah. After touchdown and roll out our engine will quit unless throttle is cracked open a bit, (we fly out of KSGJ so basically a sea level airport), no issues with restarting it. Typical scenario is on final with power minimum (throttle closed) , mixture full rich, carb heat OFF. After touchdown, usually while turning off runway, speed < 20 knots (guess) and pulling off the runway the engine wants to quit (and has) unless some throttle is applied. Our mechanic has checked engine at low idle RPM (normal range (600-800?at idle). Hes also checked the idle cutoff rise at idle of ~ 50 rpm.
The other day we ran at idle after start for longer than normal with no problem. So this problem only seems to appear after engine is hot and after touchdown.
Any suggestions or experiences such as this?
Thanks
Cheers,
Bill
N26114 KSGJ
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teamgrumman(at)yahoo.com
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| Posted: Sun Jul 27, 2014 2:39 pm Post subject: Re T/s Assist |
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I had a similar problem with a Cheetah.
Barry's comment about fuel pressure is a good one the investigate.
What I did was to send the carb to LyCon and have them flow test the carb and repair as necessary. I don't recall the exact fix but whatever it was, it solved the problem.
On my website, I have IDLE mixture setting instructions. Look under Technical Stuff. Most mechanics do not know how to set the IDLE/Mixture.
I usually set the IDLE to the lowest limits. This way, when landing, the engine isn't pulling.
On a Tiger, I shoot for 500 rpm or less. On a Cheetah, 600 rpm or less.
On N28747, the IDLE was set at 450rpm. Never had any problems. LyCon did my carb too.
Bring it here and I'll set it up for you.
Gary
On Saturday, July 26, 2014 9:00 AM, FLYaDIVE <flyadive(at)gmail.com> wrote:
Very good report Bill:
Things that I would check - And these are NOT in order of severity:
1 - Engine temps - Are you seeing high CHT's? Does the lower part of the engine/cowl feel hotter than normal. Crazy thought - Could you be approaching vapor lock. Yes. vapor lock can happen even with AvGas.
2 - Mixture Cable - For smooth operation and full movement.
3 - Mixture Cable - For mounting and cable supports.
4 - Throttle Cable - Same as Mixture Cable above.
4a - With these checks you are also LQQKing for unwanted movement - Too free a movement.
5 - Carb - Any air leaks - Mounting.
6 - Carb Box - Any thing loose
7 - Carb Heat - Is it moving when you do not want it to?
8 - Carb Heat Cable - You got it - For smooth operation and full movement. For mounting and cable supports.
9 - Fuel Pressure - Is it dropping when you go to idle... More than allowed, out of the Green Arc?
10 - Air filter - Anything blocking the air filter.
Note: I would NOT do any power off stalls until you solve this problem.
Please report back on what you find.
Barry
On Sat, Jul 26, 2014 at 11:17 AM, Bill Chambers <metuna(at)earthlink.net (metuna(at)earthlink.net)> wrote:
[quote] Team Hi,
Need some insight/assistance into an issue we are having with our , O-320, High Compression STC,Power Flow Equipped, 77 Cheetah. After touchdown and roll out our engine will quit unless throttle is cracked open a bit, (we fly out of KSGJ so basically a sea level airport), no issues with restarting it. Typical scenario is on final with power minimum (throttle closed) , mixture full rich, carb heat OFF. After touchdown, usually while turning off runway, speed < 20 knots (guess) and pulling off the runway the engine wants to quit (and has) unless some throttle is applied. Our mechanic has checked engine at low idle RPM (normal range (600-800?at idle). Hes also checked the idle cutoff rise at idle of ~ 50 rpm.
The other day we ran at idle after start for longer than normal with no problem. So this problem only seems to appear after engine is hot and after touchdown.
Any suggestions or experiences such as this?
Thanks
Cheers,
Bill
N26114 KSGJ
| Quote: |
st" target="_blank">http://www.matronics.com/Navigator?TeamGrumman-List
tp://forums.matronics.com
_blank">http://www.matronics.com/contribution
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http://www.matro====================
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Tunahawk
Joined: 24 Dec 2013
Posts: 9
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| Posted: Tue Oct 21, 2014 12:10 pm Post subject: Re: Re T/s Assist |
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Quick followup, We did the setup per Gary's info, seem to run okay afterwards but had issues and rough running on a second subsequent flight.
Problem was resolved by installing an overhauled carburetor from Kelly Aerospace , BTW make sure you get the carb with any mounting ports for instrumentation, ours a JPI carb temp probe. First one had a plugged hole that could have been machined but we didn't want to mess with it.
Kelly took care of us by sending one with temp probe port already machined in after we returned the first one we got.
Our old carb (an O/H) had been installed seven years ago.
Thanks for the help!!
Cheers,
N26114 KSGJ
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| Posted: Wed Oct 22, 2014 10:17 am Post subject: Re T/s Assist |
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Here is an interesting side note to the carburetor issue.
All 3 factory overhauled engines (O360-A4K) that I've installed in the last couple of years I've sent to LyCon for port & polish. 2 of the engines I had torn down, inspected, and had the case "O" ringed.
On each of the engines, there were carburetor metering problems. Ken returned the carbs to ? (I forget) to get them corrected. One carb, for 28219, could not be fixed after returning it 3 times. Ken ended up using one of his carbs so he could deliver the engine.
Whoever is making (actually fabricating) the carburetors has screwed up the original design.
I'm glad to hear your Cheetah is happy again.
Gary
From: Tunahawk <metuna(at)earthlink.net>
To: teamgrumman-list(at)matronics.com
Sent: Tuesday, October 21, 2014 1:10 PM
Subject: Re: Re T/s Assist
--> TeamGrumman-List message posted by: "Tunahawk" <metuna(at)earthlink.net (metuna(at)earthlink.net)>
Quick followup, We did the setup per Gary's info, seem to run okay afterwards but had issues and rough running on a second subsequent flight.
Problem was resolved by installing an overhauled carburetor from Kelly Aerospace , BTW make sure you get the carb with any mounting ports for instrumentation, ours a JPI carb temp probe. First one had a plugged hole that could have been machined but we didn't want to mess with it.
Kelly took care of us by sending one with temp probe port already machined in after we returned the first one we got.
Our old carb (an O/H) had been installed seven years ago.
Thanks for the help!!
Cheers,
N26114 KSGJ
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