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Prolonged idling/taxiing

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1906

Joined: 30 Nov 2018
Posts: 58

Posted: Wed Oct 09, 2019 3:08 pm Post subject: Prolonged idling/taxiing

The M14P manual warns against prolonged idling which could cause "oiling" and probably spark plug fouling. If you are in this situation, forced to idle/taxi for some 15 minutes or more, what's the best course of action? Question for both scenarios - before a shutdown or before a takeoff.



Thanks.

markbitterlich(at)embarqm
Guest

Posted: Thu Oct 10, 2019 9:37 am Post subject: Prolonged idling/taxiing

If you are talking about what I *THINK* you are .... at idle the sump return

pump will not be spinning fast enough to return all the oil back to the

tank.  There should be a comment somewhere in the aircraft operating manual

that recommends that you run the engine  up to about 60-70% (pulling that

number from memory) for about 30 seconds or so, before shut down.  The same

applies to long sitting times at idle while waiting for the tower.  Simply

run the engine up for 30 seconds or so, and problem solved. 



Mark

--

1906

Joined: 30 Nov 2018
Posts: 58

Posted: Thu Oct 10, 2019 2:03 pm Post subject: Re: Prolonged idling/taxiing

Thank you Mark. That is what I thought but wanted to double check.

Ttail

Joined: 24 Jun 2013
Posts: 120

Posted: Thu Oct 10, 2019 3:06 pm Post subject: Re: Prolonged idling/taxiing

Are you referring to Plug fouling ? 



I see this quite often on an Auto converted  M14PF. As soon as a see a cylinder starting to go backwards CHT wise a run up is needed to clear the offending plug.



For me this is an issue any time their is extended taxi times and or holding before take off.

stephen.hayne

Joined: 01 Nov 2013
Posts: 59
Location: United States

Posted: Sat Oct 12, 2019 11:35 am Post subject: Re: Prolonged idling/taxiing

If plug fouling is the concern, this can be "fixed" by decoupling the mixture from the throttle, and leaning aggressively on the ground.  Takes about an hour, and some people reverse the arm on the carb so that it operates like a US mixture.  After 80 hours unreversed, and making one almost mistake on a go-around (pushing everything forward), I think I going to do mine that way.

_________________
-
Stephen Hayne, Cyber Security Consultant, Professor Emeritus (retired)
443LM Nanchang CJA
http://selfsynchronize.com/hayne/plane/cj6.asp

markbitterlich(at)embarqm
Guest

Posted: Sat Oct 12, 2019 1:07 pm Post subject: Prolonged idling/taxiing

Good advice, but M14P's do not generally come equipped with a manual mixture

control.  



Mark

--

stephen.hayne

Joined: 01 Nov 2013
Posts: 59
Location: United States

Posted: Sat Oct 12, 2019 1:27 pm Post subject: Re: Prolonged idling/taxiing

Sorry! I had CJ and Housai on the brain...

_________________
-
Stephen Hayne, Cyber Security Consultant, Professor Emeritus (retired)
443LM Nanchang CJA
http://selfsynchronize.com/hayne/plane/cj6.asp

AlaskaChang801

Joined: 26 Jan 2018
Posts: 36

Posted: Sun Oct 13, 2019 10:36 am Post subject: Re: Prolonged idling/taxiing

 	  stephen.hayne wrote: 	
		  If plug fouling is the concern, this can be "fixed" by decoupling the mixture from the throttle, and leaning aggressively on the ground.  Takes about an hour, and some people reverse the arm on the carb so that it operates like a US mixture.  After 80 hours unreversed, and making one almost mistake on a go-around (pushing everything forward), I think I going to do mine that way. 	




So you bring up a question I've had for a while now and quite honestly, I've been happy to be ignorant on the situation. So I think it's time to clarify this for me. 

I bought my CJ and it had been modified in the way you mentioned. So when I go forward on my mixture lever I'm going to FULL Rich. I typically run mine forward for "start" and pull it back about half way for taxi. Full forward for the run up and takeoff. Then I'm pulling it back to about half way or a little further for cruise. Again forward for landing and half back after rollout and up to parking.

So my question is ?? Is this an ok way to run it? with not having a EGT to monitor I'm cautious of pulling to far Lean and have been warned not to so that I don't burn up the exhaust valves. 

Also, how far back should I bring it for cruise and should I adjust that based on cruise altitude. Again not having an EGT how do I determine what's safe and not leaning out too much.



Thanks for your input

stephen.hayne

Joined: 01 Nov 2013
Posts: 59
Location: United States

Posted: Sun Oct 13, 2019 4:42 pm Post subject: Re: Prolonged idling/taxiing

This is a bit tricky to answer, because it depends on how the "cruise" mixture screw has been set, and how the "idle" mixture screw has been set.  There are manual pages describing how to set these, but at 5000', I was running too rich at idle.  So, I turned the idle "in" (righty tighty), 3 clicks.  Seems better.



Then I did the same for the "cruise" screw (before installing an MGL FF3).  Then, at pattern altitude, on downwind, I would "push" (or pull in your case), the mixture forward until I got noticeable power/speed reduction.  Engine won't fail, or sputter, but it will just "fade".  If that happened when I was almost at the stop, I feel like that is good, because then I can lean quite a bit at altitude for cruise.



After installing the FF3, I now lean for about 2.6gph at idle (noticeable idle rpm rise), and then for whatever the book calls for at cruise, plus just a little because it seems to be too slow at those gph... 



I don't think you can hurt the engine much, since it is carbureted.  Tough to get too "lean of peak".  Read up about the 182 and "lean of peak" if you want a controversy.



You are likely at sea level, so I think that full rich at TO and LDNG is very smart.



But, I think you can play with the settings a bit (clicks) and if you can get the engine to significantly slow just as you get to full lean, then you might be in the sweet spot.  Look for an RPM rise, an inch before getting to full lean, maybe?

_________________
-
Stephen Hayne, Cyber Security Consultant, Professor Emeritus (retired)
443LM Nanchang CJA
http://selfsynchronize.com/hayne/plane/cj6.asp

AlaskaChang801

Joined: 26 Jan 2018
Posts: 36

Posted: Tue Oct 15, 2019 6:26 pm Post subject: Re: Prolonged idling/taxiing

 	  stephen.hayne wrote: 	
		  This is a bit tricky to answer, because it depends on how the "cruise" mixture screw has been set, and how the "idle" mixture screw has been set.  There are manual pages describing how to set these, but at 5000', I was running too rich at idle.  So, I turned the idle "in" (righty tighty), 3 clicks.  Seems better.



Then I did the same for the "cruise" screw (before installing an MGL FF3).  Then, at pattern altitude, on downwind, I would "push" (or pull in your case), the mixture forward until I got noticeable power/speed reduction.  Engine won't fail, or sputter, but it will just "fade".  If that happened when I was almost at the stop, I feel like that is good, because then I can lean quite a bit at altitude for cruise.



After installing the FF3, I now lean for about 2.6gph at idle (noticeable idle rpm rise), and then for whatever the book calls for at cruise, plus just a little because it seems to be too slow at those gph... 



I don't think you can hurt the engine much, since it is carbureted.  Tough to get too "lean of peak".  Read up about the 182 and "lean of peak" if you want a controversy.



You are likely at sea level, so I think that full rich at TO and LDNG is very smart.



But, I think you can play with the settings a bit (clicks) and if you can get the engine to significantly slow just as you get to full lean, then you might be in the sweet spot.  Look for an RPM rise, an inch before getting to full lean, maybe? 	


Thanks for the info and advice. I guess I've got to dig in a little deeper and figure out what my mixture screws are set at and start from there.

stephen.hayne

Joined: 01 Nov 2013
Posts: 59
Location: United States

Posted: Wed Oct 16, 2019 8:09 am Post subject: Re: Prolonged idling/taxiing

Here are some links to the manual pages for adjusting these screws... (and the Fuel Flow that I installed).



https://drive.google.com/drive/folders/1DKFaSiQNhG2ar0QLg8qSlwTcU99xpqT2?usp=sharing

_________________
-
Stephen Hayne, Cyber Security Consultant, Professor Emeritus (retired)
443LM Nanchang CJA
http://selfsynchronize.com/hayne/plane/cj6.asp

markbitterlich(at)embarqm
Guest

Posted: Wed Oct 16, 2019 10:18 am Post subject: Prolonged idling/taxiing

Something worth knowing that is not necessarily explained in task cards for M-14 carb adjustments is that a lot of cooling for the engine is provided by fuel, which is why they are often adjusted rich on purpose. That and the fact that CHT's vary significantly from one to the next in flight. Adjusting carb mixture screws should be approached with caution. 



Mark

-------- Original message --------

From: "stephen.hayne" <stephen.hayne(at)gmail.com> 

Date: 10/16/19  12:09  (GMT-05:00) 

To: yak-list(at)matronics.com 

Subject: Yak-List: Re: Prolonged idling/taxiing 



--> Yak-List message posted by: "stephen.hayne" <stephen.hayne(at)gmail.com>



Here are some links to the manual pages for adjusting these screws... (and the Fuel Flow that I installed).



https://drive.google.com/drive/folders/1DKFaSiQNhG2ar0QLg8qSlwTcU99xpqT2?usp=sharing



--------

-

Stephen Hayne, Professor, CIS, Colorado State University

666CJA 

 http://selfsynchronize.com/hayne/plane/cj6.asp





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AlaskaChang801

Joined: 26 Jan 2018
Posts: 36

Posted: Fri Oct 18, 2019 4:30 pm Post subject: Re: Prolonged idling/taxiing

Thanks for the links. Will do some research into mine.

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