M20C Throttle Cable not in usual position!!!

[Janat83]

Hello Mooniacs 

Today I was flying, everything was normal, when I started my descend I pulled the throttle to 22" of MP as I usually do on descend, and I slowly started to pull the throttle out as I was getting close to the airport, when I get the MP to show 20" my landing gear horn went off (this usually happen at 12"), and I noticed that my throttle cable was a little bit out more than usually for that power settings, I slowed down and put the landing gear down, on short final I noticed that my throttle cable is longer than usual but everything was fine and I landed with no issue. 

I took a picture for the throttle canble and the marked part doesn't seem to be familiar to me (this part used to be inside the panel), 

What could be the issue? 

I'll have my mechanic look at it next week. 

Thank you in advance for your guidance and thoughts. 

MOUSTAFA JANAT 

[carusoam]

Moustafa,

Control knobs not working properly is bad...

Looks like you may have a classic wear challenge for your control cables...

Something is falling apart...?

Check your logs to identify how old they really are.

There is a classic replacement solution documented around here as well.

The guidance for age for engine controls is generally matched to engine TBO....
 

You can start with visually inspecting both ends of the cable... looking for fraying or anything that is falling apart.

The important thing to consider... if a cable falls apart... you may not have control of the engine...
 

Check your logs for all three cables, inspect all three cables...

If you need new cables look up macfarlane, and follow the procedures for owner produced parts...

See if you can see what is on the other side of the panel... that is where the micro switch sensor rides along the the throttle shaft...

PP thoughts only, not a mechanic..

Best regards,

-a-

[kortopates]

Agree with Anthony above, I personally wouldn't fly it again till inspecting the control cable for throttle - you might find its on the verge of coming off or breaking and you were very lucky to get down before it did. But hopefully you or your mechanic will find something that's easy to fix. Not sure what you'll find, but they sure don't stretch! Let us know what you find.  

Edited July 30, 2020 by kortopates

[Jim Peace]

I had a MSC install a brand new throttle cable.....on the first test flight I landed and the cable disconnected form the carb.  Engine wound up and I decided to throttle the engine with the mixture so I could taxi the 2 miles back to the shop.....

took them weeks to get it right......also it always crept up on its own.......like an auto throttle.  all fixed now......took a Long time for them to hone in on it....more of a shop issue than anything else....

disappointing for the time and money spent........

[Yooper Rocketman]

I would be willing to bet the clamp on the outer cable at the carb attachment point is allowing the cable to slide.  When you pull the throttle towards idle that creates a pulling tension on the outer cable at that clamp.  Once it starts slipping it's only going to get worse.  If that's the actual culprit it could slip the other way too, not giving you any power at a point you need it.  As others have said, I wouldn't ever consider flying it until the problem is resolved.

Tom

[Janat83]

10 hours ago, Yooper Rocketman said:

I would be willing to bet the clamp on the outer cable at the carb attachment point is allowing the cable to slide.  When you pull the throttle towards idle that creates a pulling tension on the outer cable at that clamp.  Once it starts slipping it's only going to get worse.  If that's the actual culprit it could slip the other way too, not giving you any power at a point you need it.  As others have said, I wouldn't ever consider flying it until the problem is resolved.

Tom

My mechanich is looking at it right now, he found the nut at the panel lose, but that wasn't the main issue, he said the cable looked like it stretched and he's think the sleeve clamp is lose too. 

[Hank]

I'd guess the outer part is unwrapping some, making it longer. The loose clamp will move it, affecting movement of the throttle.

Suggestion:  replace the throttle cable. Check the prop.and mixture cables, too. Oh, also check your carb heat cable.

[carusoam]

Great pics Janat!

Best regards,

-a-

[Guest]

The cable anchor clamps should not have a rubber insert. Use AN742 series steel clamps.

Also in your fourth picture the fuel pressure hose on top of the carburetor appears to be low pressure instrument air hose from the fitting type I see.  Slip the fire sleeve back for a closer look.

Clarence

[Janat83]

On 7/30/2020 at 6:26 AM, Yooper Rocketman said:

I would be willing to bet the clamp on the outer cable at the carb attachment point is allowing the cable to slide.  When you pull the throttle towards idle that creates a pulling tension on the outer cable at that clamp.  Once it starts slipping it's only going to get worse.  If that's the actual culprit it could slip the other way too, not giving you any power at a point you need it.  As others have said, I wouldn't ever consider flying it until the problem is resolved.

Tom

My mechanic is looking into that today, we found the clamp rubber broken, will replace with MS21919-DG5 as in the service manual, I have a question about this part of the throttle cable, is it supposed to be like that or this sleeve is broken (I mean it looks it have an angle with the sleeve not straight) ? 

[Janat83]

On 7/31/2020 at 4:03 AM, M20Doc said:

The cable anchor clamps should not have a rubber insert. Use AN742 series steel clamps.

Also in your fourth picture the fuel pressure hose on top of the carburetor appears to be low pressure instrument air hose from the fitting type I see.  Slip the fire sleeve back for a closer look.

Clarence

Service manual says use MS21919-DG5, also here's a picture for that fuel line without sleeve. 

[N201MKTurbo]

5 minutes ago, Janat83 said:

My mechanic is looking into that today, we found the clamp rubber broken, will replace with MS21919-DG5 as in the service manual, I have a question about this part of the throttle cable, is it supposed to be like that or this sleeve is broken (I mean it looks it have an angle with the sleeve not straight) ? 

Yes, there is a ball formed on the end of the skinny tube. It is crimped into the larger socket by the indent that goes around it. It is meant to swivel.

[Guest]

44 minutes ago, Janat83 said:

Service manual says use MS21919-DG5, also here's a picture for that fuel line without sleeve. 

Mil-H-5593 type hose is meant for instrument air systems, pitot static and vacuum.  It does not do well with fuel, oil etc.

The cable as Rich points out is meant to swivel at the ball joint, most have a rubber seal to keep dirt out and prevent excessive vibration which wears the ball and socket.

Clarence

[Janat83]

2 hours ago, M20Doc said:

Mil-H-5593 type hose is meant for instrument air systems, pitot static and vacuum.  It does not do well with fuel, oil etc.

The cable as Rich points out is meant to swivel at the ball joint, most have a rubber seal to keep dirt out and prevent excessive vibration which wears the ball and socket.

Clarence

Yes the rubber seal is now in place and the clamp also in place the only issue now it that throttle knob doesn't go all the way in and gear horn is going off at 19", I can get used to the throttle knob position but we need to adjust the gear horn switch position. 

[Yooper Rocketman]

Where you clamp the outer cable housing in relationship to the actual throttle will effect the position the throttle knob will rest at fully pushed forward (and pulled back as well).  If you adjust the clamp position so full throttle has the knob resting all the way in, your gear horn may work like it did before.  "I believe" the gear horn switch is a throttle position sensor on the throttle cable behind the dash.  It should be adjustable at the sensor too, but getting the throttle adjustment back to original will likely fix the gear horn issue too.

Tom

 

[Rjfanjet]

I'd also look at replacing the rod end on the throttle. The one on there now is obsolete. LASAR has the replacement. I did mine the last annual.

[Janat83]

On 8/5/2020 at 6:11 AM, Yooper Rocketman said:

Where you clamp the outer cable housing in relationship to the actual throttle will effect the position the throttle knob will rest at fully pushed forward (and pulled back as well).  If you adjust the clamp position so full throttle has the knob resting all the way in, your gear horn may work like it did before.  "I believe" the gear horn switch is a throttle position sensor on the throttle cable behind the dash.  It should be adjustable at the sensor too, but getting the throttle adjustment back to original will likely fix the gear horn issue too.

Tom

 

Final update

today we re-adjust the position of the clamp and it did just like it originally was without adjusting the microswitch, I have put the throttle, mixture and prop cables on my to-do-list for next annual while the airplane. 

Thank you guys for the help

 

MOUSTAFA JANAT 

 

[M20F-1968]

I looked at only the first 1/2 of this thread and decided I had seen enough.....

This is without a doubt a safety of flight issue, REPLACE THE CABLE AND HARDWARE COMPLETELY and do not fly the plane until you do.  

Anything else is throwing good money after bad, and gambling and off airport landing, OR WORSE!

It looks like your other control cables are old and in need or attention (probable replacement) as well.

John Breda

[Janat83]

2 hours ago, M20F-1968 said:

I looked at only the first 1/2 of this thread and decided I had seen enough.....

This is without a doubt a safety of flight issue, REPLACE THE CABLE AND HARDWARE COMPLETELY and do not fly the plane until you do.  

Anything else is throwing good money after bad, and gambling and off airport landing, OR WORSE!

It looks like your other control cables are old and in need or attention (probable replacement) as well.

John Breda

Dear Jhon

Thank you for your comment, can you explain what's wrong you see here, my mechanic inspected all cables and said everything looking fine, I told him I want to replace the old cables he said I can do that but it's looking good so far and airworthy.

Kindly let me know if I'm missing anything here, If so I can bring that to his attention or find another mechanic to look at it.

Thank you very much in advance for your help! 

Moustafa Janat

Edited August 8, 2020 by Janat83

[M20F-1968]

Unless there is something obviously loose and recognizable, ie. the hardware at one end is loose, the outercable has slipped; here is nothing in the throttle cable assembly which should stretch or change.  The control, cables need to be 100% reliable, without exception.  There is also a useful life.  How long have they been in there?  Too many owners try to push things out and save some money, only to find that they have suddenly (and they think unexpectedly) lost control of their airplane when they had plenty of warning.  Flying is not an endeavor where one should allow unexplained events go un-noticed, particularly in systems with no room for error.  Noting what you did, and not finding a clear reason is allowing the problem to go un-noticed.  The explanation your mechanic gave, cable may have stretched, or it is OK, u=is not giving you and answer as to why the event has occurred. 

There are all sorts of mindsets and abilities in A&P mechanics out there.   Many of them i would not let near my airplane.  You want someone with high standards and a high level of suspicion.  You said your mechanic thought the cable had stretched; control cables do not stretch, they are not under sufficient load.  They do bind, fray and break, all are un-welcomed.  I would want to inspect the cable, but you can not since it is quite a bit of work to get it out.  It is simply easier and safer to replace it.  You do not want it coming apart in your hand at 10,000 leaving you unable to control power or be left with only a mixture control to do so.   Not worth the $500 bucks you might "save" only to cost you more in the end, or worse.  It is much easier to troubleshoot and work on an airplane when it is on the ground instead of in the air.

John Breda

[carusoam]

Modern maintenance schedules dictate...

Cables get replace at engine OH...

They typically look good up to the day they stop working...
 

We have had a few MSers report stuck controls... Or broken cables...

Even on newer Ovations...

So... if you like...   Change them every 2k hrs or so...

As John pointed out... their function is just too important to not change them...

Best regards,

-a-

 

[AKEllsworth]

  I am seeing similar issues with my cables. What is the best source for the throttle, mixture and propeller control cables.

1969 m20c  see pic for style. 

[PT20J]

McFarlane. If they don’t already have a part designed, you can send them the old one and they will design a replacement. My A&P recently had them do that for a Beech Sundowner. Took 4 weeks — 2 for the design and 2 to fabricate. 

Skip

[AKEllsworth]

Thank you Skip!

[carusoam]

4 hours ago, AKEllsworth said:

  I am seeing similar issues with my cables. What is the best source for the throttle, mixture and propeller control cables.

1969 m20c  see pic for style. 

This is a great parts request… sort of unique to control cables…

+1 for Skip’s explanation of how to best handle it today…

I’m going to invite a guy to see how common worn parts are replaced for Mooneys…

This individual knows something about Mooney parts supply… @Jonny

PP thoughts only, not an aviation parts guy…

Best regards,

-a-