Throttle - don't let friction go unattended

[Boilermonkey]

For about a month we started noticing the throttle becoming a bit harder to move in and out on our M20C.  We thought, we'll get to it shortly at annual.  And then on one flight it got real sticky.

Upon landing and taxi it wouldn't advance, so I slowly limped back to the hangar at idle.  Upon further inspection you can see how bad the cable had frayed.  

Lesson:  If something is a bit wrong, get it fixed or looked at...it will only get worse, not better.   (could have happened in flight)

 

[Skates97]

Glad it happened on the ground. Is that an original cable?

As a PSA, I would recommend replacing the mixture and prop cables as well if they are just as old.

[jamesm]

also watch the other end  the Throttle cable where it mounts to bracket (aluminum angle) coming off the prop governor (oil pump) held  on by AN742-x metal clamp. that can slip allowing partial power on landing. Later I realize that other Mooney's of the same vintage had cross wrapping the throttle cable sheath ( housing) with safety wire to prevent the  throttle cable sheath from slipping in the AN742 clamp.

[carusoam]

Great pirep BM!

Engine controls have been known to be disappointing…

It is normal to swap them out at the time of the engine OH…

They may give some hints, but not much of a hint… before failure…

 

Next steps… owner supplied parts and macfarlane are in your future…  

 

Thanks for sharing the pics.

Best regards,

-a-

 

[EricJ]

I'm glad when the timing of these failures is fortuitous like that, especially when it fails at home.   Glad you found it and got it fixed!

 

[jaylw314]

+1 to happening on the ground and glad you're ok!

14 hours ago, carusoam said:

Engine controls have been known to be disappointing…

Sometimes -a- says things that crack me up for reasons I can't explain 

[Shadrach]

On 2/14/2022 at 4:54 PM, Skates97 said:

Glad it happened on the ground. Is that an original cable?

As a PSA, I would recommend replacing the mixture and prop cables as well if they are just as old.

I couldn’t say off the top of my head how old my cables are but I can tell you their condition (good) and that they were lubed in October.

[Ragsf15e]

1 hour ago, Shadrach said:

I couldn’t say off the top of my head how old my cables are but I can tell you their condition (good) and that they were lubed in October.

Only curious because you mentioned it… mine say not to apply lubricant, are there different versions that do need lubed?

[Boilermonkey]

I was told after the fact, that lubrication should not be used because it attracts particles and keeps them in the shaft.  If there is no lubrication and it becomes difficult to move, that means it's beginning to deteriorate and needs to be replaced. Application should be used, in this instance, wink.

[A64Pilot]

Some cables are all metal and should be lubed, ones we used on the Garrett powered Thrush even had zirc fittings.

Some cables have a plastic lining sort of like nylon and those should not be lubed as the oil breaks down the plastic, the plastic is of course supposed to be the lube.

[Shadrach]

2 hours ago, Ragsf15e said:

Only curious because you mentioned it… mine say not to apply lubricant, are there different versions that do need lubed?

I can’t say. An IA we knew many years ago made very small openings at a high point on the cable sheaths. They get lubed with mouse milk annually.  They all run smoothly across their full range of travel.  I’ve learned something today. I did not know that lubricating was not recommended. It’s been part of the annual SOP since before I started flying this plane. Perhaps we need to reassess our SOP.

[RobertGary1]

3 hours ago, Boilermonkey said:

I was told after the fact, that lubrication should not be used because it attracts particles and keeps them in the shaft. 

That is literally why they invented TriFlow

-Robert

[A64Pilot]

I’m trying to remember the name of the product, came in a can with a tip you put a long needle on, shook the can, it had a ball in it like a paint can to mix the graphite with the solvent, insert the needle into the end of the cable and squeezed. Made specifically for cables. Solvent flashed off leaving the graphite.

Used on motorcycle cables back in the 70’s, anyone remember it?

Found it, called Dr-slide,  not in a can anymore, best cable lube there is, and it dries out and won’t attract dirt, maybe it’s Moly Be Damn and not Graphite?

https://www.revzilla.com/motorcycle/dri-slide-bike-aid-film-lubricant?gclid=Cj0KCQiA3rKQBhCNARIsACUEW_bud2WVJRb5OPXYb6Ay6yT82TUGh1iyQ-rWTZdMWbB_7_MedAqEAu4aAguJEALw_wcB&sku_id=167170

Edited February 16, 2022 by A64Pilot

[RoundTwo]

16 minutes ago, A64Pilot said:

I’m trying to remember the name of the product, came in a can with a tip you put a long needle on, shook the can, it had a ball in it like a paint can to mix the graphite with the solvent, insert the needle into the end of the cable and squeezed. Made specifically for cables. Solvent flashed off leaving the graphite.

Used on motorcycle cables back in the 70’s, anyone remember it?

Found it, called Dr-slide,  not in a can anymore, best cable lube there is, and it dries out and won’t attract dirt, maybe it’s Moly Be Damn and not Graphite?

https://www.revzilla.com/motorcycle/dri-slide-bike-aid-film-lubricant?gclid=Cj0KCQiA3rKQBhCNARIsACUEW_bud2WVJRb5OPXYb6Ay6yT82TUGh1iyQ-rWTZdMWbB_7_MedAqEAu4aAguJEALw_wcB&sku_id=167170

Great stuff! Used it for years.

[Shadrach]

4 hours ago, A64Pilot said:

Some cables are all metal and should be lubed, ones we used on the Garrett powered Thrush even had zirc fittings.

Some cables have a plastic lining sort of like nylon and those should not be lubed as the oil breaks down the plastic, the plastic is of course supposed to be the lube.

My cables are all wire wound with an outer sheath. No deterioration of the plastic on my cables, we’d know by now.

[Shadrach]

1 hour ago, A64Pilot said:

I’m trying to remember the name of the product, came in a can with a tip you put a long needle on, shook the can, it had a ball in it like a paint can to mix the graphite with the solvent, insert the needle into the end of the cable and squeezed. Made specifically for cables. Solvent flashed off leaving the graphite.

Used on motorcycle cables back in the 70’s, anyone remember it?

Found it, called Dr-slide,  not in a can anymore, best cable lube there is, and it dries out and won’t attract dirt, maybe it’s Moly Be Damn and not Graphite?

https://www.revzilla.com/motorcycle/dri-slide-bike-aid-film-lubricant?gclid=Cj0KCQiA3rKQBhCNARIsACUEW_bud2WVJRb5OPXYb6Ay6yT82TUGh1iyQ-rWTZdMWbB_7_MedAqEAu4aAguJEALw_wcB&sku_id=167170

The question is how does dirt get into a coated, metal wound cable housing?

[AH-1 Cobra Pilot]

2 hours ago, A64Pilot said:

I’m trying to remember the name of the product, came in a can with a tip you put a long needle on, shook the can, it had a ball in it like a paint can to mix the graphite with the solvent, insert the needle into the end of the cable and squeezed. Made specifically for cables. Solvent flashed off leaving the graphite.

Used on motorcycle cables back in the 70’s, anyone remember it?

Found it, called Dr-slide,  not in a can anymore, best cable lube there is, and it dries out and won’t attract dirt, maybe it’s Moly Be Damn and not Graphite?

https://www.revzilla.com/motorcycle/dri-slide-bike-aid-film-lubricant?gclid=Cj0KCQiA3rKQBhCNARIsACUEW_bud2WVJRb5OPXYb6Ay6yT82TUGh1iyQ-rWTZdMWbB_7_MedAqEAu4aAguJEALw_wcB&sku_id=167170

38 minutes ago, Shadrach said:

The question is how does dirt get into a coated, metal wound cable housing?

Gremlins piss in it.

[Shadrach]

1 hour ago, AH-1 Cobra Pilot said:

Gremlins piss in it.

I thought they preferred K model breather tubes...

[Boilermonkey]

I'm pretty sure the throttle cable was the OEM from 1962.  With 4000hours and the hole for the gear warning, I'm sure crap got in there little by little.

Of course it could be fatigue.  It has started to fray and my guess is that years of pushing full throttle took their toll.  Probably more likely than contamination.   ...and lube won't help.

It was the last thing I fixed before handing over the keys and getting our M20M.  I did however go flying with the current owner last week.... nostalgia.

[A64Pilot]

Likely the failure mechanism began with corrosion

[A64Pilot]

6 hours ago, Shadrach said:

My cables are all wire wound with an outer sheath. No deterioration of the plastic on my cables, we’d know by now.

I’m speaking of the inside, most regular cables are multi strand wire running inside of a metal sheath, most often just wrapped steel, often plastic coated to keep dirt and water out. Bicycle and motorcycles cables for instance, some have a plastic liner to slide on and older designs don’t.

Often times the metal sheath has an interior plastic lining that the wire cable runs inside of, those shouldn’t be lubricated.

Some aircraft cables are teleflex cables, they are used when accuracy and repeatability are required, a teleflex cable is used, I doubt any of ours are teleflex, often used in helicopters. a teleflex can push as well as pull, think boat steering.

Second cable shows the plastic liner like I’m speaking of, the boat guy lead the way in cable manufacturing as you can imagine and the Thrush control cables are manufactured by a boat cable manufacturer in Florida, if your cable can live for years in a boat in salt water. then an airplane is easy.

Pretty much it’s the old design cables that can and should be lubricated where they new design ones shouldn’t. I’d assume most of ours, especially on older aircraft are of the type that can and should be lubricated.

 

 

Edited February 16, 2022 by A64Pilot

[Shadrach]

2 hours ago, A64Pilot said:

Likely the failure mechanism began with corrosion

My thought as well.

[Ragsf15e]

On 2/15/2022 at 7:39 PM, Shadrach said:

I can’t say. An IA we knew many years ago made very small openings at a high point on the cable sheaths. They get lubed with mouse milk annually.  They all run smoothly across their full range of travel.  I’ve learned something today. I did not know that lubricating was not recommended. It’s been part of the annual SOP since before I started flying this plane. Perhaps we need to reassess our SOP.

So I looked today and my throttle says don’t lube, the other 2 don’t say anything.  Throttle is a 2 year old mcfarlane cable from Mooney.

[LANCECASPER]

On 2/14/2022 at 3:52 PM, Boilermonkey said:

For about a month we started noticing the throttle becoming a bit harder to move in and out on our M20C.  We thought, we'll get to it shortly at annual.  And then on one flight it got real sticky.

Upon landing and taxi it wouldn't advance, so I slowly limped back to the hangar at idle.  Upon further inspection you can see how bad the cable had frayed.  

Lesson:  If something is a bit wrong, get it fixed or looked at...it will only get worse, not better.   (could have happened in flight)

 

Thankfully you weren't in the air

 

[A64Pilot]

1 hour ago, Ragsf15e said:

So I looked today and my throttle says don’t lube, the other 2 don’t say anything.  Throttle is a 2 year old mcfarlane cable from Mooney.

My bet is they don’t want you lubing the friction part, the why is self explanatory.

Ref it happening in the air at full throttle, I bet I could lean mine until it produced little power, especially with the RPM at the bottom of the green, maybe only one mag too, or would that be self defeating being so lean?

I’d much prefer stuck full on as opposed to lean, I’ve even seen aircraft with springs on the throttle lever with the idea of if the cable breaks the spring pulls it to wide open

I’m going out on a limb and guess the really old cables are all metal and would likely benefit from a little lube every now and again, but the newer ones maybe not. I know mine on the 140 are, and they get lubed once in awhile. Might ought to get some Dri-Slide now that I remember it.

I bet a call to Mcfarlane would confirm the presence or absence of an internal plastic sleeve.

Edited February 18, 2022 by A64Pilot