Mixture cable fell off

[jetdriven]

So me and my airplane partner went for a little airplane ride to show him some Chandelles and Lazy-8s.  Finished those and decided to head back and do a few landings with these new brakes.  Now he had the mixture back dang near to idle cutoff to get it to lean down, and thats a lot more than usual. Entering the pattern the engine was running OK but popping a lot out the exhaust even with the mixture full rich. Seemed a little odd but it was still running good, perhaps a little down on power.  Taxied back to have  another go at it and decided to check it out and do another runup. Mag drop was 250 RPM. Now, WTF, both of those are new, and BOTH of them are acting up?  Looked at the  EGT and it as showing 1500 degrees at 2000 RPM. That's not right either.  Reached over to fool with the mixture and went full rich, half back, and then to cutoff. EGT still 1500 degrees.   OK, I suppose we are done for the day.

 

This is what we found.   That plug backed completely out the end of the mixture cable and it fell off the ball on the fuel injection servo. That's strange as it has flown 5000 hours and I personally put that new engine on myself, 175 hours ago.   Next time you got the cowling off, check the cotter pin on that fitting. It could have been bad, but instead I'm having a beer.

 

 

(fixed now)

[kerry]

My mixture cable broke a couple years ago.  Luckily for me it happend on start up when I pushed mixture to full rich.

[Alan Fox]

You are one very very lucky guy.......Go buy a lottery ticket.....

[yvesg]

Why did this happen? Was the cotter pin missing?

Yves

[N201MKTurbo]

I replaced that ball and socket with a rod end on both of my Mooneys. I hate that cheap little fitting. Rig it just like the throttle cable.

[Alan Fox]

I replaced that ball and socket with a rod end on both of my Mooneys. I hate that cheap little fitting. Rig it just like the throttle cable.

I think a washer on the end is required for the rod end , but much safer than the ball socket...

[N601RX]

I have rod ends on mine also.

[DS1980]

Here's my control failure. Happened on the ground as well. I thought the carb had a return spring attached to pull the mixture to full rich if this happens. It doesn't. I consider these cables to be age limited. The TTAF was 2600.

[DaV8or]

Is this true for the fuel injected engines too? I thought they would default to full rich, am I wrong?

[jetdriven]

The mixture stayed right where it was when it fell off, about halfway between full rich and ICO.  There is enough friction in the bearings or seals in the fuel servo unit that it didnt move after it was disconnected.  It could have vibrated to another position over time however.

[Alan Fox]

They do not default , you could probably install an "illegal" spring as a backup...

[fantom]

I replaced that ball and socket with a rod end on both of my Mooneys......Rig it just like the throttle cable.

Excellent suggestion. Another item on the 'to do' list

You and your partner were lucky, Byron.

[Bennett]

Suggestion: While you are checking cables, check your throttle and propeller cables as well.  I had a throttle cable break off on takeoff some years ago. It was in the 261, and it was my habit to start with full boosted MP, and pull back an inch or two as the aircraft accelerated down the runway to avoid overboost. After liftoff and at about 50' or so, I pulled back "a bit" more on the throttle as boost was still near redline, and the knob and an inch or two of the cable top came off in my hand. Killed the mixture and managed to get back on the ground, on the brakes -hard, and managed to stop at the very end of the runway.  This was at Little River, CA, which is 5,280' long. My home airport, KSQL, is 2,600' long, so I consider myself very lucky that the cable broke where and when it did.  As I recall, the weld at the end of the cable, where it meets the knob mechanism (solid rod) broke. No warning, it just broke, and without undue pressure. I have often thought about what I would have done, had the aircraft been much higher, or if it broke when preparing to land. 

[PTK]

Is there a kit of some sort to convert to rod end? Part numbers?

Thank you for the heads up Byron. I love what LOP ops do for my engine...but not that much!

I guess the cotter pin just fatigued and failed allowing that threaded plug to back out.

[DS1980]

Is it possible to get a field approval/STC for a return spring?

[jetdriven]

Is it possible to get a field approval/STC for a return spring?

I dont think it would work on a lever mixture, the spring would pull the mixture to rich unless you clamped down on the friction lock all the time. It might work for a vernier mixture because those lock the cable. Either way, I don't think it's needed as long as that plug and the stud are cotter pinned.

[Alan Fox]

Is there a kit of some sort to convert to rod end? Part numbers?

Thank you for the heads up Byron. I love what LOP ops do for my engine...but not that much!

I guess the cotter pin just fatigued and failed allowing that threaded plug to back out.

I think he means the pin on the ball itself which is steel , and not a kotter..... The way to convert it is to get a standard rod end , Bob has them , and install it with standard AN hardware with a flat washer on the open end , so if the rod end fails , the washer holds it on......

[jetdriven]

Check the photos again. The ball is intact. The plug on the end of the cable unscrewed itself and fell out, which allowed the ball to come out of the socket and disconnect. Perhaps this is why we have had so much trouble getting a good GAMI spread to send to John-Paul. The ball must have been pretty loose in the socket lately. We noticed the mixture drifts around a lot when trying to nail down the GAMI spread numbers.

[DS1980]

For mine, the actual cable broke. The fitting at the carb was fine. Makes me wonder the bending/torsional stress that's always on the cable and if it fatigues it over time regardless of how often it is used.

[KSMooniac]

Good thing you didn't need to do a go-around.

[jetdriven]

It was sounding funny and I did firewall it on base to check it. It made almost full power but would have gotten warm pretty quick.

[Flymac]

Old post but same topic/issue as my mechanic and i are in the middle of re-attaching mixture cable to servo...just not happy with how it binds up slightly on the mixture cutoff end...he played with the rod end for awhile, checked service book and saw how it has that mooney part mentioned above and thought that was issue and having “correct” part would mechanically link up better and deal with the angle more smoothly...well after researching this thread and others, seems everyone is doing the opposite and getting rid of that link ha!  So i think we are best off with the rod end, but its just so crappily spaced/shimmed/angled that needs fixed, or maybe a different one...does anyone have any pics of your your installation and how your cable is attached to the engine standoff? See mine, its such an angle but manual does show having cable on outside...not a fan of all the washers for spacing either, but then the angle of the rod to the rod end would be even worse...appreciate any comparison

Edited December 8, 2018 by Flymac

[carusoam]

Looks like...

• the arm might not be the right one for the job...
• the nut holding the arm on could be better... safety wire or is it a locking nut?

In this case... if you don’t get an MS answer... (you will probably get several)

• Dan @ Lazar will have you covered.
• For solid answers on how engine parts are supposed to be connected... @M20Doc.

Having engine controls fail has got to be an empty feeling.

Best regards,

-a-

[N201MKTurbo]

You might want to adjust the arm position. The arm has notches so you can change its position. I would move it one notch clockwise.

[Andy95W]

53 minutes ago, N201MKTurbo said:

You might want to adjust the arm position. The arm has notches so you can change its position. I would move it one notch clockwise.

What Rich said, above.  Also, it almost looks like the mixture and ram air control cables mounting locations got swapped over the years.  That would get rid of all the extra washers.  It will be nice to see somebody else's pictures.