Oxygen System Mechanical Problem

[Mooney217RN]

Need some help from the brain trust here at MS.

I flew to drop off supplies yesterday about 200 miles from home.  I went to turn on the O2, and the knob had no tension.  It just spun around.  Couldn't turn it on.  The set screw in the knob is secure.  This problem is part of the internal mechanism that turns the valve on/off.

Normally, I would have the best MSC on the west coast take care of this.  But these are not normal times - no rental cars, nobody willing to fly me back/forth so I can drop off and pick up the plane.

So...any ideas?  I was told that the pilot side panel had to be removed to see if the cable snapped or something else went awry.  This seems like a ton of work.  By the way, this was a sudden failure with no advance warning.  It just happened for no apparent reason.

So MS'ers - the challenge is on!  Give me a hand if you can.

[smwash02]

I posted a couple months ago of my similar plight with photos and a solution. Same as yours, no advanced warning, as far as I'm concerned it's a flaw in the design.

Ultimately you're going to need to take the pilot side interior out and fix it and it is even more work if your knob apparatus had the screw put in the wrong way like mine.

If you've got 10 minutes before and after each flight you can pop the tail panel and turn the regulator on and off by hand -- not a long term solution of course.

Another thread on here has the correct spring steel cable you will most likely need to resolve this. Mine didn't have enough slack left to re-wind on the peg.

[kortopates]

Not really that much of a challenge. Does sound like the cable has slipped off or broken off at an end. But you can't be sure which end yet. So suggest begin by confirming which end the problem is at by inspecting the avionics bay first since it has easy access.   Verify if the regulator arm moves freely there with the cable still attached.  Maybe you'll get lucky and find it disconnected at that end but probably not if you felt zero resistance at the knob.  But by doing that 10 min check first and verifying it  checks out okay, at least you know the problem is in the cockpit. Its not hard to remove the plastic panel there to get access there but you won't know what you need to fix it till you can see it and you could possibly need a new wire depending on what you find.

[carusoam]

In the event you didn’t see the pics SMW is describing...
 

Click on the word ‘posted’ in SMW’s last post... it goes directly to the pics of the O2 system...

I thought I would find the pics in SMW’s albums... but found nada... no pics at all...

Best regards,

-a-

[larryb]

If the knob spins then the wire is broken at the knob. Take out the pilot seat then the pilot side wall. It is not hard, 2 hours start to finish even the first time. This is the very rare aviation repair where the parts are less than $10.

[Mooney217RN]

Many thanks for the responses & suggestions.  It sounds like the wire is broken at the knob or that it has come loose.  But I am going to look in the rear of the fuselage first as Paul recommended above as the easier means of inspection.

Thank you all again!

[smwash02]

@carusoam thanks for helping clarify that, I didn't think to put the adventure in my albums. I'll do that in the future to make it easier to find.

@Mooney 217RN Hope it's an easy fix for you!

[Mooney217RN]

Problem solved.  O2 System fixed.  Many thanks for all of your good suggestions.

So here's the issue in a nutshell.  We were thinking the plane was going to have to go into Top Gun but there's a problem with transportation getting out of there, so I would've had to stay with the plane.  I was told that if the knob spun without resistance BUT couldn't be pulled off the shaft, the mechanism inside the panel was broken or the cable came loose/off.

The O2 knob had no resistance, but I could not pull it off the shaft.  I did not have the proper allen wrench to check the set screw.  It must be an odd size.  

My closest friend is an IA/A&P in addition to being a retired ATP with ratings in the DC-10 & 757/767.  He has thousands of hours of Mooney time.  He had the correct wrench size, checked the set screw on the knob.  It was loose!  Thank goodness!

You don't want to have to pull that side panel.  It is a major undertaking.

Bottom line - the O2 system is up & running again!

[carusoam]

Great follow-up RN!

Thanks for sharing the detail...

Wonder if somebody went metric at the O2 equipment supplier...

Lately, I have been acquiring more metric tools...

Best regards,

-a-

[Mooney217RN]

I don't know Caruso, I have a full set of allen wrenches, and I couldn't find the size in my selection, so it must be an oddball allen head.