Just when you think you’ve seen it all.

[VA FLYER]

While doing a pre-flight this morning, I noticed that the right MLG tire looked a bit soft. So I cranked it up and taxied over to the maintenance hangar to pump it up. I shut down in front of the hangar and got out. One of the IAs was walking toward me, looking at the ground under my cowling. I followed his gaze and saw the smallest piece shown below, and said “please don’t tell me that came off my airplane.” Sadly, he said “yep, fell out of the spinner when you shut down.”

Bottom line: the spinner bulkhead disintegrated as soon as we removed the spinner. As you might notice, it had apparently been coming apart at radial cracks propagating in at least three places. I’ve been flying since 1967, have owned multiple airplanes over the years, and I’ve never seen this before. 

I don’t know what would happen if the bulkhead came apart at 2500 RPM, but the wonder is that, except for needing air in the tire, I would not have seen this problem. It would at least been a BIG vibration from an unbalanced bulkhead and if that went on long enough, loss of the spinner itself seems possible. Just my lucky day.

Edited August 12, 2022 by VA FLYER

[GeeBee]

Wow, that is the 3rd bulkhead broken of late on this site!

 

[Shadrach]

Until this recent rash of bulkhead incidents, I did not know that so many spinners had a front bulkhead. 

[PT20J]

No idea what model plane or prop you have. The McCauley prop on my M20J needs to have the hub shimmed with teflon tape for a tight fit. Otherwise, the spinner can wobble some.

 

[VA FLYER]

13 minutes ago, PT20J said:

No idea what model plane or prop you have. The McCauley prop on my M20J needs to have the hub shimmed with teflon tape for a tight fit. Otherwise, the spinner can wobble some.

 

It’s a McCauley on an IO-550. There were shims installed but they fell out with the rest of the debris. From the condition of the pieces of the bulkhead, it has been wobbling around for a while. It may be the source of a very faint vibration that would come and go. I flew it with an IA two weeks ago and it, of course, behaved perfectly. After putting the airplane back in the hangar, I found another chunk of the bulkhead right where I initially started the engine to taxi up to maintenance. So the major disintegration began on the start and the shutdown at the maintenance shop five minutes later was the proverbial “last straw”.

[PT20J]

This should be inspected and the shimming adjusted as necessary at every annual inspection.

[Guest]

6 hours ago, PT20J said:

This should be inspected and the shimming adjusted as necessary at every annual inspection.

It should be pretty basic knowledge, with or without the Mooney checklist.

[carusoam]

VA F,

Thanks for the pics and details of your findings!
 

When you get a chance… You can update your avatar data to include what you fly…

A simple note like O1, O2 or O3 can be really helpful… for everyone.

Best regards,

-a-

[carusoam]

What is a that part made of?

Looks like a plastic piece in a pretty stressful environment at 2k+ rpm.

Number of hours it may have seen?

 

Best regards,

-a-

[VA FLYER]

On 8/13/2022 at 12:37 PM, carusoam said:

What is a that part made of?

Looks like a plastic piece in a pretty stressful environment at 2k+ rpm.

Number of hours it may have seen?

 

Best regards,

-a-

Hours on the bulkhead itself unknown for sure, but the prop has about 9 years/650 hours on it. I’d assume the bulkhead was changed at the same time. (Yeah, I know, I know.) It is plastic but it’s a pretty heavy duty plastic. 

[David Lloyd]

Some are a flexible plastic, others are stamped aluminum.  Both need to be properly shimmed.  I've seen cracks in the metal ones but never seen a plastic one come apart.  Both should be inspected for cracks, wear and fit every year.  Bet this one had cracks for a long time before it came apart.

[VA FLYER]

12 hours ago, David Lloyd said:

Some are a flexible plastic, others are stamped aluminum.  Both need to be properly shimmed.  I've seen cracks in the metal ones but never seen a plastic one come apart.  Both should be inspected for cracks, wear and fit every year.  Bet this one had cracks for a long time before it came apart.

Yeah, I think the same. I had the pre buy done as an annual. They probably missed the cracks developing in it. There is considerable fretting on the inner race which suggests to me that the bulkhead failed from repetitive vibrations. I’ve flown it about 70 hours since last November and had recently noticed a mild, rhythmic vibration at about a 10-15 second cycle. Took my local AI for a ride to get hie ideas but it was silky smooth the whole time. I thought I was just getting “new airplane, old pilot” jitters. Maybe the airplane was trying to tell me something and I just didn’t listen close enough.

[VA FLYER]

On 8/12/2022 at 9:35 PM, PT20J said:

This should be inspected and the shimming adjusted as necessary at every annual inspection.

NOW you tell me…

[cbarry]

I’ve often wondered if some of the cracks might  get started by excessive pressure on the out ring area when removed and reinstalled and not just by age and vibration?