Factory Response- M20 Empennage Issue

[sellis]

Dear Mooney Owners,

 

Nothing is more frustrating than being greeted with a nasty Service Bulletin, and have no history behind it. Therefore, here’s the rationale behind the required inspection:

In late January, I received a report from an Acclaim owner in Poland that they had experienced a separation of the Empennage hinge assembly from the Empennage bulkhead. It happened shortly after takeoff. The pilot reported that at about 200’ AGL, he encountered some magnitude of vertical shear, heard a loud bang in the tail, and the aircraft pitched nose up. With the assistance of another pilot in the right seat, the two of them managed to push the nose down enough, with throttle control, to land the airplane safely. My hat is off to these two pilots to say the least. Upon examination, it was found that the rear hinge, filler plate, and Jack screw lug had pulled apart from the Empennage bulkhead, Huck pins and all. The collars were found inside the stinger. I had the hardware shipped to me for investigation. I had pictures of the empennage sent too. The pictures revealed that the filler plate had been installed on the wrong side of the hinge. In the correct stack up, the hinge has a .032” surface milled above the hinge pivot. The hinge is then installed with a .040” filler plate that sits between the hinge and the bulkhead. The purpose here is twofold: One, it holds the hinge pivot off the bulkhead .008” to allow rotation of the hinge plate without galling the bulkhead. Second, it keeps the hinge parallel to the bulkhead, minimizing shear forces on the Huck pin. Our working theory was that without the filler plate between the hinge and bulkhead, the installed pins would not pull up perpendicular to the bulkhead, and the collars would not swedge properly. Also, with the .040” filler still in the stack, there was now an added .032” gap added to the lower row of Hucks, changing the grip length. Our theory was that this had allowed the hinge to “work” on the bulkhead, thereby allowing the Huck pins to loosen in their holes. Add a vertical gust load, and the lower Huck pins and collars would have failed first, then pulling the upper pins loose due to the lever action.

This was done in conjunction with FAA Engineers, whom I contacted immediately after receiving the hardware and pictures from Poland and determining there was more to this than wind shear. I am required (and would do it anyway, ask anyone who knows me) to report a failure such as this to the FAA within 24 hours of determining that the failure was one that is covered by FAR 21.3.

Mooney and FAA agreed that an AD should be issued, and due to the failure mode, it should be an immediate Emergency AD based on our Service Bulletin M20-313. With that accomplished, it was discovered that the next sequential S/N produced after the Polish airplane was incorrect also. Service Bulletin M20-314 was issued to put the airplane(s) back to Type Design. This new result was not like the previous, as there were no signs of movement in the assembly, it was just put together improperly. The only common factor we could find was that the same assembler has assembled both tails on the same day, and the same inspector had signed off on the installation. So we set the effectivity at the beginning of this installer’s tenure in the Empennage shop, and went back from there 10 airframes, just to be sure. We also made test coupons and tested our Huck guns for proper pull and swedging. All passed.

Weeks went by, and the Confirmation cards flooded in. All were reported inspected and proper, with good collar swedges on the Huck collars. I was starting to thing we had caught the only two, when another TN was reported to be found incorrect. This one was built by the same assembler, exactly one year to the day before the original two were produced. I have no idea what that tells us, but the confident feeling was leaving me. Two days later, an Eagle eyed mechanic at one of our Service Center’s called me to tell me that he was doing an Annual on a 1990 J Model, and thought he’d just take a look at the hinge. It was incorrect. This airplane had 1400 hours on it. I visited the airplane, and found no movement of the hinge, and good Huck bolt installations. My feeling is that it would have flown forever in that condition, no problems. However, it wasn’t right, it wasn’t to Type Design, and it had to be corrected. So, yet another call was made to FAA, their Engineers came out again, and we now had to try to isolate an effectivity once again. Inspection records from 1990 showed that another assembler had built the J Model’s tail. That means we had lost the common denominator used to set the original effectivity. Next stop was the Stinger assembly drawing to see if there was a change in construction in the past that would allow us to point at a specific time when we knew that all was well. Turns out that the hinge mounting hasn’t changed since 1961, with the introduction of the M20B.

This is where my job gets hard. We have nothing to correlate the improper assembly to. We still do not know the root cause of the failure in Poland, or why the others that have been identified have not loosened up like that one did. I have nothing that I can set an effectivity to after the initial design that is in use today. Therefore, I have decided that ALL airframes need to be looked at. The design is better than good, calculated to withstand 10 times ultimate load, and actually tested to 1.8 timed positive and negative gust Ultimate load. There has NEVER been a reported failure of this assembly, until the one in Poland. Even that one was flown to a safe landing. The chatter about the Empennage falling off is incorrect. The primary attach points are the Empennage pivot point and the elevator control rods. The hinge’s primary job is to allow for longitudinal trim, and to stabilize the Empennage laterally.

I have had to do this before. But I did it without hesitation, because it was the right thing to do.

Inspecting your airplanes is also the right thing to do. We absolutely have to know that this issue does not exist anywhere else. YOU absolutely have to know that this issue does not exist anywhere else. It’s going to cost you an hour of labor to have that peace of mind. You may curse me for making you do it. But at least you’ll be around to curse me, and that’s what matters most to all of us here at Mooney.

 

 Bill Eldred

Director of Engineering

Mooney Aviation Company, Inc. 

165 Al Mooney Drive North

Kerrville, TX. 78028

Direct Email: beldred@mooney.com
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[orangemtl]

Thank you for the comprehensive explanation. My aircraft (31-0036) was inspected and cleared. Good to know not that the vast majority were fine, but that others were found and corrected.

We all understand the fanatical level of detail necessary in issuing ADs, and the necessary 'overkill' that results. Such is the nature of imerfect human beings, flying heavier-than-air machinery, assembled by other imperfect humans, and maintained by same.

[MooneyMitch]

Thank you Stacey and Bill.  I know everyone will sincerely appreciate this level of communication from Mooney.

[David Mazer]

Thank you for standing up and helping us take care of ourselves and our airplanes.  Mine will be inspected soon.

[Cris]

While I understand that the original SB M20 313 was turned into an emergency AD is this new SB 313 A a service bulletin (optional) or an AD?  In any event I will have it looked at but I am curious. Thanks 

[Ned Gravel]

Well done Stacey and Bill.  Doing the right thing is not about being popular. 

If this effort saves only one life, it is worth every hour's cost to inspect every Mooney still flying.

[gsengle]

THANKS Stacey and Bill!  A communication like this is great.  My Ovation, 1996 serial number 89, was just inspected and was fine.  I hope we will start seeing new Mooneys one day soon.

[Cris]

I thought I'd bump this back to the top. I still would like to know if this SB which started for the R & M is now an AD for all models of Mooney's?

[Bennett]

Took N335BB (M20J) to LASAR last week.  All is well, and I feel better for knowing that.  

[231Pilot]

Mine was checked last week and is OK.  Thanks for working to keep us safe.

[OR75]

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/Frameset?OpenPage

Only for the R and TN models so far it looks like. Issuing an AD is a process.

Easy enough to remove the fairing and look in the meantime.

 

[Cris]

Quote: OR75

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/Frameset?OpenPage

Only for the R and TN models so far it looks like. Issuing an AD is a process.

Easy enough to remove the fairing and look in the meantime.

 

[1964-M20E]

OK just to make sure I get this correct.  Service Bulletin M20-313A is done first and if everything is correct SB-M20314A does not apply.  I just downloaded the SBs and reviewing them so that my mechanic and I can take care of this by the end of this week.

[Urs_Wildermuth]

Ok, do I understand this correctly that there will be an AD for ALL Mooneys from the B- up to the very last built?

[OR75]

ADs are issued by the FAA (and no one else) following a process. 

I would say that even if you comply with the SB now, once the AD is published, you will still need to visit with your favorite A&P for him to make a log book entry that the AD has been complied with once and if it is  indeed issued by the FAA.

AD = mandatory and need log book entry

SB = not mandatory  (for most of the pleasure flying most of us on here do)

 

[pjsny78]

I just went to don maxwells last week to get this SB checkout out. He informed me both on my log book entry and verbally that this is a SB now but in a few days will be issued as a AD for all mooney models. This was last week so if it is not a AD now it will be very soon.

[John Pleisse]

Quote: pjsny78

I just went to don maxwells last week to get this SB checkout out. He informed me both on my log book entry and verbally that this is a SB now but in a few days will be issued as a AD for all mooney models. This was last week so if it is not a AD now it will be very soon.

[pjsny78]

why does no one beleive me?

[Sabremech]

It's more likely to reference S/B M20-313A compliance as meeting the requirements of the AD. No need to go back to your A&P for a sign off if already done with the S/B. As the owner, you can note this in your logbook. When and if the AD comes out, it will state this in the compliance section. 

[sellis]

It will be an AD. The FAA is in the process of revising the current AD and should release it any day now and it will reference M20-313.

[bnicolette]

My annual was just completed and had the SB313A signed off.  My mechanic told me that the AD will be considered complied with when it comes out and no further action will be necessary.

 

[Urs_Wildermuth]

So what can we with C models and other not jet referenced models do? Wait to be grounded and then act or can we do this inspection beforehand?

[Ned Gravel]

Mine is now done too.  When I read pjsny's comment, I called Clarence and he told me it had been done the previous day. 

[Urs_Wildermuth]

ok, mine is getting done tomorrow.

[rbridges]

I'm new to this.  I sent an email to my IA.  Does the FAA send you written notice when an AD is created?