Airworthiness Concern Letter 9/24/2024 on legacy Control Yoke

[Yetti]

If this is the passenger yoke, I would also guess getting bumped and grabbed during ingress and egress to the plane has something to do with the stress cracks.    I would have to guess Mooney did not plan for cast aluminum from the mid 1900s to not crack.    Sent this to Jason at the FAA.

 

Jacob,

for the Mooney Control Wheel ACS I noticed it covered all the F models.    The later F models I have a 75 F do not use that kind of control wheel.   Those are the "slim"

Wheel which are on earlier models.

 

Mine has the "mongo" control wheels More like on a J model

 

This is from the Parts Manual #105   

 

 

 

 

 

 

The "mongo" control wheel have different design for the Control Shaft interface.   The interface hole sits more in the body of the yoke so there is more material to support the control shaft.

 

I noticed in the ACS picture the set screw threaded hole was starting to crack around it.    Someone has put way too much torque on this poor wheel.

 

[Yetti]

I think also that is a smaller diameter shaft than in the later model Fs.

[bonal]

My 64D yoke looks a lot different than the one pictured.  Will be discussing this with my IA as I recall him mentioning that I don’t have inspection requirement.  Of course could just be wishful thinking on my part (no pun intended). Since there is still a Mooney corporation making parts would this issue be sufficient for them to begin manufacturing a replacement yoke as there would be hundreds if not thousands needed. Using a newer model design and if needed a sleeve for proper fitting.  Sadly from a motorcycle or automotive aftermarket perspective this should be a big nothing burger.  I guess we will all have to see how this plays out.

[Grant_Waite]

4 hours ago, AJ88V said:

One issue is that any crack is potentially hidden under the plastic (powdercoat?) finish which is flaking on mine (looks like a crack, but evidently metal underneath is good).

I talked to my A&P about this and specifically asked if we could adapt with this nice, machined billet ACS yoke

(https://www.aircraftspruce.com/catalog/appages/acscontrolwhl3b.php?clickkey=7575)

That got a hearty NO response.  So it's ok to spend $750 for a 50 year old used part made of cast metal that is known to crack, but we can't substitute a modern part like the ACS which is both stronger and cheaper.

When I called Cygnet early this year, they told me that Mooney was supposedly sending them drawings for yokes. Maybe eventually they will make replacement, modern Mooney yokes. I’ve seen a Mooney with cygnet yokes and it looked quite nice. It’s all who you get to do the work. You could ask around and I’m sure you could find someone who’d install a cygnet yoke in a Mooney. 

[bonal]

Just looked on aircraft spruce and they have an ACS yoke machined from 6061 T6 billet for 139 dollars.  Certified requirements prevent us from using a perfectly suitable part as a replacement for something that isn’t as good.

[bonal]

Oops sorry it’s 136 dollars 

[AJ88V]

1 hour ago, Shadrach said:

I will have to verify the next time I’m at the hanger, but I do not believe that my yolk “rocks“ on the shaft

The copilot yoke on my 1970C looks exactly like the broken one.  IA said he inspected the yokes there were no cracks during the shaft inspection.  My yokes DO rock slightly, which is another reason why I was looking at those ACS yokes on Aircraft Spruce.

[AJ88V]

Just posting Mooney SBM20-205B control shaft inspection for reference

https://www.mooney.com/wp-content/uploads/2020/12/SBM20-205B.pdf

It does not specify inspection of the control yokes as noted int the Airworthiness Concern.

[N204TA]

2 hours ago, Shadrach said:

That is an ugly and catastrophic failure for sure. However, if I’m honest, I think the design and construction of the old welded shaft is superior to the new drilled and bolted version. The new design is definitely less expensive to produce though.

The worst part of the new design is that it’s nearly impossible to feed wires through the inside of the shaft.  I managed to get the PC vacuum hose and the wires for the post light above the clock in there, but there wasn’t room for the PTT and electric trim wires so I had to get creative.

[Shadrach]

17 minutes ago, N204TA said:

The worst part of the new design is that it’s nearly impossible to feed wires through the inside of the shaft.  I managed to get the PC vacuum hose and the wires for the post light above the clock in there, but there wasn’t room for the PTT and electric trim wires so I had to get creative.

That sucks. Surely Mooney is running PTT, trim and AP disconnect switches through the shaft.

[Skates97]

2 hours ago, Yetti said:

I think also that is a smaller diameter shaft than in the later model Fs.

The OD of the shafts are all the same, the later models that don't have the AD had a thicker material for the shaft resulting in a smaller ID.  The older M20's were 0.04 thickness and the newer M20's are 0.06.

[Hank]

3 minutes ago, Skates97 said:

The OD of the shafts are all the same, the later models that don't have the AD had a thicker material for the shaft resulting in a smaller ID.  The older M20's were 0.04 thickness and the newer M20's are 0.06.

That's a reduction of 0.040" / 1.0 mm in the indpside diameter of the shaft.

23 minutes ago, N204TA said:

The worst part of the new design is that it’s nearly impossible to feed wires through the inside of the shaft.  I managed to get the PC vacuum hose and the wires for the post light above the clock in there, but there wasn’t room for the PTT and electric trim wires so I had to get creative.

How fat are all of these cables? Surely a 1mm smaller shaft wouldn't eliminate all of those wires?

[N204TA]

4 minutes ago, Hank said:

How fat are all of these cables? Surely a 1mm smaller shaft wouldn't eliminate all of those wires?

The diameter of the shaft itself isn’t the problem, it’s how it’s attached to the bracket for the linkages.  The old one was welded into a cradle leaving a hollow shaft with lots of space between the end of the shaft and the vertical bracket to feed the wires.  With the new one, the shaft is inserted into a sleeve not only leaving very little room at the end to get wires in there, but then you have to squeeze around the two crossing rivets.

[Hank]

20 minutes ago, N204TA said:

The diameter of the shaft itself isn’t the problem, it’s how it’s attached to the bracket for the linkages.  The old one was welded into a cradle leaving a hollow shaft with lots of space between the end of the shaft and the vertical bracket to feed the wires.  With the new one, the shaft is inserted into a sleeve not only leaving very little room at the end to get wires in there, but then you have to squeeze around the two crossing rivets.

Ah so ka. That picture is worth a couple thousand words. It would be tedious trying to fish many wires around those rivets with such little space above it.

Do you think pushing a piece of thin piano wire through from the other end, then taping the wires to it and pulling them down would be any easier? It would need to be thin enough to flex out around the linkage.

[Hector]

When I called Cygnet early this year, they told me that Mooney was supposedly sending them drawings for yokes. Maybe eventually they will make replacement, modern Mooney yokes. I’ve seen a Mooney with cygnet yokes and it looked quite nice. It’s all who you get to do the work. You could ask around and I’m sure you could find someone who’d install a cygnet yoke in a Mooney. 

When I purchased my F last December it came with the cygnet yokes. I have to say, I love them! No tapered pin. An AN bolt thru the yoke and shaft.


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[Grant_Waite]

52 minutes ago, Hector said:

When I purchased my F last December it came with the cygnet yokes. I have to say, I love them! No tapered pin. An AN bolt thru the yoke and shaft.


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Man they look even better than I remembered them. I’m not a fan of the ram horns. But I do like the newest Mooney yokes. But the cygnets won’t break the bank. Just missing a leather wrap ;)

[Hank]

4 minutes ago, Grant_Waite said:

Man they look even better than I remembered them. I’m not a fan of the ram horns. But I do like the newest Mooney yokes. But the cygnets won’t break the bank. Just missing a leather wrap

Leather wrap is easier to add than a yoke clock. I'm hooked on mine! Use it every flight. 

[FlyingDude]

If I'm not wrong, the new style yoke shafts are 2" longer, further pushing the already bigger yoke into your stomach. I don't understand why one cannot strengthen the old yoke shafts by sticking a longer rod inside of them and then rosette welding them, instead of using a 2" insert held by AN bolt. 

I'm fit, no tummy, yet the cabin is crammed. Especially for the front pax when rear seats are occupied. 

 

Edit. Wrote to Mooney. 

[FlyingDude]

I just realized the manual 203 dated 1976 covers my plane and the shaft pn are 720005-1 whereas the sb20-205 addresses 710005- numbers. What am I missing?

[47U]

1 hour ago, FlyingDude said:

What am I missing?

My best guess?  It’s a typo.  Your yoke shafts should be pn 710005-1/-2.

Fig 29, Ind 1 (pg 120) shows 720005-501 as the rudder torque tube assy (in front of the rudder pedals).

 

Further, the part number/page cross reference shows 710005-000 on page 114, which is where the yoke shafts are depicted.

[cliffy]

On 9/26/2024 at 9:31 AM, AJ88V said:

That got a hearty NO response.  So it's ok to spend $750 for a 50 year old used part made of cast metal that is known to crack, but we can't substitute a modern part like the ACS which is both stronger and cheaper.

And as Walter Cronkite used to say- "That's the way it is"

 I'm of the opinion that it comes from over tightening the taper pin every 500 hrs, on a cast part. 

Like mentioned above my 64 has an AN bolt through it and has never shown a crack on dye check. 

As to "making or using non-approved parts"?  Anyone ever hear of "Primary Category" ?

[DCarlton]

On 9/26/2024 at 12:34 PM, Shadrach said:

I will have to verify the next time I’m at the hanger, but I do not believe that my yolk “rocks“ on the shaft

If my set screw is not tight, it will move a little side to side on the shaft.  Always has.  That tells me if you tighten down the set screw, there's a significant point load at the screw.  I'll bet many are that way; otherwise it would be hard to get the yoke on and off the shaft.  I think.. I'm no expert.