Mooney Elevator AD

[Flyman2456]

On 3/24/2023 at 4:53 PM, Kelpro999 said:

Soo…. the arm remains the same and the weight increased by one pound yet balance is still ok. Raises the question that if adding a pound some time in the past would have been ok? Were they always overly unbalanced that much?

Sorry, old unbalance was 20-22in-lbs. New unbalance with the new weights is within the SB spec, 14-16.75inch-lbs

[carusoam]

Sounds like we could use a factory rep to cover some of the issues/questions with the counterweights here?

Let’s invite @Jonny

Getting this done correctly is important for everyone, including the factory.

Best regards,

-a-

[Gary0747]

11 hours ago, carusoam said:

Sounds like we could use a factory rep to cover some of the issues/questions with the counterweights here?

The new weights come right in spec with the service bulletin without filing so that worked perfect.  The only issue I see is did the mechanic install rivets too short for the specific elevator he worked on.  As mentioned above DMax has longer ones that can be cut to the proper length for a good set.  

[Flyman2456]

On 3/24/2023 at 12:45 PM, Kelpro999 said:

If that’s new rivets then they are completely wrong. I had what would have been same problem balancing mine. Mooney p/n rivets were so short no attempt was made. Buying longer than needed allowed cutting down during practice / testing until proper fit obtained. If those are new struck rivets, removing may be problematic for same reason claimed. At this point welding to the flat head and pulling may be the better way. Creativity will get them out. Striking stuck fat rivets usually makes them fatter.

 Photo of rivets I started with before cutting.

Did you coat them with anything before installing? The ones in the kit are painted

[Kelpro999]

3 hours ago, Flyman2456 said:

Did you coat them with anything before installing? The ones in the kit are painted

Sprayed with zinc phosphate. Probably not necessary since the original had nothing, even the weights were bare but before installing I also used zinc phosphate. 
 Are you replacing weights as part of the AD? I’m wondering if there is a revision to the service manual for new balance specifications besides the service bulletin? Also adding two pounds to the tail is like eight to the hat shelf. 
 This whole AD has created more questions than solutions so proceed with caution. 
Just my two cents 

[Flyman2456]

On 4/12/2023 at 4:37 PM, Kelpro999 said:

Sprayed with zinc phosphate. Probably not necessary since the original had nothing, even the weights were bare but before installing I also used zinc phosphate. 
 Are you replacing weights as part of the AD? I’m wondering if there is a revision to the service manual for new balance specifications besides the service bulletin? Also adding two pounds to the tail is like eight to the hat shelf. 
 This whole AD has created more questions than solutions so proceed with caution. 
Just my two cents 

Yes replacing them as part of the AD. He was able to install the iron rivets using the longer ones from Don. He said it helped to heat them up and then install with a big rivet gun. 

[Kelpro999]

1 hour ago, Flyman2456 said:

Yes replacing them as part of the AD. He was able to install the iron rivets using the longer ones from Don. He said it helped to heat them up and then install with a big rivet gun. 

Good job.
 I’m still wondering about the changes to balance issues but I guess it’s not a problem or at least haven’t heard of it yet. Have you flown it yet? Preferably nose down 5deg. WOT @2350rpm.  No..just kidding  but eventually someone will test it.

[EricJ]

56 minutes ago, Kelpro999 said:

Good job.
 I’m still wondering about the changes to balance issues but I guess it’s not a problem or at least haven’t heard of it yet. Have you flown it yet? Preferably nose down 5deg. WOT @2350rpm.  No..just kidding  but eventually someone will test it.

The balance change is consistent with the mass of the new weights and matches the balance specs for the other models (or s/ns) using the same balance weights. 

[Kelpro999]

2 hours ago, EricJ said:

The balance change is consistent with the mass of the new weights and matches the balance specs for the other models (or s/ns) using the same balance weights. 

 If the same elevator was within balance specification limits listed in the service manual before weight change, is it still within  limits in the same service manual after the weight change? Was a revision to the manual made?

 I was under the impression that maintaining specific balance limits was important for aerodynamic reasons based on shape & elasticity more than anything else. Now I see it seems to have been an arbitrary number based on what weight dimension fit into the horn at the time. Now the question is… why remove elevators when replacing weights when balance target is arbitrary? If the new weights weigh 3.2lbs then the “new” specifications will be met without question.

[EricJ]

2 minutes ago, Kelpro999 said:

 If the same elevator was within balance specification limits listed in the service manual before weight change, is it still within  limits in the same service manual after the weight change? Was a revision to the manual made?

 I was under the impression that maintaining specific balance limits was important for aerodynamic reasons based on shape & elasticity more than anything else. Now I see it seems to have been an arbitrary number based on what weight dimension fit into the horn at the time. Now the question is… why remove elevators when replacing weights when balance target is arbitrary? If the new weights weigh 3.2lbs then the “new” specifications will be met without question.

There are before and after balance specs in the AD.    The "before" specs are consistent with the hybrid weights, and the "after" specs are consistent with the heavier replacement balance weights.   The "after" specs match models and s/ns that originally had those weights.

Having two separate balance specs in the AD was confusing until we did one of these, and then it made sense.

[Kelpro999]

2 minutes ago, EricJ said:

There are before and after balance specs in the AD.    The "before" specs are consistent with the hybrid weights, and the "after" specs are consistent with the heavier replacement balance weights.   The "after" specs match models and s/ns that originally had those weights.

Having two separate balance specs in the AD was confusing until we did one of these, and then it made sense.

 Sounds like any elevator with non-hybrid weights would still work fine if someone sawed a pound off each one. Now the question remains.. why remove the elevators for a simple part replacement 

[EricJ]

3 minutes ago, Kelpro999 said:

Now the question remains.. why remove the elevators for a simple part replacement 

To verify that it meets the balance specs with the new weights.

[Flyman2456]

After months of being down waiting for parts, the replacement is complete. Very frustrating to have incorrectly sized rivets in the parts kit. The iron rivets also made it difficult. The elevators statically balanced perfectly within the new balance specs with the new weights. Flew the plane and no noticeable difference in flight controls. 

[Robert67]

I was a little unclear on the new weights since they are quite a bit heavier than the old ones.   Here is a message I sent Frank Crawford and his response.  Helps to clarify the issue  

Hi Mr. Crawford

I am in receipt of the elevator weight replacement kit for my 1967 M20F serial# 670102. The new replacement weights are significantly heavier than the old weights.  The balance range in my 1967 service manual allows for a maximum static unbalance force of 1.725 lbs.  However service bulletin M20-345A allows for a maximum static unbalance force of 1.30 lbs.  I would like to confirm that I am safe to balance the new weight to the balance limits in the service bulletin and Not to the balance limits in the 1967 service manual before I perform the installation of the new weights.  Please advise.

Hello Robert,

The Service Bulletin does indicate that the Weight is to be balanced per the Service Bulletin M20-345A – The 1967 Manual (Do Not use the Data from the current 1967 S&M) this only shows balancing information for the Hybrid weight 430018. The Service Manual will need to be updated to show this (I do not have a time table as of yet), but until that time, the balancing data is shown on page 3 and 4 of the Service Bulletin M20-345A.