Mooney Elevator AD

[Gary0747]

The new -7 weights are supposed to be between 3.0 and 3.5 pounds when installed.  Does anybody know the weight of the old -1 hybrid weights?

[A64Pilot]

On 2/17/2023 at 6:22 PM, Gary0747 said:

The new -7 weights are supposed to be between 3.0 and 3.5 pounds when installed.  Does anybody know the weight of the old -1 hybrid weights?

Weight shouldn’t change unless the balance does, and I don’t think it does

[A64Pilot]

On 2/8/2023 at 10:30 AM, Gary0747 said:

I know this is true for high speed aircraft but Is this true for GA aircraft flying at normal speeds?    I can’t recall reading an accident report on any GA aircraft where flutter was mentioned as the cause?  Yes GA aircraft have lost tails when accidentally penetrating thunderstorms or conducting abrupt control movements but the cause there has been exceeding the g force limits of the aircraft design.  

Good friend of mine, my Civilian test pilot mentor. This was an Experimental airplane at the time, but had been tested to ensure it wouldn’t flutter etc and was within balance, Rockwell later duplicated the event in a wind tunnel and time between onset of flutter and complete disintegration of the empennage was less than 1 sec. Ralph barely got out, the Flutter Engineer flying with him didn’t. The crash did trip a design change

https://aviation-safety.net/wikibase/2731

The Piper video is a little misleading as it is very low frequency flutter and gives the impression that you have time to slow down, sometimes you do, and sometimes you don’t.

Flutter to me is terrifying, I used to fly a lot of RC, and sometimes you would see something come off the aircraft and then hear a paper tearing sound, that was the flight control being torn off from flutter, the thought of that occurring in a real aircraft is scary.

[Kelpro999]

On 2/17/2023 at 3:22 PM, Gary0747 said:

The new -7 weights are supposed to be between 3.0 and 3.5 pounds when installed.  Does anybody know the weight of the old -1 hybrid weights?

Good question, this is an old non-hybrid after adding 5oz.

[Gary0747]

2 hours ago, A64Pilot said:

Weight shouldn’t change unless the balance does, and I don’t think it does

This is what I was thinking also but was wondering if the new -7 weights were close enough in weight to file them for proper balance.

this is from the SBM20-345A

“The 430018-1 balance weight is similar in size and shape (but not in weight) to the 430016-7 balance weight.”

[Kelpro999]

22 hours ago, Gary0747 said:

This is what I was thinking also but was wondering if the new -7 weights were close enough in weight to file them for proper balance.

this is from the SBM20-345A

“The 430018-1 balance weight is similar in size and shape (but not in weight) to the 430016-7 balance weight.”

The -1 are said to be lighter than-7 and that makes sense given same dimension using lead instead of steel in some of it.  If you were “in” balance with hybrids you may need to file your new ones.

Edited February 21, 2023 by Kelpro999
Dyslexic mind

[Gary0747]

39 minutes ago, Kelpro999 said:

The -1 are said to be heavier than-7 and that makes sense given same dimension using lead instead of steel in some of it.  If you were “in” balance with hybrids you may need to file your new ones.

What I was worried about is the lower weight limit allowed in the SB of 3.0 pounds   The hybrids are no doubt lighter and they may well be less than that 3.0 pound lower limit.  The early smooth skin elevators had a significantly higher unbalance weight specification than the later Ribed skin elevators.  So that also points to needing lighter weights for the smooth skinned elevators.   I can not find any weight limits in any of the early service manuals and it is not clear where they come from in the SB? 

[Kelpro999]

1 hour ago, Gary0747 said:

What I was worried about is the lower weight limit allowed in the SB of 3.0 pounds   The hybrids are no doubt lighter and they may well be less than that 3.0 pound lower limit.  The early smooth skin elevators had a significantly higher unbalance weight specification than the later Ribed skin elevators.  So that also points to needing lighter weights for the smooth skinned elevators.   I can not find any weight limits in any of the early service manuals and it is not clear where they come from in the SB? 

Early service manuals aren’t very “complete”.  Contact Frank at support@mooney.com for more detailed information given your serial number. That’s where I get it.

[Igor_U]

On 2/17/2023 at 3:22 PM, Gary0747 said:

The new -7 weights are supposed to be between 3.0 and 3.5 pounds when installed.  Does anybody know the weight of the old -1 hybrid weights?

I measured the -1 weight and it was 2.1lb. The -7 weight it replaced is 3.28 lb and predictably the whole elevator was in balance with it. Actual value was 1.22lb (limits were 1.09-1.3). It makes sense as more weight in front (counterweight) reduces the balance weight at the TE.

Or maybe I was lucky? 

[Kelpro999]

27 minutes ago, Igor_U said:

I measured the -1 weight and it was 2.1lb. The -7 weight it replaced is 3.28 lb and predictably the whole elevator was in balance with it. Actual value was 1.22lb (limits were 1.09-1.3). It makes sense as more weight in front (counterweight) reduces the balance weight at the TE.

Or maybe I was lucky? 

  Was it flying good with the-1? What was the before unbalance measurements? Now it has the new-7 yet balance is within range?

 Feeling confused 

[Gary0747]

1 hour ago, Igor_U said:

I measured the -1 weight and it was 2.1lb. The -7 weight it replaced is 3.28 lb and predictably the whole elevator was in balance with it. Actual value was 1.22lb (limits were 1.09-1.3). It makes sense as more weight in front (counterweight) reduces the balance weight at the TE.

I can not figure how the SB changes the original service manual unbalance requirements of 1.57 to 1.725 pounds?  For the smooth skin pre 1968 M20F?  Did they go test fly VNE to test for flutter or was it a calculation?  The numbers you are quoting and using 1.09 to 1.3 pounds happen to be for all the post 1968 M20F and 201 aircraft which have ribbed elevators not smooth.    Is this a mistake?

And what about all the pre SB elevator rebalancing with smooth weights or repainting?  Which balance number did they use since presumably only the service manual was the only reference.   I brought this up before but apparently no one has an answer   

[Kelpro999]

48 minutes ago, Gary0747 said:

I can not figure how the SB changes the original service manual unbalance requirements of 1.57 to 1.725 pounds?  For the smooth skin pre 1968 M20F?  Did they go test fly VNE to test for flutter or was it a calculation?  The numbers you are quoting and using 1.09 to 1.3 pounds happen to be for all the post 1968 M20F and 201 aircraft which have ribbed elevators not smooth.    Is this a mistake?

And what about all the pre SB elevator rebalancing with smooth weights or repainting?  Which balance number did they use since presumably only the service manual was the only reference.   I brought this up before but apparently no one has an answer   

I see the SB change specs between steps 4.1 and 2.12 

[Gary0747]

13 minutes ago, Kelpro999 said:

I see the SB change specs between steps 4.1 and 2.12 

Yes step 2 is for the case the current hybrid -1 weight passes the stripping and 10x magnifier test and the owner wants to continue pulling the elevator off for an annual re-inspection.   (No one will want to do this.)  Step 4 is replacement of the hybrid -1 weight with a new solid -7 weight.   The early M20Fs before 1968 (540 in this category) had both -1 and -7 weights since there were only about 130 hybrid weight sets installed.  
Does anybody know for sure when the transition from smooth to ribbed elevators occurred?  I am assuming 1968 but am not sure?   I hope the original test flight data still exists?  

[Kelpro999]

13 minutes ago, Gary0747 said:

Yes step 2 is for the case the current hybrid -1 weight passes the stripping and 10x magnifier test and the owner wants to continue pulling the elevator off for an annual re-inspection.   (No one will want to do this.)  Step 4 is replacement of the hybrid -1 weight with a new solid -7 weight.   The early M20Fs before 1968 (540 in this category) had both -1 and -7 weights since there were only about 130 hybrid weight sets installed.  
Does anybody know for sure when the transition from smooth to ribbed elevators occurred?  I am assuming 1968 but am not sure?   I hope the original test flight data still exists?  

Not understanding the relevance of ribbed elevators since they’re not part of the AD nor SB but I do see a large unbalance spec change with only a 1% arm length change between the two steps in the SB.

[Gary0747]

8 minutes ago, Kelpro999 said:

Not understanding the relevance of ribbed elevators since they’re not part of the AD nor SB but I do see a large unbalance spec change with only a 1% arm length change between the two steps in the SB.

Yes Ribbed elevators should not be part of the AD unless somebody switched weights.  The AD primarily affects the smooth skinned early M20F.  The issue is why is the AD using unbalance weights for the ribbed elevator instead of the unbalanced weight for the earlier smooth skinned elevator?  Perhaps they have flutter test data that says there is no difference but this is contrary to the original service manual numbers?  

[Kelpro999]

2 minutes ago, Gary0747 said:

Yes Ribbed elevators should not be part of the AD unless somebody switched weights.  The AD primarily affects the smooth skinned early M20F.  The issue is why is the AD using unbalance weights for the ribbed elevator instead of the unbalanced weight for the earlier smooth skinned elevator?  Perhaps they have flutter test data that says there is no difference but this is contrary to the original service manual numbers?  

Oh.. I was unaware the -1 / -7 weights would even fit into the ribbed elevator arm. I haven’t paid attention to the ribbed design. 

[Gary0747]

Looking at the type certificate for the M20F the rigging of the elevator is different for the pre 1968 models compared to those made after so it seems a stretch to say they are all the same.

 

“(for Aircraft with Serial Nos. to 680001): With stabilizer set at 31⁄2° negative setting to the thrust line, adjust trim assist unit 740128 for elevator up angle of 5° +⁄− 1° at the zero spring travel position.
(for Aircraft with Serial Nos. 680001 and up): With stabilizer set at 3° negative setting to the thrust line, adjust trim assist bungees 740188 for elevator position of 19° +⁄− 1° at the zero spring travel position of the bungees. (This rigging to be obtained before installation of the 740171 extension springs).”
 

 

[A64Pilot]

14 hours ago, Gary0747 said:

   I hope the original test flight data still exists?  

Flight test is pass / fail, it didn’t flutter as it’s Certified so it passed, but other than that the the VD test flight doesn’t have any data.

The actual test that gives data is called a “Ground Vibration Test” which is done of course on the ground in a building, the aircraft is shaken and has accelerometers installed in the airframe and they are looking for harmonics at certain frequencies that apparently correspond to air speeds. Ballasting a flight control changes it’s harmonic frequency, the more weight in the nose of the control moves it’s flutter to higher air speeds, but there are other considerations of course, like the flight control system adds mass to the system and aerodynamic’s like trim tabs etc. An excessively worn / loose trim tab can aggravate flutter etc.

I can only speak to the S2R-H80 and on it the flutter margin was over twice VNE, and think flutter margins are usually rather big, but once in a Blue Moon the test is wrong or there are other issues that could cause flutter so a test flight is required to validate the test. The link I posted to N112AC accident was one of those, the aircraft was good for GVT but it had only one trim tab one one elevator and that along with the test pilot had trimmed full nose down for the dive test started flutter and disentigrated the tail pretty much instantly.

It was actually a control doublet that initiated the flutter, but without an asymmetric load from one trim tab, and it being full down there would have been no flutter, so it took all three conditions to flutter.

The design was changed to a trim tab on each elevator.

Anytime I rebalance a flight control I do so, so it’s tail light but within specs of course, reason is any paint or repair or whatever adds weight to the trailing edge and if you start light you might still be within limits after the paint or repair or whatever.

[Igor_U]

17 hours ago, Kelpro999 said:

  Was it flying good with the-1? What was the before unbalance measurements? Now it has the new-7 yet balance is within range?

 Feeling confused 

oh, too many questions... 

it flew well with -1 weight. Unfortunately I didn't measure the elevator with the old weight; I simply forgot. I understand the confusion and perhaps you might want to contact Frank Crawford at Mooney if he has answers. He was adamant that was correct.

Please keep in mind that 1967 F unbalance limit was 1.57 -1.725 but the early 68F (up to S/n 170 or ) has same smooth elevator but solid  weight (-7) however unbalance is specified as 1.09-1.3lb so Mooney must have some data. This is with smooth elevators.

so, how did it balance in the range? Lucky I guess but it makes sense as heavier Wight in front will give you lower unbalance value at the elevator trailing edge. 

 

 

[Gary0747]

1 hour ago, Igor_U said:

oh, too many questions... 

it flew well with -1 weight. Unfortunately I didn't measure the elevator with the old weight; I simply forgot. I understand the confusion and perhaps you might want to contact Frank Crawford at Mooney if he has answers. He was adamant that was correct.

Please keep in mind that 1967 F unbalance limit was 1.57 -1.725 but the early 68F (up to S/n 170 or ) has same smooth elevator but solid  weight (-7) however unbalance is specified as 1.09-1.3lb so Mooney must have some data. This is with smooth elevators.

so, how did it balance in the range? Lucky I guess but it makes sense as heavier Wight in front will give you lower unbalance value at the elevator trailing edge. 

 

 

I measured my elevator when it came off and the weight was 1.60 pounds to 1.62 pounds. So now I am being told these numbers are not correct even though they are correct according to my service manual that applied to the first 540 M20F?  The parts catalog only lists the -1 hybrid weight not the -7. So the question is which one was tested with the smooth elevators?   

[Kelpro999]

4 minutes ago, Gary0747 said:

I measured my elevator when it came off and the weight was 1.60 pounds to 1.62 pounds. So now I am being told these numbers are not correct even though they are correct according to my with my service manual that applied to the first 540 M20F?  The parts catalog only lists the -1 hybrid weight not the -7. So the question is which one was tested with the smooth elevators?   

Pandora’s box is now open 

[Igor_U]

12 minutes ago, Gary0747 said:

I measured my elevator when it came off and the weight was 1.60 pounds to 1.62 pounds. So now I am being told these numbers are not correct even though they are correct according to my service manual that applied to the first 540 M20F?  The parts catalog only lists the -1 hybrid weight not the -7. So the question is which one was tested with the smooth elevators?   

No they are correct for the Hybrid, -1 weight which you had. Now, -7 requires 1.09-1.3 lb. as per 68 SM and SB.

Question really is how would solid -7 weight end up on 1967 F? Frank was suggesting that was replaced during the life of the airplane(s). some people on MS are saying factory would just grab and install a whatever they had (-7 would go on C, D and E) but I find that hard to believe. Also, what would they balance the -7 weight on 67 F? That's not a way to build a plane, IMO.

But what would I know....

[Kelpro999]

1 hour ago, Igor_U said:

No they are correct for the Hybrid, -1 weight which you had. Now, -7 requires 1.09-1.3 lb. as per 68 SM and SB.

Now I’m really confused how simply changing AD part due to corrosion issues with an update part that grossly changes static/ aerodynamic state is only being addressed as corrosion mitigation. From reading above the difference between -1 and-7 is approximately 1lb. 
 That’s a significant difference. 

[Gary0747]

1 hour ago, Igor_U said:

Question really is how would solid -7 weight end up on 1967 F? Frank was suggesting that was replaced during the life of the airplane(s).

There must have been a lot of -7 non hybrid weights used since there were only 130 sets of -1 hybrid weights.  The remaining 410 M20Fs in the pre 1968 time period appeared to  have the same balance criteria as the hybrid weights since no distinction is noted in the service manual.     I wonder if the solid -7 elevators were actually balanced to the spec in the service manual?    I see no way to get there with the current -7 weight a full pound heavier than the hybrid weight.

 

[Gary0747]

The other thing that may cause the 540 M20Fs made prior to 1968 to require different balance setting is the bunges are different as well as the elevators.  So if changing elevators pre 68 to post 68 is ever needed the bunges will likely need changing also.