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Elevator and Stab rigging S/N Specific?


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Had the question pop up as to "why" the elevator rigging changes between different S/Ns of vintage Mooneys according to the TCDS sheets. I heard it mentioned once a long time ago but can't seem to drag it from the memory bank right now. A search of records here hasn't shed any light either. Anyone remember or know why Mooney changed the rigging? 

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rob47v Don't quite know what you are saying but I've included a clip from the TCDS sheet on C models (Ds Fs are the same) but this shows how the throws change at certain S/Ns and they also changed the bungee number. This is why changing elevators from one airplane to another (even of the same model) can become an issue if this is not known. I knew at one time why they did this I just can't remember now after 40 years. I do know that 2 Mooneys went off the end of Stockton Airport, CA only because they had the elevator trim set at full up on T/O and they couldn't rotate. 
 
 
Control Surface Movements (Aircraft with serial numbers up to 690001) 
 Wing Flaps .................................... T.O. Position .... Down ........ 15° ± 1° 
 ....................................................... Landing ............ Down ........ 33° + 0°, -2° 
 Aileron .............................. Up ....... 12½° to 17° ...... Down ........ 8° ± 1° 
 Aileron static position ............................................... Down ........ 0° to 2° 
 Elevator ........................... Up ....... 24° ± 1° ............ Down ....... 10½° ± 1° 
 Rudder ............................ Left ....... 23° to 24° ......... Right ........ 23° to 24° 
 Stabilizer (L.E.) ................ Up ....... 1 to 2½° ............ Down ....... 4½° + 5° 
 
 Elevator Trim Assist Unit With stabilizer set at 3½° negative setting to the thrust line, adjust trim assist unit 
(740044) for elevator up angle of 19° ± ½° at the zero spring travel position. 
 
 (Aircraft with serial numbers 690001-700091, 20-0001 and up) 
 Wing Flaps .................................... T.O. Position .... Down ........ 15° ± 1° 
 ....................................................... Landing ............ Down ........ 33° + 0°, -2° 
 Aileron .............................. Up ....... 12½° to 17° ...... Down ........ 8° ± 1° 
 Aileron static position ............................................... Down ........ 0° to 2° 
 Elevator ........................... Up ....... 22° ± 2° ............ Down ....... 22° ± 2° 
 Stabilizer (L.E.) ................ Up ....... ½° to 1° ............ Down ....... 5¼° to 5¾°
 Rudder ............................ Left ....... 23° to 24° ......... Right ........ 23° to 24° 
 
 Elevator Trim Assist Unit With stabilizer set at 3½° negative setting to the thrust line, 
 adjust trim assist bungees (740188) for elevator position of 10° ± 1° at the zero spring 
 travel position of the bungees. 
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Sorry for the confusion. As I stated or tried at lest usually S/N don't have specific rig differences unless changes where made during production which makes it a effectivity difference usually is done when a newer model which may be different in design attachment or parts which might include vendors. If brackets change bungees, or actuators then at that point the listed model will have a difference in the rig  maint procedure do to the difference in parts, or as stated difference in attachment points. Heck using of different hard ware at time will call out changes in effectivity.  

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My M20B model has a rudder that has about 11 degrees less throw than the subsequent C models and above.

 

Phil

Phil . you can replace the last bellcrank in the rudder rod "train" to get the extra throw on the rudder for the B , easy retrofit..... 

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Just asking the question and not criticizing but:

On a Model B the listed rudder throw is 18 degrees L and R

On a C, D, E, F, it is 23-24 degrees, max of 6 degrees more, not 11 more, according to the TCDS.

Phil, does your throw match what is called for on the TCDS? 18 degrees? If it does, it is at the max legal throw even though the Cs have a different part and go further. Here is a link to the FAAs website to check your allowable rudder throw on the TCDS.

 

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/e74974516b2c5ee886257c3500689e02/$FILE/2A3_Rev_53.pdf

 

I'm not saying that there is no approval to use some other part to increase throw but it would have to go through a full flight test regime to get such an approval as it affects the basic flying qualities of the airplane. If there is such an approval I would like to know about it so I can advise those I come in contact with (yes, really, I'm very interested in having correct information for people, if it's available as a mod, I really do want to know about it) but to legally do such a change requires some kind of written approval traceable back as a modification to the original Type Certificate.

 

Just because a certain part fits doesn't mean it's legal to use it. This can also affect your personal liability and your insurance if you have an accident. If an A&P installs it without knowing of such an approval HE will lose his license  as he is required to ascertain the legality of each part he installs before he installs it and sign off the installation according to some "approved" process. If you install it and it is not logged (you can't sign the log book unless you are an A&P (under most circumstances) and you have an accident, your insurance may not be valid (not maintained according to the regs), you could be violated for performing a/c maintenance without the proper credentials (A&P)  and God forbid anyone is hurt, you could loss everything you have in court.  

 

I guess this is my biggest Achilles heel and it rears its ugly head even here on this forum and I won't apologize for it. In doing a/c maintenance for almost 50 years I have seen things done by owners (even well meaning owners) that is not legal, or, in most cases, not even safe. I know of one Piper Pawnee on a farm that was bought new and has never had an annual or parts bought from an approved source since it left the factory. At least the owner will only kill himself if he goes down. On my own Mooney, when I bought it, it had a battery lead to the starter made from automotive cable and it had been maintained by an A&P even. I could go on and on about what I have found on airplanes (even when the owners thought they were doing right).

 

I have lost many friends in a/c accidents due to ignorance, stupidity or error. This is not your high school Chevy you're working on. You could pull over and park your car, you can't do that in your airplane. I just don't want to see any more friends (and yes, you all are my friends if you fly airplanes) go west in airplanes. I teach flying and a/c maintenance the same way, if it ain't legal, it ain't safe.

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As long as you have an FAA inspector at your local fesdo office that will use practical sense, approvals are a cinch, but keep in mind that that's a rare case. These guys are paperwork bound. Hence if the paperwork is straight the airplane is straight. And well all know that's not the case many times. Or you could be so lucky and have a friend or have a great relationship with a DER. That would open-up all kinds of possibilities.    

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Letter from the factory noted except that it's still not legal to do unless there is a change to the TCDS reflecting the approval for higher throws and p/n change OR and STC accompanies the work OR a DER signs it off OR a FSDO gives a Field Approval or maybe a Service Bulletin. I can't as an A&P do that work on just a letter from the factory. I'm willing to guess there was more to it than just change the part and sign it off. I'd really like to know what approved process LASAR used to install the part and change the throws. 

With the TCDS showing the "conformity" of the aircraft, I can't deviate from that unless I have some other "APPROVED" paper work to go by, nor can any other A&P. Especially with something that affects the basic flying qualities of the airplane.

I won't disparage Bill Wheat's words as he know these planes as well as anyone ever did BUT there has to be more to it than just change the part and increase the throws beyond what the conformity calls for to be legal.  Mr. Wheat can't, on his own volition, change a conformity issue by just a letter. There has to be a legal means to do it,  

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Bill was the DER at Mooney and I believe Lasar has one on staff also. I've saw several things signed off by DER's with the notation "no further engineering work needed" when it was a change that was incorperated into a later version of the airframe.

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There is an out to something like this. At least from I've been told it works I've known of several IA which have done mods in this manner. That is, if there is an aircraft which has been moded, and it has been approved previously with a 337,then that work can be accomplished on another aircraft and be signed off accompanying a copy of the original 337 on which the approval was done. Now the work must be performed as specified on the approved 337, no deviations allowed.        

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rob47v,

Are you saying that if a 337 has been approved for any modification, that as long as you adhere strictly to there procedure, you are automatically entitled to do it. Or is that merely a piece of evidence that means your FSDO is likely to approve yours.

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I'm working with my mechanic (please, no comments about experienced mooney expert) right now to redo the rigging on the elevator and stab on my 1967 M20F. S#670093

Question - how do you determine the neutral position for both, or the neutral trim position?

How do you determine the zero spring travel position?

 

Could anyone provide some how to, 123 steps to the process, if one was starting from the beginning, assuming trim, stab and elevator were all wrong? 

Thanks a bunch!  I know others can benefit from a great answer since I've done a bunch of reading and only get pieces of info here and there!

Barry

 

Control Surface Movements (Aircraft with serial numbers up to 690001) 
 Wing Flaps .................................... T.O. Position .... Down ........ 15° ± 1° 
 ....................................................... Landing ............ Down ........ 33° + 0°, -2° 
 Aileron .............................. Up ....... 12½° to 17° ...... Down ........ 8° ± 1° 
 Aileron static position ............................................... Down ........ 0° to 2° 
 Elevator ........................... Up ....... 24° ± 1° ............ Down ....... 10½° ± 1° 
 Rudder ............................ Left ....... 23° to 24° ......... Right ........ 23° to 24° 
 Stabilizer (L.E.) ................ Up ....... 1 to 2½° ............ Down ....... 4½° + 5° 
 
 Elevator Trim Assist Unit With stabilizer set at 3½° negative setting to the thrust line, adjust trim assist unit 
(740044) for elevator up angle of 19° ± ½° at the zero spring travel position.
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The zero point for the stabilizer/elevator is in relation to the zero point for the thrust line. The skin lap on the aft fuselage side is the zero thrust line. The aircraft is leveled fore and aft by this line. The elevator travel board is put on the elevator and the elevator is trimmed "aircraft nose up" to 3 1/2 degrees. At this point, the elevator will be displaced from a "trail" position in an up elevator position. This is the elevator setting at the bungee zero spring travel setting. It is adjusted by tightening or loosening the nuts on the bungees.

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