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Trim Tab Rigging and SB Write-Up Posted

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Tim Olson

Joined: 25 Jan 2007
Posts: 2875

Posted: Sat Jun 28, 2008 11:04 am Post subject: Trim Tab Rigging and SB Write-Up Posted

I finally am on the road and had my wife drive so I could finish a write

up I've had planned to show the issues with Trim Tab rigging and then a

brief summary about the Service Bulletin.  I may revise it later a bit,

but here is what I have.  Also, none of the other many links that I

updated are ready yet, so the only way to this page right now is by

this link:

http://www.myrv10.com/N104CD/maintenance/20080622/



Feel free to discuss.  I'd like to thank Bill DeRouchey for his input in

the "twisted tail" arena.  I don't know that it will be a major issue

for most people, but it definitely is worth reading the link and

checking it on your own plane.  If you haven't yet done the SB, just

wait until it's all assembled.



Enjoy!



-- 

Tim Olson - RV-10 N104CD - Flying

johngoodman

Joined: 18 Sep 2006
Posts: 530
Location: GA

Posted: Sat Jun 28, 2008 1:28 pm Post subject: Re: Trim Tab Rigging and SB Write-Up Posted

Tim,

That was an excellent article. You answered a lot of questions but, as always, it brings up more questions. My first one is easy. The doubler looks like it interferes with the longeron, but obviously it doesn't. Is it touching the longeron?

My next question is about the operation of the two trim tabs. You explanation was excellent, but it begs the question - why two trim tabs in the first place? I am NOT an aeronautical engineer, so I'm allowed to ask stupid questions (g). Could we not operate with just one tab? If it is too small, could it have been made bigger? If two tabs were necessary, why not sync them together and limit the nose down travel (tab up) to something less?

Probably dumb questions, but it sure has been crossing my mind lately.



John

_________________
#40572 Phase One complete in 2011

Deems Davis

Joined: 09 Jan 2006
Posts: 925

Posted: Sun Jun 29, 2008 5:11 am Post subject: Trim Tab Rigging and SB Write-Up Posted

Tim, EXCELLENT write-up  & synopsis. THANKS !  I also believe that Bill 

DeRouchey deserves a lot of credit for identifying the 'potential' for 

problems down the road and the likely (IMO) link between trim tab 

rigging and the SB. Your write up does a very good job of tying all of 

this information together. To the best of my knowledge, no one that is 

flying has reported any cracks, But the pictures of the 'working rivets' 

in your plane further reinforce the evidence of a twisting force in the 

tail. IMO compliance with the Service Bulletin should be tied to an 

examination and potential re rigging of the trim tabs.



THANKS for the service you provide this community.



Deems Davis # 406

'Its all done....Its just not put together'

http://deemsrv10.com/



 	  Quote:

speckter(at)comcast.net
Guest

Posted: Sun Jun 29, 2008 10:16 am Post subject: Trim Tab Rigging and SB Write-Up Posted

I know that I will get some flames on this, but I am not convinced that the

twisting caused by trim tab rigging is the issue.  All of the other RV

series have a single trim tab on one elevator only as do many other general

aviation aircraft.  Yes this does cause twisting, but not to the extent that

it should be worrisome.  I suspect that there are other design issues going

on in the 10 tail and that the trim tab torque only made it show up as a

fatigue crack earlier than it normally would have if both tabs moved in

parallel.



Steady even torque is not as rough on structures as is osculating torque

such as comes from turbulence.  Even the lowly beer can takes a lot of

torque but not so much bending back and forth.  Additionally the bulkhead in

Van's pix looked bent to me like it was over stressed.



All I am saying is that we don't have enough info or engineering data to

make a definitive diagnosis.  Many possible theories but no proof.



Gary

40274 Flying    



--

AV8ORJWC

Joined: 13 Jul 2006
Posts: 1149
Location: Aurora, Oregon "Home of VANS"

Posted: Sun Jun 29, 2008 12:24 pm Post subject: Trim Tab Rigging and SB Write-Up Posted

As Tim knows, I have discussed in detail with the former manager of the

VANS Proto-type shop the history of the build of N220RV.  He was not

receptive to the possibility of workmanship as the cause.  Seems N220RV

had quite a history on the removal and experimental research of multiple

tail designs directed by management. (Not unlike six attempts to get a

wing that worked on the RV-12). The histrionics of single tab and dual

tab were discussed in detail.  Using the airframe for demos and the

repeated demonstration of stalls to John Q. Public had something to do

with it.  The horizontal tips deflect 3" positive and negative with a

noticeable buffet.



Alex D has not had a problem, Mike Seager did not have a problem, so I

have concluded it is unique to N220RV.  No one is mentioning the other

issue of the J stringers in contact with the frames and bulkheads.



I am following the respected advise I received and using a modified and

doubled two F-1010s back to back construction technique.  Others should

be fine installing the SB patch and sleeping at night.  Been to the

mountain, read the tablet, listened to Moses and returning to prayer.

There is history, engineering  and information on this issue.  It is not

available for public consumption.  That is proof enough for me.



John Cox

40600 KUAO



--

rene(at)felker.com
Guest

Posted: Sun Jun 29, 2008 12:38 pm Post subject: Trim Tab Rigging and SB Write-Up Posted

One note.....Mike Seager normally trains in N220RV, so technically he did

have a problem. When I went up for my transition training, I did it in

410RV, but Mike told me that he normally does it in N220RV but could not

because it was in the shop.......that was the end of Feb this year. 



Rene' Felker

RV-10 N423CF Flying

801-721-6080

--

AV8ORJWC

Joined: 13 Jul 2006
Posts: 1149
Location: Aurora, Oregon "Home of VANS"

Posted: Sun Jun 29, 2008 2:51 pm Post subject: Trim Tab Rigging and SB Write-Up Posted

Flying the aircraft and having a problem are two entirely different

events.  I was not aware that Mike had any problem other than the lack

of availability.  He has been great to point out the horizontal

performance and airmanship issues which can improve safe flight.



I would love to hear more about his having a problem and think many

builders would like to know more about cause and effects on N220RV.



So far, I have not heard of any aircraft other than N220RV which an

inspection finding.  It was valuable learning of the development

history.



John

do not archive



--

Tim Olson

Joined: 25 Jan 2007
Posts: 2875

Posted: Sun Jun 29, 2008 3:15 pm Post subject: Trim Tab Rigging and SB Write-Up Posted

Oh I totally agree that it isn't likely to be a cause.

And I agree fully regarding the fact that other planes have

a single tab too, which is why I mentioned it.  I don't

think it's likely to cause many builders a problem.  The thing

is though, having one tab going one way and the other going

opposite isn't at all what a person would want, so I wanted

to point out how just doing things "normally" may result in

a slight amount of this situation.  I know I had it, and

I didn't see the twisting and the asymmetry.  I can only

think though that the further one's tabs are off, very

quickly the forces could get higher and higher.  So, it's

just plain good sense to make sure everything is rigged right.



I'm not sure what caused the cracks on that plane, but I can

easily see it being a combination of:  Some big turbulence

hits, lots and lots of tail shuddering stalls, and potentially

maybe not deburring well around that notch.  Hard to blame

the deburring much though, because there is definite deformation

of that bulkhead.  Oh well, it happened....I'm just glad

it's stronger now.



Tim Olson - RV-10 N104CD - Flying

do not archive

gary wrote:

[quote] 

 

 I know that I will get some flames on this, but I am not convinced that the

 twisting caused by trim tab rigging is the issue.  All of the other RV

 series have a single trim tab on one elevator only as do many other general

 aviation aircraft.  Yes this does cause twisting, but not to the extent that

 it should be worrisome.  I suspect that there are other design issues going

 on in the 10 tail and that the trim tab torque only made it show up as a

 fatigue crack earlier than it normally would have if both tabs moved in

 parallel.

 

 Steady even torque is not as rough on structures as is osculating torque

 such as comes from turbulence.  Even the lowly beer can takes a lot of

 torque but not so much bending back and forth.  Additionally the bulkhead in

 Van's pix looked bent to me like it was over stressed.

 

 All I am saying is that we don't have enough info or engineering data to

 make a definitive diagnosis.  Many possible theories but no proof.

 

 Gary

 40274 Flying    

 

 --

rene(at)felker.com
Guest

Posted: Sun Jun 29, 2008 5:38 pm Post subject: Trim Tab Rigging and SB Write-Up Posted

Now that I am not at work and have a couple of minutes......before the kids

come and attack me....



As I reported here, I had a heavy left wing during my initial flight

testing, and in the end I attributed it to three things.



1.  Me being to fat and not giving enough credit to that fact.  I have since

always burned the left tank down when I am the sole occupant.  That was the

easy one.

2.  Flap rigging, my right flap was 1 degree lower than the left flap.  It

was do to a little interference between the inside edge of the flap and the

fuselage.  I was able to file down the flap a little, getting a better fit

and got the rigging right.  I also re-rigged the ailerons, but it was very

minor.  After that I felt I still had a heavy left wing.  Trim handled it,

but I felt I was using to much trim and I could see the ailerons were not in

trail in level flight.

3.  The last thing I did was re-rigged the elevator trim.  When I first

flew, I felt I was using way to much nose down trim after takeoff and in

cruise flight.  After to talking to some other flyers, I felt that may be

more normal.  I walked through the rigging procedure several times and was

not happy with the way the left trim moved......so I tried to fix that.  At

about a degree at a time I changed the starting position from 35 down to 34

down and so on.  Did a test flight each time, trying to determine if I was

changing anything.  Handling stayed the same.  In the end, if I remember

correctly, I ended up a little under 33 degrees.  With that, the left comes

up and then goes back in trail as I go to full nose down.



Now after doing all that, I do not notice the heavy left wing.....and I am

still fat, so at least I kept one variable constant.



Tomorrow is my first real cross country, me and my wife are headed to Vegas

for a couple of days to met up with my Brother and friends.  It will be the

first test where I have not had something else to do except pay attention to

the plane.

Rene'

801-721-6080

--

speckter(at)comcast.net
Guest

Posted: Mon Jun 30, 2008 6:07 am Post subject: Trim Tab Rigging and SB Write-Up Posted

This is in the department of SWAG.  It looks to me like someone pushed down

on the horizontal stab and bent things doing so and it was flown like that

for a while.  But as I pointed out in my comments this is all conjecture.



Gary

40274 Flying



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