What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Listen to the sounds your airplane makes....it may save your butt.

Walt

Well Known Member
While doing a panel upgrade and condition inspection on an RV4, I was hearing a very slight scraping sound when the stick was pushed full forward, obviously one of the elevator torque tubes was hitting something in that position and for a moment, I considered letting it pass, it's was one of those things you say to yourself how often does one really use full down stick so is it really a problem. After locating the area I found it to be under the passenger floor pan which of course is riveted down and the flap mechanism is bolted on top of it, so this was not going to be a 5 minute job. But letting it go kept nagging at me so I decided to just tear into it and find out where the interference was, have a "quick" look at the tube to be sure it wasn't damaged and grind off the offending material.

Well to my surprise (and relief) when I finally got access to have a look I was glad I did, the torque tube had a huge gouge in it that looks to be most of the way through the tube :eek:

So new parts are on order and this is one that I'm really glad I took the time to have a look before it got worse... much worse.

So what to take away from this, don't let anything go that doesn't feel or sound right, find out what it is and correct it.
This is absolutely mandatory for flight controls no matter how "minor" it seems!

Controls should move from stop-stop (this means HIT the stops) with absolutely no binding or funny scraping noises!

BTW, this isn't the first time I've had to replace torque tubes due to damage from chafing on structure but this one was probably the worst/scariest (you may survive a broken aileron tube but the outcome of a disconnected elevator is probably going to make for a really bad day).

IMG_5617.JPG
 
Last edited:
For all the times you dug into something and went "huh, nothin". Then you get the payoff with one like this.
 
My old friend, Tony Bingelis said it this way "machines are always talking to you, you have to learn to listen".
 
Similar

I had a similar issue this past week. I noticed one day that my elevator was sticking ever so slightly in the full up position. Not too much, but just not quite right. Hmmmmm....
I tore into it starting at the elevator bearings working forward to the rod end-elevator connection. no problem there. The pitch servo connection and rear bullhead interconnect looked okay.
I found it at the rear stick. The forward pitch tube rod end bearing AN3 bolt protruded a little to far. When the stick was back (elevator up) the bolt threaded tip was touching the interior of the weldment and sticking ever so slightly.
One washer under the bolt head fixed that.
It must have been that way for 130 hours and I never noticed before. Colder weather???
Anyway, she squawked - I listened.
Don
 
My old friend, Tony Bingelis said it this way "machines are always talking to you, you have to learn to listen".

My wife always laughs at me when I say machines have souls and we need listen to them when they talk ;)

I had a similar issue this past week. I noticed one day that my elevator was sticking ever so slightly in the full up position. Not too much, but just not quite right. Hmmmmm....
I tore into it starting at the elevator bearings working forward to the rod end-elevator connection. no problem there. The pitch servo connection and rear bullhead interconnect looked okay.
I found it at the rear stick. The forward pitch tube rod end bearing AN3 bolt protruded a little to far. When the stick was back (elevator up) the bolt threaded tip was touching the interior of the weldment and sticking ever so slightly.
One washer under the bolt head fixed that.
It must have been that way for 130 hours and I never noticed before. Colder weather???
Anyway, she squawked - I listened.
Don

Although I appreciate the Kudos I really didn't make this post because I need another pat on the back or "great job walt".

If I can inspire just one post like Don's above that is my intent.

The fact is some folks build spectacular airplanes while others probably should have found a different hobby. I only get a chance to look at small number of RV during the year and I find what I consider serious problems on probably half of them. So I'd like to see folks take their maintenance more seriously.

As that old saying goes:

aviation.jpg


Happy Holidays!
 
Last edited:
Wow

Thanks for the post to give us all another slap in the face to wake up
and get a reality check!! Great Christmas present that will help make
for a better New Year!

Merry Christmas Walt!!!
 
So out of morbid curiosity...

...specifically what was the "something" that the torque tube was binding against? (A pic would be cool!) And on another level: Why was it binding on THIS particular RV-4 and not on any of the others? How are you going to prevent the NEW torque tube from binding on the same thing? --Mike
 
...specifically what was the "something" that the torque tube was binding against? (A pic would be cool!) And on another level: Why was it binding on THIS particular RV-4 and not on any of the others? How are you going to prevent the NEW torque tube from binding on the same thing? --Mike

It was one of the thin (.020) horizontal floor stiffeners, a small relief contour ground out of the stiffener cured the interference. I've had to do this before on both elevator and ailerons when the torque tubes chafe structure, but this particular one even surprised me on how deep it had gone from what seemed like a "minor" scraping sound. The situation was likely worse when someone was sitting in the back seat due to downward deflection of the floor.
 
Flight Controls

When I was a student pilot flying a C-150 at the time, I was performing final control check before entering the runway and elected to return to the ramp. I felt a slight resistive force when turning the yoke full right. It felt like a slight detent kind of action if you can imagine. I returned the keys to the keybox and put a "Grounded" tag on the same key. I called the maintenance head and told him I had grounded the airplane and for what cause. He wasn't too please with me because the weekend was coming up and weather was perfect for flying - read the airplane was fully booked. Well, I spoiled plans for a bunch of students.

Jump to the conclusion...The aileron piano hinge wire had somehow failed - I never saw it and don't know the details. Maintenance man called me back later in the day and said that I had made the right decision. He was very concerned that had flight(s) continued, an aileron jam near a full throw position could have occurred. You don't survive those unless all of the ration of altitude for the day is above you while you are still safely on the ground.

Be sensitive to something unusual in the flight controls.
 
Funny Sounds

Thanks Walt for posting this.

I'll definitely keep this one in mind if I hear sounds that I'm not sure of.

This is what I love about VansAirforce.net

Thanks Doug.
 
Not just RV4

It was one of the thin (.020) horizontal floor stiffeners, a small relief contour ground out of the stiffener cured the interference. I've had to do this before on both elevator and ailerons when the torque tubes chafe structure

Not specific to RV4. My 7 had the same problem. Minor scraping noise with elevator movement in one spot was noticed by my designated co-inspector :rolleyes:
during the condition inspection. Nothing needed to be replaced but a relief had to be cut in structure and the tube/struc cleaned up from where it was rubbing.
 
Not specific to RV4. My 7 had the same problem. Minor scraping noise with elevator movement in one spot was noticed by my designated co-inspector :rolleyes:
during the condition inspection. Nothing needed to be replaced but a relief had to be cut in structure and the tube/struc cleaned up from where it was rubbing.

Hmm I wonder how many RV6 have the same pushrod scraping the top of the cut out in F-605 and hitting the underside of the flap cover .....
 
Last edited:
Same here on my -7A...elevator pushrod rubbing on the cutout in the rear baggage bulkhead (whatever part number that is). Found during construction, relieved the hole with sandpaper, cleaned it up, and then even put some UHMW tape on the pushrod in that location just in case it ever rubbed again (under G forces?), checked each annual.

I'd guess a *lot* of planes have a similar issue...hopefully, they're caught during construction or A/W inspection.
 
Prepping right now for my first condition inspection just before Mel shows up for my AI, and yesterday I heard that same type of minor rub coming from my right aileron. Haven't had time to investigate it yet but I'm sure I'll be pulling that apart to get to whatever it is...
 
Scraping sound

I had to remove stiffener material to clear a) aileron servo arm and b) elevator push rod on my RV--8. Easy to do once point of interference identified. As mentioned, load on the floor can increase the need for relief.
 
When I was building the fuselage for my 7A, I had some unexpected rubbing of the elevator pushrod, where it passes through the F-705 bulkhead. It made a whining or groaning noise as I moved the stick forward and back. It took me a while to locate where it was coming from. I put an inspection mirror in the channel under the tube and took this picture. You can see where the rubbing was taking the primer off the tube:

100_7498%20(Small).JPG


The solution, after consulting with Vans and here in these forums, was to carefully file away a bit of material to give proper clearance. Then the obvious smoothing and deburring, to give this result:

100_7504%20(Small).JPG


Here it is after re-priming, using a Q-tip soaked with primer:

100_7505%20(Small).JPG


After putting it all back together, there's no more rubbing, noise, etc. I learned that apparently this is quite common in the RV-7 or 7A. For much more discussion and pictures, you can visit my log page here:

Elevator pushrod Rubbing Problem
 
Today during the annual inspection, my friend (who is an aircraft mechanic) noticed sounds very similar to those described by Walt and listened... aka decided to find the cause.

Guess what - it seems like we have pretty much exactly the same issue:
fz5k4i.jpg

sg1hzs.jpg


Our RV-4 was built in the late 1980s and has around 1400 hours total time. The scraping sounds occur only at near full forward stick and I guess we have just got used to them... fortunately my friend is a pro and took the time to investigate!

I have emailed Van's for recommendations and an order for new part(s) will presumably follow. Meanwhile any suggestions from you guys would be greatly appreciated.

Regards,

Trond M.
 
We listen

Walt,

Some of us really do listen, and often in silence.

In my case, after reading posts here, I go back to something I thought was good, but had an aspect that didn't sit quite right with me. I just didn't have an easy fix when I first encountered it.

Over time, they eat away at me, until I realize I won't take her up for the first time until it has been dealt with.

My biggest two were fuel pumps and ECUs that over time I was sure would vibrate and cause an issue. In both cases, the nag got worse as I worked on other parts of the build. Eventually, I had a solution that not only worked but I also really liked.

It's a mindset that you either have from day one, or you need to build over time.

But for sure, it is posts like this that keep us questioning how we are doing, and could we be doing better. Keep them coming, they are very much appreciated.
 
Back
Top