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SB-00036 posted: Inspect outboard elev hinge bracket area of most RV models

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Ok, got my -6 equipped with the -8 tail inspected today.
Enlarged the tooling hole with a long 8mm drill bit... using full up deflection barely cleared the elevator counterweight.

Used the newly acquired borescope from our association, a Teslong Td500 which worked perfectly. The hammered rivet heads are logically on the hinge brackets and no cracks on this 1'500h, with some mild aeros, year 2000 kit machine :)
 

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Finished my inspection today. Finally got to use the bore scope I purchased a while back. No cracks were found.
 
No Cracks

I did the inspection today with a $18 Takmly scope I ordered last week, only had to
open the tooling hole to .250 with a long step reamer.
 

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sheeple maybe? I guess I follow the "best practice":eek: but then i dont know anything. Just seems better to form the shop head on the thicker stuff. Now i see there is an RV8 with a manufactured head on the inside like mine with a crack its not insignificant...might be more....may lead to a different conclusion then....my fav reason still is misalignment of hinges...plus i was a bit surprised those bits were not made with a doubler...

I’m surprised to see just in this brief sampling how many folks did the shop head on the hinge. Wouldn’t argue it’s more logical. If it ends up a hinge alignment issue, it will be interesting to see what models are most affected. With the match drill kits, alignment should be automatic? at least for the hinges, perhaps not for the rod end adjustment. The early kits, 3/4/6, required aligning the hinge holes before drilling. This was done most commonly with a string and visually checking to see if it was centered. One would think that would be less reliable, but we also jigged the assemble. It had not chance of moving around like unjigged match drilled kits might.
 
I’m surprised to see just in this brief sampling how many folks did the shop head on the hinge. Wouldn’t argue it’s more logical. If it ends up a hinge alignment issue, it will be interesting to see what models are most affected. With the match drill kits, alignment should be automatic? at least for the hinges, perhaps not for the rod end adjustment. The early kits, 3/4/6, required aligning the hinge holes before drilling. This was done most commonly with a string and visually checking to see if it was centered. One would think that would be less reliable, but we also jigged the assemble. It had not chance of moving around like unjigged match drilled kits might.

me too..its good to see there are others that have done what I have done...nice to see one has 1500 hours and no cracks with the manufactured heads on the spar. maybe its more hinge alignment issues....perhaps poor de-burring?
 
On the 14 it specifically calls for the shop heads to be on the spar.

Step 9: Rivet the HS-912 Hinge Brackets to the spar using the rivets shown in Figure 1. Place the domed, manufactured head of the
rivets on the bracket.


I believe this is for better clearance for the elevator rolled leading edge.
 
On the 14 it specifically calls for the shop heads to be on the spar.

Step 9: Rivet the HS-912 Hinge Brackets to the spar using the rivets shown in Figure 1. Place the domed, manufactured head of the
rivets on the bracket.


I believe this is for better clearance for the elevator rolled leading edge.

Interesting.
It is kind of a universal practice since the beginning of metal airplane fabrication to put the manufactured head on the outside of the airplane, regardless of thickness. Yes, it’s preferred to have it on the thicker part as it makes it easier to buck and keep the two pieces from spreading as the rivet is driven. I believe it is good practice to have the shop head on the thicker material, when able, but it wasn’t done that way on hinge brackets for most early RV’s, and I’ve seen a lot of them.
Most RV’s have a lot of rivets with shop heads on the thinner material. The .032 to .025 wing skin joint is an example, granted they are flush rivets….
 
It was mentioned that the 9/10/14 models had a different design, and to date, it doesn't appear that anyone has found cracking in any of those models.

Greg, is there a possibility of rescinding the SB in the future for models which show no service history of failures after X years? If so, is it prudent to make doubler kits for these models when no issues have been found? Are we fixing a problem that may not even exist, and in doing so, obscuring future inspections by adding a doubler?
 
"Design Differences?"

It was mentioned that the 9/10/14 models had a different design.

Different design == Thickness of the aft h-stab material; .063" (9/10/14) vs .032" (3/4/6/7/8).

In the case of cracking being found, in other aircraft or in the prior exemplars, I would love to see a really close up view (10X - 20X) of the bracket attach holes, fore and aft side of the spar, as un-molested as possible.

I have a suspicion that builder technique also plays a part in this...
 
Fortunately, if you didn’t go “off plans” in a 14 and close the ends of the horizontal stab., it is easy to see the forward side of the hinge attachment. Just need a flashlight. :D
 
Crack!

2004 rv8 with 950 hrs and very little aerobatics. O360 with no inverted stuff. Only crack of the 16 rivets. At least don’t have to replace spar. Right side of right side bracket. Not builder. I can’t really say builder error, because there have not been any cracks in the other SB’s
 

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Not an engineer...

Anyone smarter than me care to share what types of forces those outer hinge brackets are exposed to?

Thinking about the design, when you push the stick forward, you are commanding those levered lead weights to move upwards which (just guessing) puts a fair amount of downward pressure on the end hinge brackets? Essentially trying to pull the top hinge rivets out of the spar?
 
RV-4 No Cracks
650 hours TT
good amount of gentleman's aerobatics pulling 3.5G max, nothing fancy
Shop heads on the forward side
5th rivet in the center

Thumbs up to the Teslong TE0418 borescope, fit through the tooling hole without modification. Great picture too, nice unit for the money.
 
I did the inspection on an rv4 today. The aft tooling hole was unreachable with the elevator installed. I drilled a hole aft of the fwd elevator spar to insert the borescope. Most of the airplanes around here are filled and fiberglassed. I have little faith that the tooling hole could be located accurately under foam and glass. This particular airplane has doubler plates installed. Somebody was thinking ahead and i doubt it would ever crack. I have 5 more to do this week. I am also drilling and inspecting my harmon rocket.

Titan: When you drill the hole for the boroscope through "foam & glass", will you just leave the open hole, or use some type of cap/fitting to cover it? Or maybe cover hole with tape?
 
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27 year old RV6, > 1000 TT, no aerobatics, no cracks. Another positive vote for the Teslong TE0418.
 
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