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RV horizontal stab crack reporting thread

RV4 S/N 63
~1675 hrs
o320 wood prop
repaired by builder in '01 after off-airport landing incident
minimum acro (occasional 1g roll)
Two small cracks <0.25" radiating vertically from a single rivet left side outbd hinge bracket
 
No Cracks!

Borescoped the rear stab spar of RV-7 C-GCPD this morning, as per Van's SB 00036. No cracks found.
 
elevator removal

Any hints on removing the RV6 elevator from the stabilizer? Like how to get to the nut and bolt through the tiny inspection hole?
 
A little data analysis

CF86301, I hope I'm not stepping on your toes here by reporting a little analysis of the data in your Google spreadsheet.
Total responses posted: 255 -- Taildraggers 156, Nosedraggers 99
Total with cracks 38, without cracks 217

Of the 38 with cracks: 33 taildraggers, 5 nosedraggers
RV-3: 2, RV-3B 1, RV-4: 3, RV-6: 4, RV-6A: 1, RV-7: 7, RV-7A: 2, RV-8: 16, RV-8A: 2
Total time reported: minimum 270, max. 3382, avg 1257, median 1000
Factory rivet heads: FWD 2, AFT 23, not reported 13

Tailwheel without cracks: 123. Factory heads FWD 30, AFT 50 (remainder not reported)
Nosewheel without cracks: 94. Factory heads FWD 17, AFT 41 (remainder not reported)
 
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Worked great

I recently completed the repair for a crack in the left horizontal stabilizer rear spar on mt RV-8 as detailed in SB-00036 Rev3. I devised a tool for holding the repair doubler on the front side of the spar while all pieces were Clecoed in place.
This was the easiest part of the whole repair. Removing three rivets from the outer rib, and seven rivets from the rear spar will permit installation of the repair doubler. After removing the 10 rivets from the top skin and the rivets from the hinge brackets, and stop drilling the cracks, the nested spar doubler and hinge brackets were positioned.
A single Cleco was placed through each bracket, nested spar doubler, and spar. The skin was then flexed up and the repair doubler (attached to the doubler positioning tool) was slid over the top of the spar and rotated down into position. It is important that the wire holder clearance between the top of the repair doubler and the handle portion of the tool permits vertical alignment of the rivet holes in the doubler with the Clecos. This can easily be adjusted to get the right clearance.
Once the doubler rivet holes are aligned with the Clecos the tool handle can be pulled aft to hold the doubler in place while the Clecos are squeezed to permit them to engage the doubler. It should be possible to verify that the Clecos have engaged the doubler by viewing the repair doubler from the space between the flexed skin and the end rib. Once the Clecos have engaged the doubler you can contine Clecoing the rest of the rivet holes and proceed with riveting.
The 10 rivets can be removed from either the top or the bottom of the horizontal stabilizer. I believe from the top is easier, the positioning tool can be reversed to work from the underside. The only difference is the side which is opened up and flexed will have four addional rivets removed.

Was able to use your idea to install the repair doubler with only 10 rivets removed from the rear spar, since I had just closed in the end of the end rib with foam and epoxy.
 

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RV7 1365.9 TT
Cracked
Light acro & rough fields

Four on each side emanating from corners. One is on middle rivet about 5/16 long.
 
CF86301, I hope I'm not stepping on your toes here by reporting a little analysis of the data in your Google spreadsheet.
Total responses posted: 255 -- Taildraggers 156, Nosedraggers 99
Total with cracks 38, without cracks 217

Of the 38 with cracks: 33 taildraggers, 5 nosedraggers
RV-3: 2, RV-3B 1, RV-4: 3, RV-6: 4, RV-6A: 1, RV-7: 7, RV-7A: 2, RV-8: 16, RV-8A: 2
Total time reported: minimum 270, max. 3382, avg 1257, median 1000
Factory rivet heads: FWD 2, AFT 23, not reported 13

Tailwheel without cracks: 123. Factory heads FWD 30, AFT 50 (remainder not reported)
Nosewheel without cracks: 94. Factory heads FWD 17, AFT 41 (remainder not reported)

Nice work Doug.
I think propeller balancing is a factor to be considered in your analysis.
 
RV8 1485 hrs stab cracks. Spar replacement needed

1485 hrs RV8. Found a couple of cracks on the right stabilizer rear spar. Unfortunately the cracks are in such close proximity to the bend radius of the spar that the factory recommends spar replacement. Yuck.
 
80027

2004 RV-8 TD
1000 hours
Counterbalanced IO360
Balanced Whirlwind prop
Minimal aerobatics and rough field opns
No cracks
 
Familiar airplane......

2004 RV-8 TD
1000 hours
Counterbalanced IO360
Balanced Whirlwind prop
Minimal aerobatics and rough field opns
No cracks

Hey......I think I have seen that airplane before!!!! Beautiful RV-8!

First flight not yet done on my build....ordered kit and was installed anyway....better safe than sorry! A great fellow airport buddy Rob Brooks did the SB while I was gallivanting in Anchorage for 18 days for work!!! What a great community these RV folks are!!!
 
No Cracks

No Cracks
RV-8 #80668
650 hours TT
Very light aerobatics
Angle valve IO-360
Old fashioned Hartzel prop, not balanced
 
1997 RV-6
692 hrs total time
high compression IO-360 (195 hp)
composite Sensenich prop, not balanced
no acro or grass fields

No cracks.
 
No Cracks!

2000 RV6A
860 Hrs. Tach Time
Light Aero
Factory Heads Forward, shop heads aft
5 Rivets on inboard brackets
4 Rivets on outboard brackets
Oversized tooling hole to 3/8" to Borescope
Sensenich Fixed Pitched Aluminum, Dynamically Balanced to 0.002 IPS
Almost exclusively on asphalt, some good grass
NO CRACKS
:D
 
Shop head location and crack relationship.

I would suggest that a pie chart or graph would be nice to see if there is a correlation between the factory head and the shop head location and cracks.

Once the rivet swells and the shop head begins to form there are additional compressive loads under the shop head on the spar. If the shop head is on the aft side (forming on the steel bracket) the steel bracket can handle much higher stresses than the aluminum spar.

Good rule to follow-

If you have the option, shop heads on the thicker or stronger material, factory heads on the thinner and weaker material.
 
Passed Inspection

2001 RV8
1250 Hobbs Hours
Spent 3 years on fairly smooth grass strip, otherwise on pavement.
Max 4G aerobatics.
No cracks observed.
 
Data also submitted on the online survey link.

2000 RV-6A
772 hrs
IO-360, Catto Composite 3 lade prop
Shop heads aft
no acro, asphalt only in my hands, but have log entries of the builder landing on grass strips many many years ago.
No cracks found
 
...

If you have the option, shop heads on the thicker or stronger material, factory heads on the thinner and weaker material.

Sounds reasonable. I built my tail kit at a build center in Griffin, GA, with a very talented young man guiding me - and a few other guys on the forum - and I recall him giving advice on this exact thing, but honestly can't recall the details. In the end my shop head is towards the rear, which is where the steel bracket is.
 
Me too

Sounds reasonable. I built my tail kit at a build center in Griffin, GA, with a very talented young man guiding me - and a few other guys on the forum - and I recall him giving advice on this exact thing, but honestly can't recall the details. In the end my shop head is towards the rear, which is where the steel bracket is.


My RV7A Empennage was built with the help of the Tech at Griffin GA. I was told that the upset head should be on the thickest or harder material.. not sure if that is from AC 43 .. but we did our that way too.. No Cracks
 
Hello all,

RV7 180hp/GA200L, first flight 05/2017
750hrs with many acros!!!
Shop heads aft
No cracks.

Regards, Xavier (France)
 
C-GCPD Horizontail tail

Checked Horizontal tail with borescope as per the SB. No Cracks ! 730 hours TT.

Cheers
Dave
 
SB-00036- small diameter borescope (no need to enlarge tooling hole)

Not sure if this was discussed and I may have missed it, but I found a borescope with a head diameter small enough to insert through the tooling hole in the outboard rib without enlarging it.

I know enlarging the hole isn't a big deal, but if this helps anyone I thought I'd pass it along.. 3.9mm head easily passed through on my H-Stab. Found on that big behemoth online retailer

Best part- No cracks!
 
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No cracks but it looked like there might have been

2,700 hours, all kinds of aerobatics... no cracks.

Visual inspection with a wee bitty camera showed several small black lines that could possibly be cracks but my suspicion was that they were formed from lubricant penetration and air pressure.

Removed the brackets and performed a dye penetration test finding no cracks.
Oh well, lots of effort to litter the inside structure with drilled out rivet debris, might as well install the new reinforcement parts. The new stiffener ties the bracket loads across the spar flanges into the skins and is significantly stronger. I also added the interior doubler.

Peel back the bottom skin to clean up and reach in to drive solid rivets, put it all back together, go pull 5 gees. Works the same as before 😉

A full 8 hours of work… it’s still quite a bit of fun doing maintenance even though this does not appear to have been needed.
 
Condition inspection just completed

RV-10, 100 hours TT, based at grass strip, prop not dynamically balanced, shop heads forward, no cracks.
 
No cracks

RV7 - inspected from the long side, no cracks on either side. 260hrs. IO360M1B
 
What borescope?

Not sure if this was discussed and I may have missed it, but I found a borescope with a head diameter small enough to insert through the tooling hole in the outboard rib without enlarging it.

I know enlarging the hole isn't a big deal, but if this helps anyone I thought I'd pass it along.. 3.9mm head easily passed through on my H-Stab. Found on that big behemoth online retailer

Best part- No cracks!

Can you share what borescope you used?
 
RV10 horizontal Srab rear spar

400 hours and no cracks. I always install my gust lock when parked outside, even for lunch. This is very important for the rudder bottom mounts, but I am uncertain how much difference it makes for the horizontal stab rear spar.
 
RV-8 built 2002, 700 hours, formation aerobatics (prior owner), some grass landings. Shop heads aft side of spar. No cracks.
 
Why are we listed on this SB?

Just like every other RV-9, -10, and -14 ever made….no cracks.

Why list a plane with no known issues on a SB ? Caution is appreciated but zero dot zero is not caution, it’s paranoia.
 
Before someone discovered it, the problem was unknown on any model RV. C'mon, peeking through a lightening hole with a good light can't be that hard...
 
SB00036

RV-6
2010 hrs
mfg head fwd
light acro (no snaps)
landings on grass and dirt

no cracks

Laird
 
RV-4 No cracks

1995
RV-4
980 hours
Lycoming O-360-A1A
Hartzell c/s
No dynamic balancing
Over 200 aerobatic flights
No cracks
 
Just like every other RV-9, -10, and -14 ever made….no cracks.

Why list a plane with no known issues on a SB ? Caution is appreciated but zero dot zero is not caution, it’s paranoia.
I don't know but would guess that the HS designs are similar enough between the older and newer models that Vans has reason to believe it could occur in the newer model fleet as it ages.
 
I don't know but would guess that the HS designs are similar enough between the older and newer models that Vans has reason to believe it could occur in the newer model fleet as it ages.

It is a different tail altogether, not a matter of older vs newer. The mothership says “an over abundance of caution”.
 
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