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  #1  
Old 06-05-2012, 09:35 PM
Rob's RV9A Rob's RV9A is offline
 
Join Date: Dec 2010
Location: WASh, DC
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Default Vertical Stab Attach Plate Crack

This is my first post, and I want to advise what I found removing the panels and fairings for my condition inspection.

While doing the Condition Inspection on my RV9A I found this fault on the vertical stabilator attach plate F-981. For the RV9A this part is visible after removing the vertical stabilizer fairing. It is the top right bolt on F-981. You can see the crack is prevalent on the right side of the bolt and extends left of the bolt about a 1/16. In addition, you can see all four-attachment boltholes are elongated. It is obvious at some point the attachment bolts holes had been re-drilled and to move the vertical stabilator boltholes upwards thus lowering the whole assembly. You can also see the bushing for the manual trim cable is missing. The repair is to remove the whole empennage and carefully drill out the rivets, replace F-981. Both parts $6.83 from Van’s. Hours to repair…….. a few. So while the tail is off I will be looking for other obvious anomalies.

The original builder completed the airplane in 2001; I am the third owner after the builder. Total airframe time is 815 hours. I want others to see taking off that fairing and not just for a quick look deserves the attention to really inspect the attach points.

The pictures are at the following link if I goober the picture post here. http://s1254.photobucket.com/albums/hh616/RV9aer/[/IMG]





Last edited by n5lp : 06-06-2012 at 09:12 AM. Reason: To show pictures
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  #2  
Old 06-05-2012, 11:38 PM
ronoc74 ronoc74 is offline
 
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Default

If I remember rightly, these holes are pre-punched elongated. The problem with this is the sheared edge from the punch, with its fine cracks, won't be tidied up by match drilling with the HS spar. It would need to be done separately. I guess if it's left as a raw edge this is the result.
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  #3  
Old 06-06-2012, 12:30 AM
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Mike S Mike S is offline
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Default Welcome to VAF!!!!

Quote:
Originally Posted by Rob's RV9A View Post
This is my first post,
Rob, welcome aboard the good ship VAF.

Those photos are scary

That part failing in flight would be a way to ruin your whole day.

Luckily, as you found out the fix is simple and cheap.

Good catch.
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  #4  
Old 06-06-2012, 01:17 AM
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bruceh bruceh is offline
 
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Default

The elongated holes come that way from Van's.
Here's what mine looked like during the fitting to the fuselage.



I'm not sure why Van's does the elongation of the holes to this part, since you have to drill the forward spar in the VS to set the position and angle of the VS rear spar to be straight up and down. Makes me wonder if there should be washers under the bolt heads on the enlongated holes to provide better clamping pressure on the bracket.
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  #5  
Old 06-06-2012, 08:35 AM
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agirard7a agirard7a is offline
 
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Default Washers under bolts

"Washers under bolts". My thoughts exactly.
Especially that from the photo, it appears the crack
radiates from the corner of the bolt. I will be sure to polish
Up that elongated hole well.
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  #6  
Old 06-06-2012, 08:50 AM
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agirard7a agirard7a is offline
 
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Default Elongated hole

It seems from a design standpoint, the only
Reason for an elongated hole would be to
Compensate for shim variation (under the HS mounting brackets)
from what is specified as 1/8" stock. Shouldn't those holes be undersized, non
Elongated and matched in the assembly? Is Vans allowing
For an additional, if needed shim to trim out the horizontal axis of the
Plane? I have seen photos and read reports of the elevators
Having to be in a down position relative to the angle of the HS in order
To achieve level flight.
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  #7  
Old 06-06-2012, 09:05 AM
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GAHco GAHco is offline
 
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Default Metal Bent?

Did I detect the metal having been bent a bit back and forth at the elongated hole?

New part carefully fit and installed you'll be fine!
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  #8  
Old 06-06-2012, 09:08 AM
BillC BillC is offline
 
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Default

Thanks for the info Rob,
Since it's an easy place to look I'll be inspecting this weekend. As a reminder, The same vertical stab is also used on the 7's so it would probable be a good idea to post something over there or in the general section just in case they don't see it here.
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  #9  
Old 06-06-2012, 09:49 AM
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Av8torTom Av8torTom is offline
 
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Default Can't tell

from the photos, but it looks like there is a fair amount of surface corrosion in that area. Was is primed?
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  #10  
Old 06-06-2012, 09:49 AM
Rob's RV9A Rob's RV9A is offline
 
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Default F-981

Thanks to all for your comments. Thanks to BILLC suggestion, I will post in the 7 Forum.

The crack extends left and right of the bolthole. Looking at the drawings, the drawing hole appears to be elongated. All four-bolt holes on the plate have bolt score marks from being fastened in place at the lowest point of the elongated hole. For the cracking occurrence to me it is difficult to pin a cause, i.e. too much torque, not enough torque, non burred hole, or defect on original and subsequent installation and adjustment, too much weight for a few moments on the one hole, washer placement, etc. I am not an engineer; my conclusions are just guessstimates. If anyone else or Van’s has previous experience with this fault would be good to know.

However, the fix is a simple repair; just time consuming.

In response to GAHco attached is another wider view of the F-981crack.


http://s1254.photobucket.com/albums/hh616/RV9aer/
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