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Flap Pushrod Wear

A

AN23

Well Known Member
As my first act as a new A&P and the owner of a RV-7 that I didn't build, I decided to move my condition inspection back to December from the original February timeframe to get it done when the temperature inside the hangar was more tolerable. As part of the inspection, I decided to replace the standard aluminum tube flap pushrods with the RV-9 style hexagonal rods. Upon removal of the first pushrod, I was surprised to find that the rod had been touching the fuselage skin and had lost almost 30% of the tube wall material! The wear area was on the forward side of the rod and was not easily seen without removing the rod as the wear area was relatively small and covered by the fuselage skin when the flaps were down. The other side turned out to have exactly the same wear pattern and loss of material. When static, it appeared that there was clearance when the flaps are down but flight loads were obviously closing up that clearance and causing rubbing. Thirty minutes with a file had both holes opened up. I'd like to suggest that everyone, please, please take a close look at your pushrods.
 
74-07 said:
As my first act as a new A&P and the owner of a RV-7 that I didn't build, I decided to move my condition inspection back to December from the original February timeframe to get it done when the temperature inside the hangar was more tolerable. As part of the inspection, I decided to replace the standard aluminum tube flap pushrods with the RV-9 style hexagonal rods. Upon removal of the first pushrod, I was surprised to find that the rod had been touching the fuselage skin and had lost almost 30% of the tube wall material! The wear area was on the forward side of the rod and was not easily seen without removing the rod as the wear area was relatively small and covered by the fuselage skin when the flaps were down. The other side turned out to have exactly the same wear pattern and loss of material. When static, it appeared that there was clearance when the flaps are down but flight loads were obviously closing up that clearance and causing rubbing. Thirty minutes with a file had both holes opened up. I'd like to suggest that everyone, please, please take a close look at your pushrods.
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Congratulations on find the problem. However your reasoning doesn't quite make sense. Flight loads will push the flaps toward the "up" position, and should have the same effect as retracting the flaps.
 
I agree Mel. All I can say is that when static, the rods JUST cleared the fuselage skin but something has caused the wear.
 
Wear

74-07 said:
As my first act as a new A&P and the owner of a RV-7 that I didn't build, I decided to move my condition inspection back to December from the original February timeframe to get it done when the temperature inside the hangar was more tolerable. As part of the inspection, I decided to replace the standard aluminum tube flap pushrods with the RV-9 style hexagonal rods. Upon removal of the first pushrod, I was surprised to find that the rod had been touching the fuselage skin and had lost almost 30% of the tube wall material! The wear area was on the forward side of the rod and was not easily seen without removing the rod as the wear area was relatively small and covered by the fuselage skin when the flaps were down. The other side turned out to have exactly the same wear pattern and loss of material. When static, it appeared that there was clearance when the flaps are down but flight loads were obviously closing up that clearance and causing rubbing. Thirty minutes with a file had both holes opened up. I'd like to suggest that everyone, please, please take a close look at your pushrods.
Click to expand...

I would check to see how the other end of the rods are connected to the flap weldment inside the fuselage. Perhaps there are washers on the bolt there that holds the pushrod to close the the skin. Possibly by re-arranging the washers you'll get better clearance.
 
I'm now thinking perhaps when new, the rod did not have sufficient clearance and thru the next 375 hours of flight time, it "adjusted" either the flap rod, the fuselage skin, or both. Either way, it has plenty of clearance now and new pushrods!
 
I also read here that more than one RV has been found with no aft spar bolts installed. :eek:
 
74-07 said:
As my first act as a new A&P and the owner of a RV-7 that I didn't build, I decided to move my condition inspection back to December from the original February timeframe to get it done when the temperature inside the hangar was more tolerable. As part of the inspection, I decided to replace the standard aluminum tube flap pushrods with the RV-9 style hexagonal rods. Upon removal of the first pushrod, I was surprised to find that the rod had been touching the fuselage skin and had lost almost 30% of the tube wall material!
Click to expand...

What you have discovered is likely the cause of any flap pushrod that has ever failed (Mechanism not built correctly).
The standard pushrod is more than strong enough.... just make sure it is not being damaged.
Changing to the hex pushrod will require that you enlarge the opening a lot if it wasn't even big enough for the standard one.
 
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