dougweil
Well Known Member
My RV-7 has been a great machine over the last 4 years. 99.9% of the 450 hours thus logged have been pretty much trouble free. But here?s a short story of a ?gotcha? that popped up recently. It was not a real big deal and probably not a major safety of flight item, but I?ll pass this along anyway.
I have an Aerosport IO-375 installed with a standard Precision Silver Hawk fuel injection system. On a recent run-up prior to takeoff, the vernier mixture control seemed to have a ?sticky? spot as I pushed the mixture to full rich. I experimented a little and it seemed like the vernier control was hanging up about an inch out from full rich. So like a dummy, I took off anyway assuming that I might have to look into it later.
I headed over to a local airport to run through a practice GPS approach. I had leaned out the mixture to my usual 8 gph and didn?t think too much about it until I ran through the approach and landing checklist and pushed the mixture to full rich. Except it wouldn?t move! I got a little more forceful but it was ?frozen." All was running normal but I decided that maybe I shouldn?t mess with it any more and headed back home.
In the hangar I really thought that the vernier control was bad but after removing the cowl I found the culprit.
There is a screw on the LHS of the fuel servo that serves as a stop for full rich and idle cutoff for the mixture control. It was loose and about to fall out and was blocking the mixture control arm from moving to the full rich position. This screw had a drilled head but had never been safetied. I guess it came this way from the factory and I had never thought to physically check it. And of course I had inspected the fuel servo many times but never questioned why this was the only screw that was not safetied. I screwed it back in and safety wired it such that it would not loosen up again and all was back to normal.
Notice the small screw with the white nylon collar next to the mixture arm. It has back out blocking movement of mixture control.
It's pretty easy here to see how the screw has backed out.
A simple safety wire job and that should not happen again!!!
I have an Aerosport IO-375 installed with a standard Precision Silver Hawk fuel injection system. On a recent run-up prior to takeoff, the vernier mixture control seemed to have a ?sticky? spot as I pushed the mixture to full rich. I experimented a little and it seemed like the vernier control was hanging up about an inch out from full rich. So like a dummy, I took off anyway assuming that I might have to look into it later.
I headed over to a local airport to run through a practice GPS approach. I had leaned out the mixture to my usual 8 gph and didn?t think too much about it until I ran through the approach and landing checklist and pushed the mixture to full rich. Except it wouldn?t move! I got a little more forceful but it was ?frozen." All was running normal but I decided that maybe I shouldn?t mess with it any more and headed back home.
In the hangar I really thought that the vernier control was bad but after removing the cowl I found the culprit.
There is a screw on the LHS of the fuel servo that serves as a stop for full rich and idle cutoff for the mixture control. It was loose and about to fall out and was blocking the mixture control arm from moving to the full rich position. This screw had a drilled head but had never been safetied. I guess it came this way from the factory and I had never thought to physically check it. And of course I had inspected the fuel servo many times but never questioned why this was the only screw that was not safetied. I screwed it back in and safety wired it such that it would not loosen up again and all was back to normal.
Notice the small screw with the white nylon collar next to the mixture arm. It has back out blocking movement of mixture control.
It's pretty easy here to see how the screw has backed out.
A simple safety wire job and that should not happen again!!!