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  #1  
Old 03-21-2016, 06:03 PM
dougweil's Avatar
dougweil dougweil is online now
 
Join Date: Jun 2005
Location: Hudson, WI
Posts: 260
Default Silver Hawk fuel injection servo "gotcha"

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!!!
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Hudson, WI
president, Twin Cities RV Builders Group
RV-4, sold
RV-7 completed and flying N722DW, 930 hours
Based Lake Elmo, MN (21D)
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  #2  
Old 03-21-2016, 06:14 PM
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RV7A Flyer RV7A Flyer is online now
 
Join Date: Jul 2013
Location: US
Posts: 2,528
Default

Thanks for making me go dig through all the pictures of my engine installation

Yep, safety wire is there...whew! Add another thing to the annual inspection checklist...

Good save on your part, glad it didn't result in a much more serious problem.
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  #3  
Old 03-21-2016, 06:49 PM
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JonJay JonJay is offline
 
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Thanks for posting. Mine is also ok.
Being a little bit picky, you should safety to the opposite or lower flat of the large plug. This would allow no loosening or counter rotation.
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  #4  
Old 03-22-2016, 09:34 AM
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airguy airguy is offline
 
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Location: Garden City, Tx
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Quote:
Originally Posted by RV7A Flyer View Post
Thanks for making me go dig through all the pictures of my engine installation

Yep, safety wire is there...whew! Add another thing to the annual inspection checklist...

Good save on your part, glad it didn't result in a much more serious problem.
Just did the same thing, mine is good as well. Good catch!
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Greg Niehues - SEL, IFR, Repairman Cert.
Garden City, TX VAF 2021 dues paid
N16GN flying 900 hrs and counting; IO360, SDS, WWRV200, Dynon HDX, IFD440, G5
Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
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  #5  
Old 03-22-2016, 12:03 PM
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dougweil dougweil is online now
 
Join Date: Jun 2005
Location: Hudson, WI
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Thanks for the safety wire suggestion Jon. Me and safety wire never get along!! I'll correct it next time I have the cowling off.
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Doug Weiler

Hudson, WI
president, Twin Cities RV Builders Group
RV-4, sold
RV-7 completed and flying N722DW, 930 hours
Based Lake Elmo, MN (21D)
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  #6  
Old 03-22-2016, 08:13 PM
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kevinsrv7.com kevinsrv7.com is offline
 
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Posts: 165
Default Thanks

Thanks Doug for the heads up!
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  #7  
Old 03-22-2016, 08:23 PM
RV Jerry RV Jerry is offline
 
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Location: Chino, CA
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The safety wire that is attached to plug appears to be on the loosening side
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  #8  
Old 03-22-2016, 08:48 PM
Speeddog7 Speeddog7 is offline
 
Join Date: Apr 2010
Location: Plano, Texas
Posts: 42
Default It's safe for now, so go easy on him.

Quote:
Originally Posted by RV Jerry View Post
The safety wire that is attached to plug appears to be on the loosening side
Guys, please note that the original safety wire for the plug is still in-tact and correct. Yes, technically, the newly added safety wire should be attached to the other side of the plug fitting, but it'll be just fine till the next time he removes the cowl.
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  #9  
Old 03-22-2016, 09:29 PM
RV Jerry RV Jerry is offline
 
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Sorry , I did not see the safety wire on the other side I didn't mean to pick on you so I will keep quiet from now on
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  #10  
Old 03-23-2016, 08:45 AM
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JonJay JonJay is offline
 
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Quote:
Originally Posted by RV Jerry View Post
Sorry , I did not see the safety wire on the other side I didn't mean to pick on you so I will keep quiet from now on
I don't think the OP minds. Speaking for myself, you may pick on me anytime you see something that might be amiss, even if it isn't.
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RV1 - Proud Pilot.
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