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  #11  
Old 06-13-2016, 08:11 AM
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Saville Saville is offline
 
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Location: KBVY Massachusetts
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Just this weekend I positively determined that the B nut on the left fuel tank air vent - on the inside of the tank - was so loose I could tighten it with my fingers.

Don't know if it's been that way or got that way or, if it got that way how it got that way.

But it happens.

Now I have to tighten it and figure out how many turns (or facets) past finger tight I need to go. I have to get it right because I DO NOT want to go through the thrills of removing an access plate again if I can avoid it.

And you can bet I'm going to have other "eyes" (fingers actually) checking it out.

Somehow these things happen and you have to pay attention to every little oddity you run across while flying or maintaining the airplane.
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Last edited by Saville : 06-13-2016 at 10:49 AM.
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  #12  
Old 06-13-2016, 09:45 AM
Rupester Rupester is offline
 
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Location: Mahomet, Illinois
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Quote:
Originally Posted by Kyle Boatright View Post
It isn't just construction, it is maintenance as well. I completed the FWF portion of my condition inspection yesterday and managed to bungle the timing process on the PMag once, and when I corrected it and buttoned up everything, I realized I had to de-cowl again to reattach the MP line. It was like a Three Stooges episode....
Thanks, Kyle! Your confession did me good .... I thought I was only one who made those kinds of "omissions". Some days I'm REALLY glad no one is around to observe my re-dos"
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  #13  
Old 06-13-2016, 10:39 AM
rightrudder rightrudder is offline
 
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Location: Laguna Hills, CA
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This isn't fuel system-related, but early on in Phase 1 I was getting sketchy CHT readings on one cylinder. So I unbundled the wires, checked the connections and, sure enough, found the problem. Although I was POSITIVE I had crimped all the connectors, there was one wire just rattling around in an uncrimped barrel, making intermittent contact. At least it was an easy fix....20 seconds with some crimping pliers.

It happens, despite our best efforts.
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RV-9A "slider"--sold in July 2021
Flew to Osh in 2017, 2018 & 2019!
Donation made for 2021
You haven't seen a tree until you've seen its shadow from the sky -- Amelia Earhart
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  #14  
Old 06-14-2016, 09:51 AM
Breezy Breezy is offline
 
Join Date: Nov 2011
Location: Okeana, Ohio
Posts: 113
Default B Nut Loosening

I have encountered loose B nuts on a number of fuel systems and locations on RVs.
I am finishing the build on a second RV-8 that included wings purchased from others. For differing reasons during the builds I removed the access panel to the fuel tanks. While doing a general look around found the B nuts on fuel pick ups only finger tight. This included fixed tubes and flop tubes. On the flop tube every fitting was loose from the attachment at the bulkhead fitting to the brass end. This has me thinking Vans may need to have a more robust reminder to tighten these fittings prior to closing the tank.
I have also encountered an issue on another RV-8 that was a QB kit. The customer had fuel streaming from the vent while parked. The problem was the B nut for the internal vent line was not attached to the bulkhead fitting at the inboard tank rib. If topped off a siphon would start and continue till the fuel level drained below the fitting. This left a very large pool of fuel on the hangar floor. The aircraft had 4-500 hrs so either the nut was not torqued properly or there is some mysterious vibration that is loosening these nuts. My money is on improper torquing.
Prior to a final closing of your fuel tanks or if doing some other repair take time to recheck-rechecking these fittings. Another level might be to consider a dab of ProSeal on the nut after torquing to stake it in place.
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First offense RV-8; N594WR; 80594 (time served)
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Repeat Offender: 83137 (Flying 10/16)
N837DW; Superior IO 360; G3X Touch.
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One More Time: 140359, -14 in process, IO-390 (Maybe)


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  #15  
Old 06-14-2016, 10:07 AM
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Saville Saville is offline
 
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Quote:
Originally Posted by Breezy View Post
The aircraft had 4-500 hrs so either the nut was not torqued properly or there is some mysterious vibration that is loosening these nuts. My money is on improper torquing.
And what is the proper torquing?

thanks!
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  #16  
Old 06-15-2016, 07:02 AM
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bret bret is offline
 
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One problem if you are tightening a hose is to use three wrenches, one to keep the opposing Tq off the fitting, one to keep the (hose) from turning, and one for the B nut. I Also notice on the aluminum fittings, they loosen up easier compared to the torque you apply when tightening?
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  #17  
Old 06-15-2016, 07:32 AM
BillL BillL is offline
 
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Location: Central IL
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Quote:
Originally Posted by Saville View Post
And what is the proper torquing?

thanks!
Use the Vans table for torque for 3003 al lines. Here is a thread that covers the topic in depth. Read the whole thread for content, the good information is scattered through there. There are experiments and validation.

http://www.vansairforce.com/communit...ghlight=torque

Definitely DO NOT use higher torque than nominal in the table. There is a bid difference between dry and lubed in tube deformation, and it is insanely easy to get lube on that flare. If you use a drop when flaring, and just wipe with a dry towel, it still has lube there.
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  #18  
Old 06-15-2016, 08:42 AM
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Saville Saville is offline
 
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Quote:
Originally Posted by BillL View Post
Use the Vans table for torque for 3003 al lines. Here is a thread that covers the topic in depth. Read the whole thread for content, the good information is scattered through there. There are experiments and validation.

http://www.vansairforce.com/communit...ghlight=torque

Definitely DO NOT use higher torque than nominal in the table. There is a bid difference between dry and lubed in tube deformation, and it is insanely easy to get lube on that flare. If you use a drop when flaring, and just wipe with a dry towel, it still has lube there.
That is a great thread. Thank you for supplying the pointer.
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  #19  
Old 06-15-2016, 11:57 AM
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rzbill rzbill is offline
 
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As a reminder to myself, I did a couple of things during the build.

Maybe this is same as most everyone else. It helped me.

1) I used torque seal to mark fasteners and fluid connectors that were 100% "finished". (Note: I agree with Walt about not relying on that paint as an indicator at annual. Many fasteners had "settled in" and needed a few flats to regain torque values at annual)

2) On the incomplete connections that could more likely kill me, I put flags of various sorts such as red tags wired on or a big flag of blue painters tape.

There were many structural fasteners that could go together permanently early in construction. They were easy of course. However, that final year of construction saw a huge amount of off-on/in-out/cut to fit/paint to match activity and I had to be very fastidious about fastener/connector marking.

Added to that, as has been said above, have an inspection party with the local EAA or allow any visitors with a modicum of aviation knowledge to look over your plane frequently as you get towards the end.
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  #20  
Old 06-16-2016, 09:34 AM
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airguy airguy is offline
 
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I went and got my pitot/static check done on Friday, had to chase a small static leak, and found my fitting where the static line goes into my Dynon ADAHRS to be only finger tight. Fixed that, checked the others, and sure enough the pitot and AOA were also just finger tight.
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Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
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