Fuel Tanks - Two Steps Forward, Three Steps Backward
Sunday, February 26 2006 @ 08:36 PM PST
Contributed by: Kevin Horton
It's been two steps forward, and three steps back with the fuel tank leak fixing. Last weekend I put some Proseal inside a corner of the left fuel tank to hopefully fix a leak. It's a week later, the Proseal is cured, so I started a leak check yesterday. It is hard to say for sure, as the level in the manometer goes up and down with the temperature and atmospheric pressure, but there certainly isn't a large leak. I'm hopeful.
But the bad news is that on Thursday Van' Aircraft released Mandatory Service Bulletin (SB) 06-2-23, which "requires" RV owners to open up the fuel tanks to add safety wire to the fuel pickups. It was triggered by a fuel pickup that became undone inside a fuel tank, resulting in fuel starvation and an off-field landing. After Van released the Service Bulletin, another builder reported that the same thing had happened to him, but he was able to glide to an airfield. So, with two known incidents, I agree that it is wise to secure the fuel pickups so they cannot unscrew. I'll have to open both fuel tanks up to do this, so that'll mean yet another round of leak checks. The leak check I'm doing now is still useful, as I need to know whether the repair I did last week is working.
SB 06-2-23 "requires" the owner to remove the fuel pickups, drill a small hole in each securing nut, and to use safety wire to secure the nut after tightening it. This is easy enough to do with the normal fuel pickup, but it is a much bigger job if you have an inverted fuel pickup (as I do in the left wing). The normal fuel pickup is mounted on the access cover on the inboard end of the fuel tank, so you it comes out of the tank with the access cover. But the inverted fuel pickup screws onto to an elbow way up in the very front of the fuel tank. It would be pretty much impossible to get safety wire on it, working through the access cover near the back of the tank. So, Van recommends that the elbow be removed so the safety wiring can be done on the bench. But, this means that you need to somehow scrape off the Proseal that keeps it from leaking around the elbow, then put some new Proseal in place after reinstalling the elbow. That looks like a leak waiting to happen.
I'm planning an alternate means of compliance with the SB. I'm going to spread some Proseal on the nut that secures the inverted fuel pickup to the elbow, after making sure the nut is properly tightened. There is no way that nut will come loose if I put a good layer of Proseal on it and the elbow. The inverted fuel hose I've got now is made from a type of hose that is supposed to be replaced every few years. I'll order a length of Teflon lined flexible hose, as it has a supposedly infinite service life. - I've learned that the Teflon hoses are quite a bit stiffer than conventional hoses, and it is quite possible that they are too stiff to work properly as an inverted fuel pickup. I will not order a Teflon hose for this application.
Update - 28 Feb 06 - Another builder has stepped forward to say that he totaled his RV several years ago after the fuel pickup came undone, so we are up to three known events.