azcloudflyer
Active Member
At about 28 hrs into Phase I flight testing, I noticed that I was dripping fuel from the right wing fuel tank vent. It was too consistent of a drip to be anything but a leak. The leak was coming directly out of the vent, not around it. The RV-10 vent system runs the vent pipe from the high side of the tank, through the fuel, to a bulkhead fitting at the lower inboard end of the tank. This fitting is submerged in fuel whenever the tank has 22 gallons or more of fuel. Within the wing root, there is just a pipe that you add to exit to the bottom of the wing and complete the vent system. I've concluded that the leak is at the flared tube to bulkhead fitting inside the tank. This fitting is not accessible once the tank is completely riveted together.
There is a 1.5" diameter hole for the fuel sender located about 3.7" away from the vent bulkhead fitting which is shown in the first photo. You can just barely touch the internal nut with your middle finger from this hole. My first step in developing a tool to go in the hole and turn the nut was to make a mock up of the fuel sender hole and vent position. The mock up is in the second photo below. Then with another engineer's expert help, we developed a tool that could go in the hole and swing far enough past the hole in each direction to turn the nut. You have to be able to swing the wrench far enough so that it can be repositioned back enough to pick up another flat of the nut. I was able to practice placing the tool on the nut using the mock up.
I flew off the right fuel tank as far as I could in flight. Then on the ground I transferred the remaining fuel from the right to left tank. I was able to go in and tighten the nut at least one and a half flats of the nut. It seemed pretty tight to me so I reinstalled the fuel float sensor, buttoned everything up and filled the tank with fuel. I wish the story ended here but the fitting continued to leak. It has slowed but the vent was still wet to the touch at the output end.
I decided to give it another try, so I flew off the fuel, transferred remaining fuel, removed all the cover panels and the fuel float sensor and tightened the fitting as much as I could using the tool. It seems really tight to me now and I don't think going any tighter could possibly be productive. Well it looks like that did the trick. It has stopped leaking. yeah! If this doesn't hold up I plan on removing the tank, capping the existing vent, and installing a new always dry vent at the outboard end of the tank. There is almost 2" of room between the outboard end of the tank and the next wing rib to add a bulkhead 90 degree fitting and vent tube there.
So my reason for posting this, besides relating my tale of woe, was to offer the use of this tool to anyone else that may discover the same problem with their quick build wing. But from my research in the archive this doesn't appear to be a common problem.
Back to flight testing.......
View of fuel tank rib
Mock up of rib
The right Tool for the job
Internal fuel tank view of tool in use
There is a 1.5" diameter hole for the fuel sender located about 3.7" away from the vent bulkhead fitting which is shown in the first photo. You can just barely touch the internal nut with your middle finger from this hole. My first step in developing a tool to go in the hole and turn the nut was to make a mock up of the fuel sender hole and vent position. The mock up is in the second photo below. Then with another engineer's expert help, we developed a tool that could go in the hole and swing far enough past the hole in each direction to turn the nut. You have to be able to swing the wrench far enough so that it can be repositioned back enough to pick up another flat of the nut. I was able to practice placing the tool on the nut using the mock up.
I flew off the right fuel tank as far as I could in flight. Then on the ground I transferred the remaining fuel from the right to left tank. I was able to go in and tighten the nut at least one and a half flats of the nut. It seemed pretty tight to me so I reinstalled the fuel float sensor, buttoned everything up and filled the tank with fuel. I wish the story ended here but the fitting continued to leak. It has slowed but the vent was still wet to the touch at the output end.
I decided to give it another try, so I flew off the fuel, transferred remaining fuel, removed all the cover panels and the fuel float sensor and tightened the fitting as much as I could using the tool. It seems really tight to me now and I don't think going any tighter could possibly be productive. Well it looks like that did the trick. It has stopped leaking. yeah! If this doesn't hold up I plan on removing the tank, capping the existing vent, and installing a new always dry vent at the outboard end of the tank. There is almost 2" of room between the outboard end of the tank and the next wing rib to add a bulkhead 90 degree fitting and vent tube there.
So my reason for posting this, besides relating my tale of woe, was to offer the use of this tool to anyone else that may discover the same problem with their quick build wing. But from my research in the archive this doesn't appear to be a common problem.
Back to flight testing.......
View of fuel tank rib
Mock up of rib
The right Tool for the job
Internal fuel tank view of tool in use