Bill,
If you didn't open or modify the andair check valve, it should still have the obvious arrow on it. Arrow should point inward from the vent to the tank.
The check valve will still allow air or fuel to pass in an outward direction, just more slowly than in the inward direction.
In the attached picture, the outflow path is the two small holes in that next to the bottom grey piece.
If you have the valve out of the airplane, you can blow in easily in the arrow direction. In the opposite direction it's about like blowing up a balloon, maybe a little easier.
The bad news is that you can't make those out holes smaller. I did the math for a IVP climbing to 20,000 @2000 fpm with an empty 50 gal tank and determined that the outflow rate would not be fast enough to neutralize the pressure buildup inside the tank. Therefore I about doubled the diameter of those two holes.
On May 31, 2012, at 1:09 PM, Bill Bradburry wrote:
Thanks, Steve.
That is what I expected should happen. I sent an email to Andair a couple of days ago but no response so far. I was asking them for ways to test the check valves in place. They are not the easiest thing to access to remove. I plan to try to test them today. Probably a vacuum cleaner with the fuel caps off?? I want to be careful about pressurizing the tanks. That is why I hoped to hear from Andair…
Bill B
From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Steve Colwell
Sent: Thursday, May 31, 2012 8:07 AM
To: lml@lancaironline.net
Subject: [LML] Fuel vent check valves
Bill,
Not normal! You should be able to carry 32 gal. per side without venting. Is your fuel system per the plans from wing tanks to the engine? Are the vents modified in any way? Early on I switched from the stock Plastic fuel caps to the optional Key Locking Aluminum Top Caps and that solved a venting problem (out of the caps) for me. Are you sure the Andair fuel vent valves in the wing tips are in correctly?
Steve Colwell Legacy IO-550
I am still getting what I consider a lot of fuel coming out of the fuel vents on my Legacy. I no longer put more than about 20 gal in each tank but I am still getting leakage from the vents.
Is this normal? What should I check and how should I go about it?
Bill B