Further to my posting of yesterday on this same subject, I have looked at the Andair website (www.andair.co.uk). Andair makes two check valves. One of conventional design and a similar one with a pair of small holes drilled through the internal shuttle. The latter is the one intended for use in fuel tank vent lines. The stated purpose of the two holes is to prevent overpressurization of the fuel tank due to thermal expansion of the fuel while the plane is parked. They don't make any mention of the problem that I alluded to in my posting, namely, the need to vent the tank during climb and I question whether or not "two small holes" are adequate to do the job. Assuming these two small holes are adequate to prevent thermal overpressurization, I have to wonder if the check valve actually does any good. In other words, does it pass a similar amount of fuel as would be passed if the check valve weren't there, just more slowly? Wouldn't you be better off without the check valve and avoid all the failure modes associated with either pluggage of the two holes or failure of the check valve to open?

At the conclusion of my previous posting, I included a PS suggesting that a float valve might make more sense than a check valve. In doing so, I hadn't considered the thermal expansion issue. On that basis I retract that suggestion. More than ever, I think I will fly naked (i.e., nothing in the vent line) and just make a point of flying coordinated and parking on the level.

Jim McKibbin