Using check valve in YS 140DZ fuel system

[Earl Haury]

Peter

Using a check valve works, but there is a potential for problems with 
thermal expansion when the temperature of the fuel in the tank rises (as 
when the aircraft is exposed to sun for a while after fueling). This 
pressure increase can be quite significant and can damage the check valve, 
flood the engine, etc.

Instead of a check valve, use an aluminum tubing "loop", exterior to the 
tank, in the vent line. Simply route it to behind the tank so that the "top" 
of the loop is above the fuel when the nose of the aircraft is pointed down. 
No gross fuel spillage will occur and yet thermal expansion is relieved.

I've used bladder tanks, check valves, and even pipe pressure successfully 
with the DZ, but the "loop vent" is my preference.

Earl
----- Original Message ----- 
From: "Peter Pennisi" <pentagon.systems at bigpond.com>
To: <discussion at nsrca.org>
Sent: Monday, August 30, 2004 6:08 AM
Subject: Using check valve in YS 140DZ fuel system


>
>
> Some flying buddies of mine have been having a discussion about using a
> check-valve in the fuel system to essentially stop fuel from dripping out 
> of
> the vent line. I have been using this system without any problems that I
> know off for some time. One of the pattern flyers I fly with is very good
> with engines and he doesn't think it is a very good idea to use the valve 
> in
> the DZ fuel system as the tank will always have a slight pressure build up
> inside which may result in inconsistent engine runs. I don't know about 
> his
> theory but I do know that all the Japanese flyers at the recent CAOCC 
> event
> were using check valves in the fuel system.
>
> I would be interested to hear from anyone who may have an opinion on this
> subject.
>
>
> Regards,
>
> Peter
>
>
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