Light Aircraft Association

I was surprised to find that the Facet pump will not free flow when switched off. It will when even the slightest suction is applied, even sucking by mouth, but remove the suction and the flow stops. This is with the fuel tank a foot above the pump. As many aircraft are fitted with them, pesumably this is acceptable. Any advice?

Off topic a little but I know from experiance that even a high wing Rotax plane will not have enough fuel pressure to gravety feed at full power in case of the mechanical pump going belly up. On a Technam P92 I by passed the mechanical fuel pump and tried to use only gravety but only got to 3500 rpm so you need some form of pump.
Does the facet allow a head of fuel to run through? What type of facet did it have an anti syphone valve? The 40105 I have here indeed needs a little "push " to get fuel flowing , but I am sure a gravety feed system would work with this installed.
So only a problem if you loose both the mechanical and electric really is the answer to the .

Kevin

Easy fix is to by-pass the inlet to the Facet pump and fit a non-return valve. You'll find that the EDP could (will) cavitate, if you don't fit the by-pass.

Thanks, Sandy. I'm doing that.

There are different models of facet pumps, the Glastar Sportsman has two main tanks and two auxilary tanks a facet pump is used to transfer fuel from aux to main but the pump allows no flow until it is powered up, so you can control fuel flow.

Might be worth checking what model is fitted.

Ian

It's the Square type of pump I assumed Jim to have as I've seen this problem and solved it as described.

Are you saying that you can't transfer fuel from Aux to Main without that pump functioning on your Glastar?

Yes thats correct, you run the mains down then transfer with pump from aux tanks

Not done it yet as still building!!!

Ian

Sorry Ian but that doesn't seem like a good idea to me in the event of transfer pump failure. I'd want some method of getting to that fuel in the event of the mains running down too far. Maybe I'm missing something though. ?

The method is to only run the mains down to half then top up from aux tanks, you have two aux tanks and two pumps so there is a measure of redundancy. But yes you are relying on the pump to get at that fuel.

Ian

Ok Ian but I still wouldn't be happy with that situation as an Inspector. IIRC, the Glastar has some Header tanks down the rear door posts. What about a by-pass with a NRV between the pump inlet and the pipe into the header tank? That way you get to the fuel in the event of pump failure and you can still transfer fuel with the pump , Aux to Main as you described.

Talk to your own Inspector or Engineering about this first.

Yes that sounds possible, certainly worth looking into, but there is I think about ten Glastars operating in the UK and hundreds worldwide with this system. However I see your point failure of an electric pump, wire, fuse, breaker etc. could leave you unable to access fuel.

Ian

These Facet pumps on LAS free flow according to the description

http://www.lasaero.com/site/products/ar ... =F01TOTXXH

I have one of these fitted to my Minicab and I recently happily drained over 30 litres of fuel out of the gascalotor with the in-line pump off and it flowed at quite a rate, no suction necessary.

Phil