Fuel Drain Plug failure Aerotrike Scout

[Biggles]

I was doing a though check of the microlight yesterday. I changed the fuel filter and when I cut it open i found 1mm flakes of rubber. (and a piece of red plastic from my fuel container). The rubber concerned me as I have recently changed out all the fuel lines for new and the rubber flakes looked like perished rubber. I also drained the fuel tank and half way through that exercise the drain plug stopped sealing when I changed container. After the fuel was drained I found the rubber o-ring of the drain plug was in the bottom of the tank. I fished it out and it was barely a ring anymore and disintegrated in my hand. The warning sign of this was that the drainplug had a drip previously, but a twist of the plug solved that, so i was not too concerned.

I dread to think what could have happened if the rubber o-ring failed or came adrift in the air.

Anyway, anyone know where I can get a replacement drainplug with thread to fit the fuel tanks of an Aeroktrike Scout? I will contact Aerotrike tomorrow.

[nicow]

Rainbow-Aerotrike is the best place to buy it from.

[HENNING JOHAN]

I've got the old tank on my scout!I had the same problem 3 years ago with the fuel drain plug.At the end aerotrike replace it with a cobra drain plug.Walter or Mike will sort it out for you!

[Bundy]

Can anyone give me a logical reason why aircraft have this type of valve?

A simple ball valve would serve exactly the same purpose and would not be prone to leaking or washer failure/perishing? Why do we have these silly spring loaded seal setups? Just as easy to open a ball valve and do a fuel test...

Be much easier to drain the tank too when necessary...

Just asking.

[Bulletjie]

Can anyone give me a logical reason why aircraft have this type of valve?

A simple ball valve would serve exactly the same purpose and would not be prone to leaking or washer failure/perishing? Why do we have these silly spring loaded seal setups? Just as easy to open a ball valve and do a fuel test...

Be much easier to drain the tank too when necessary...

Just asking.

Would also like to know.

[Turbo]

its common, i have just had two new ones installed by walter and mike - and they leaking.... dont use their units, the O-ring is either too large or grows in the fuel (95 octane has additives in it that attacks certain materials) or the material used is incorrect and does not seal after a while.

The material must be Nitrile, NOT RUBBER! i have a few on order from the USA - ill order about 10 extra in case anyone needs some in future.

[bobthebuilder]

Hi Alan,

A ball valve would be easier to open and close, and thats probably where the problem lies. The standard drain cocks used on most trikes do offer an element of safety. One cannot (well ... shouldn't be able to) open the drain cock accidentally and drain the entire fuel tank.

Nitrile O-rings are probably the way to go as Turbo states.
A higher Nitrile content enhances resistance to fuel and oil but elasticity and resistance to compression is compromised.

As to the supply.... not sure that a special import would be required. Bearing Man Group stocks them. Cheap as chips!

[Bundy]

Hi Alan,

A ball valve would be easier to open and close, and thats probably where the problem lies. The standard drain cocks used on most trikes do offer an element of safety. One cannot (well ... shouldn't be able to) open the drain cock accidentally and drain the entire fuel tank.

Thanks Byron...I guess it does make sense then.

[mulderpm]

Thanks Byron. I have replaced the washer with a Nitrile type from Hudson Rubber in Pretoria. I replaced the O-ring 2 years ago with one from Midas and it still seems to be ok. Don't know if it is Nitrile. I know of one guy from Ingwe that had an engine out because of the in-flight failure of the valve. Check it regularly!

The ball valve sounds like a good idea, but as you said it creates the opportunity for bumping it open. The drain plugs used on our tanks have been chosen for safety reasons and are used on most planes to check for water in the tanks. General aviation practice

[Mc Guyver]

Most times the problem occurs when pilots pull the valve down and turn it to try and get it to seal.
The problem is a bit of dirt not allowing the valve to seat.
All you need to do is let it flush clean and the leak will stop (not much fuel wasted)

[bobthebuilder]

I have read that a chamois can be placed in filler when refuelling. This should get rid of even the finest of debris and possibly even water.

[BUKS VAN NIEKERK]

My 2 cent input,the same leaking fuel cock,replaced the
O ring 3 x still leaking and out of ideas,ian found that the
Brass embedded nut that screw into the plastic tank
was cracked all around, me over tighten the fuel cock
When replacing the cock,ian removed the damaged part
And manufactured a new brass nut that screw into the the
Tank Problem gone,sorry little *+@ o ring

[Turbo]

Thanks Byron, do you know where to get the ball valves?? I want to replace these ASAP.

[bobthebuilder]

Sure!!!!

Aircraft Spruce stocks them.

[Turbo]

purchased -- will take pics of the units when they arrive.

Sadly the US made drains use an imperial thread, and the local ones installed in the Cheetahs are metric -- so no compatability im afraid. Went to Rainbow today and Walter and Mike were kind enough to replace these while i waited --- thanks for the great service once again gents!!