fuel transfer on Turbo Twin Comanche

[Christopher Hufnagel]

After the last long trip in our 1966 Turbo PA30 we fueled the Main tanks and tip tanks, leaving the Aux tanks nearly dry in anticipation of weight issues on the next flight.
On preflight for a local exercise flight, I noticed that the right tip tank was completely empty and the right Aux was full.
Upon adding fuel to the right tip tank the overflow for the right Aux tank began to pour out fuel.
I turned on the electrical power and cycled the tip tank solenoid and moved the fuel selector to the various tanks.
It appears that the dripping from the Aux vent drain has stopped.
Has anyone ever had this experience? How did the fuel get into the Aux tank and where should we tell the mechanic to start looking.
Not sure when this transfer took place, but the 50HR AD on the fuel selector was preformed about two weeks ago.

Thanks for any input,
chris

[N3322G]

Chris,

Check the tip/aux solenoid for correct electrical connection around fuel selector - if it was disturbed during AD or any other work.

Check solenoid for operation - you should be able to hear a click when it is turned on - if not, try cleaning it. Search for other discussions for Krisitn's advice on cleaning.

Let us know how it turns out so we can all learn.

[Christopher Hufnagel]

Thanks, Pat.
I will let the mechanic know. I would suspect something near the selectors, as you have suggested. We have never had any problems and it seem a bit odd that this happened right near the time the AD on the selectors was being completed.
I have looked at fuel schematics but they seem vague to me. Do you have any idea how the fuel would have gotten into the Aux from the lines. I would assume there is a one way valve in there somewhere to prevent such an event.
Will certainly let you know the results!
chris

[md11flyer]

Hi Chris.
Funny thing, I have a 1966 pa-30 as well and last month the same thing happened to me... except for the fact my aux was full when I parked the airplane.
When I returned the 10 gallons that was in the tip was now a blue spot on the hangar floor. My solenoid valve, which for about a year was never used, stuck in the half open position.
I suspect that do to lack of activity the solenoid valve seals , or maybe some small amount of debris in the vavle caused it to stick.

I found this out in the hangar by cycling the valve. At first there was no audible clicking like the other solenoid valve. I gave the solenoid a gentle tick with a plastic mallet and tryed again and
it works perfectly again.
Every flight that I take now I cycle the solenoids and listen for the click to make sure they are working and to keep them moving freely.

The reason the fuel went from the tip to the aux is there are no check valves to prevent this, simply because of the design of this system.
Just imagine 2 lines feeding into 1 line, The solenoid in the "off" position allows the fuel from the aux tank to flow to the strainer. At the same time when the solenoid is in the "off"
position the line from the tip tank is closed by the position of the solenoid shuttle cock. When you energise the solenoid, the shuttle cock moves over to open the tip tank line to the strainer and at the same time
shutting off the line from the aux to the strainer.
Now what happened in most likely both our cases is, the fuel solenoid shuttle cock stuck in the midway position which allowed fuel from the tip to, via, gravity, find its way to the aux tank.
Of course the tip will empty completely as the lowest part of the tank is above the highest part of the aux tank.

For me it was a lot of wasted fuel.. for you just a transfer of fuel from one tank to the other.

Now the above is one scenerio, the other is you have bad seals in the solenoid.. In any case when you cycled the solenoid on the ground and the fuel transfer from the tip to aux stopped it indicates that you are getting movement in the solenoid. I would have your Ai clean out the solenoid and check the seals for good measure as the sticky seals or debris might cause it to stick again at a later date.
All this implies that you have a good 12 volt supply at the solenoid as well as a good ground.

Hope this helps,
Gary

[Christopher Hufnagel]

Thanks for the input Gary; you have given us some good ideas as to why this happened.
The solenoid is working to the best of our knowledge. The audible click can be heard each time it is activated and we tend to use these tanks quite often so stagnation would not be the problem.
Somehow though, I am beginning to suspect that the problem was that it hung up in the middle position.
I placed a pan below the vent last night and this morning there was some fuel from the dripping, but not too much.
I talked to the mechanic today and we are going to do a little test.
I will let you know the outcome.

More to come.... as we check it out.
chris

[Christopher Hufnagel]

A quick update for future reference for others who may see this problem.

We have discovered that the fuel solenoid valve (a Duke valve) is moving as it should and shows no signs of debris.
After cleaning, it is still seeping fluid, so our guess is that the seals are bad and the valve needs to be replaced.

Tuesday, after the holiday, a call will be made to Osborne to inquire further and most likely buy a new valve.

If anyone has any other suggestions, they are always most appreciated.

Thanks for the input to help us out with this one!
chris

[md11flyer]

Chris: Let us know if you are able to buy a seal kit for these valves or if they overhaul them at dukes for a reasonable
price.

Good luck,

Gary

[Christopher Hufnagel]

Hi Gary,

After a discussion with a tech at Osborne I learned that the valves, Dukes Valves, are proprietary.
Dukes manufactures them, and sells the only to JL Osborne.

There are no repair kits or parts for the valves.
There is no official field overhaul and Osborne does not overhaul
They sell replacements, $660.00, and it is a core exchange.
Another person at Osborne told me they throw the old cores away.

They do last a long time, Ours is 35 years old and the other valve is most likely original to the plane as it is the square style.
They are now cylindrical in shape. Osborne sells the conversion kit from the old style to the new round style for around $725.00.
So expensive, but they appear to have very long lives.

chris

[Christopher Hufnagel]

Oh yeah, valves are back ordered until March at this time!

CH

[md11flyer]

Chris:
Thanks for the info. I was afraid that there was no repair option for the valves, well anyway good to hear that new ones are available
when needed, albeit with a 3 month wait.

Gary