shuttle is moved by a small electric coil built into the valve and totally
sealed. A very high quality 5-pin female plug is built into the side of
the valve body and there is a male plug assembly with the unit that has
a "triple lip silicone rubber gasket" which seals the plug as it is connected.
These valves were built to be installed UNDERNEATH an off road vehicle
chassis where they are exposed to the absolute worst environment possible
and keep on ticking. They are really nice units. There are 100ís of thousands
in use and my supplier says that he has never known of one to fail!
One very important characteristic of these valves is that they do not draw continuous electrical current under ANY conditions! When current is applied to the valve to shift the shuttle, the shuttle moves an internal DPST switch inside the valve body, which automatically turns the current off as soon as the shuttle has shifted. That takes about a millisecond. The valves will also still operate on quite low voltage so if you had an electrical system problem, it is very unlikely that you would be unable to operate the valves before you could get the plane on the ground.
I said the plug on the valve was a five pin plug. The operation of the plug only requires 3 pins. The other 2 pins are to use for indicator lights, which indicate what position the valve is in. This is a very nice feature. I put small lights beside the selector switches on my panel. They arenít really necessary; because you can see by the position of the switches themselves what tank you are on. But they kind of satisfy that urge to have "bells and whistles" and other fancy stuff, and they donít cost much!
Now if we apply the same criteria to these valves that we applied to the manual valves earlier, what will we find?
First of all, the accessibility to the pilot is unquestionably no problem at all. This is because the only things that need to be in the cockpit are 3 small DPDT switches, and they can be located right on the instrument panel where the pilot can easily reach them with his left hand without even thinking about
much less twisting or turning or contorting his body or stretching to reach
Then there is the matter of where to locate the valves themselves? I located mine behind the passengerís seat, on the side wall of the fuselage and on the side of the center console there behind the same seat. There is plenty of room for the valves and their plumbing and wiring. This basically gets the fuel out of the cockpit and it eliminates a ton of fittings and plumbing required by the manual valves. It is also MUCH simpler to install and leaves the cockpit less cluttered.
Also, all 3 of these valves weigh LESS than the manual valve and all the plumbing they require.
If I have one criticism of these valves, it would be that they do not have threaded inlets and outlets that you can screw aircraft AN fittings on to. They have regular automotive type hose barbs molded in which means that everything connecting to these valves must be hose connected with hose clamps. This is not a big issue. Itís just that I am an A&P mechanic and I LIKE AN fittings and good old aluminum fuel lines. The rubber fuel lines have served me very well however, and I really have no concern over their use as long as they are inspected regularly and replaced every couple of years.
It is necessary to install 3 of the selector valves. One serves to select between the upper and the lower wings. Another serves to select between the right and left tanks in the upper wing. And the third serves to select between the right and the left tank in the lower wing. The plumbing is very simple. The 2 outlets of the 2 right/left valves feed into the 2 inlet ports of the upper/lower valve. The outlet of the upper/lower valve then sends the fuel to the electric boost pump and on to the engine. Gascolators are placed before these valves so the fuel is strained and water removed before the fuel reaches the valves.
It is for these reasons that I feel that the solenoid valves are the best choice and solve all the problems inherent with the manual system. I might add that I did not originate this idea. We all have Bill Arnold of Deer Park, Washington to thank for this great solution to a very vexing problem.
|GLASS GOOSE GAZETTE * ISSUE #18, April, 2001||
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