Fuel Shutoff Valve

There's more to an extended-range fuel system than just adding tanks.

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The extended handle for the fuel shutoff valve was fabricated from square aluminum tubing and is supported by a bracket attached to the cockpit floor. Note the aluminum tubing connected to the brass “T” fitting ahead of the rudder pedals. These are fuel lines for the auxiliary tanks. The blue/green tubes are brake lines.

The Murphy Maverick that I ordered came with a standard firewall tank that holds 5 gallons of fuel. The engine choices were the Rotax 503 or the 582, which is what I chose. The 582 has a 4-gallon-per-hour burn rate at 80% power, which would leave me with about one hour worth of flight time when you consider warm-up, taxiing, and a reserve. That isn’t much of a ride in my mind, so I purchased the wet-wing option with the kit, which added another 12 gallons, or about 3 hours more of having fun.

The kit called for a single tank to be built in the port wing, which would add roughly another 80 pounds to the pilot’s side. With this setup there was one ball valve shutoff in the cabin for the wing tank and another one on the engine side of the firewall for the firewall tank. I didn’t like the fact that if something was to go wrong, I couldn’t shut off the fuel from the firewall tank, and having to twist backwards would pretty well render the wing tank shutoff inoperative as well. Another quirk of mine was the fuel monitoring of the wing tank, an “eyeglass” inside the cabin. Although used for years in older airplanes, I was not thrilled to have a clear plastic tube filled with gasoline bobbing beside my left eye. After looking at the fuel setup, I decided that some changes were in order.

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Floor bracket with bushing and handle bolt fitted. A riveted piece of tubing acts as an on/off stop for the valve.

The first change was to split the weight difference of the single auxiliary tank and build two half-size fuel cells, one in each wing. I was required to document construction of each fuel cell and keep a log of materials used and all testing I did to ensure safe construction. I backed everything with a set of drawings and a photo journal as well.

The two tanks were hard plumbed using aircraft-grade aluminum tubing inside of the bulkheads beneath the floor into a “T” fitting that exited through the bottom center of the firewall into the engine compartment. The second change was to install one shutoff valve, which is located on the engine side of the firewall, in between the firewall tank fitting and the “T” fitting where the two wing tanks are joined. This allows for one shutoff valve, with the handle located beside my right leg inside the cabin, where it’s very convenient and safe.

Ball shutoff valve with “T” on bottom and 90-degree elbow on top.

I ordered a shutoff valve from a supply company for about $45. When it arrived, I played with it for quite a while when my wife (also a pilot) walked into the shop. I handed it to her and asked her to show me where the off position was and to explain how she could tell. After a short endeavor, she handed it back to me and said, “Send it back; you can do better than that.” That was the end of the conversation, and back it went. I took another look at the original ball valve supplied with the kit and came up with an idea to make it work.

The handle was removed from the unit and its location on the engine side of the firewall was established, placing it in between both fuel outlets approximately three inches above the floor. A one-inch hole was drilled through the firewall, allowing for the protruding “T” of the valve portion to extend through. Then a four-inch square plate was made to fit tightly over the same protruding part of the valve. This secured the valve and made them one unit.

The fuel system as seen from the forward side of the firewall: (A) Out port from firewall tank (B) One-way check valve (C) Gascolator (D) Ball valve in the vertical position (E) “T” fitting connecting firewall tank and wing tanks (F) Ninety-degree elbow connected to “T” fitting inside the cockpit, which branches out to the wing tanks with aluminum tubing.

The wing-tank fitting was hard plumbed with aluminum tubing and pressure fittings to one side of a “T” fitting on the valve (in flow), while the firewall tank fitting was soft plumbed with fuel line and barbed fittings to the other side of the same “T” fitting. The (out flow) side of the valve was then hard plumbed to the gascolator.

To extend the handle I fabricated a fitting out of one-inch square aluminum tubing by drilling a hole through both sides. Then I file finished one hole to fit the diameter of the valve bolt with its flat spot (to prevent it from spinning). The tubing was attached with the original washer and nut. The other hole was filed square to receive a five-eighth-inch piece of square aluminum tubing, which just slipped into place and was cut to length. Finally, I constructed a bracket that fastens to the floor and supports the end of the square tubing with the handle.

Back side of floor bracket with bushing.

A drawing of the bracket on paper showed some issues that were rectified and then measurements were transferred to aluminum sheet, cut, and bent to shape. A bushing was made of thick aluminum plate and fastened on the inside of the bracket with two rivets. A five-sixteenth-inch hole was drilled through the bracket and bushing. A bolt was fitted from the inside with a nut and flat washer, then placed through the bushing and bracket and fitted with a flat washer, the original handle, another flat washer and nut. The bolt had to have a flat spot filed on a portion of the threads to match the handle hole (preventing it from spinning like the valve).

Ball shutoff valve in place through firewall with 1-inch square tubing adaptor fitted.

Installation was simple: One end of the five-eighth-inch tube slipped into the square fitting at the valve, and the other end slipped over the bolt head at the bracket. I aligned the bracket on the floor, drilled the holes, Clecoed it in place, and was done.

To ensure a proper positive detent of where the valve was “on” or “off,” I riveted a quarter-inch long piece of one-eighth-inch tubing onto the face of the bracket with a long SS rivet. There are no issues as to where the “off” position is on my shutoff valve; when the handle is digging into my right leg, the fuel is off, and when it’s down and out of the way it’s on. Simple, light, and fault free.

As for fuel monitoring, an electronic probe/gauge system was installed.

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