Fuel System

Diagram of the fuel system layout (provided by Tony Jurcan)

This page consists of a description of the fuel system installed in the most recent Seawinds to come out of Bowes Aviation.

A review of the ISPA incident log, just as a review of most aircraft incident logs, shows that a high percentage of aviation incidents stem from fuel system problems and anomalies. For this reason, SNA (the manufacturer of the Seawind and Seawind kits) has understandably been outspoken about builders making any changes to the factory designed Seawind fuel system. Please, any modification to the fuel system must be done with a thorough review by the experts. Installation of the system shown here must be done with close coordination and review by Bowes aviation.

Bowes Aviation and the ISPA are providing this page not as a recommendation, but for information only, and are not liable for it's use.

The ISPA thanks Mike Bowes for the text on this page, and Tony Jurcan for the sketch.

Dual header tanks shown above next to the MLG retract arms for size comparison.

As many of you now know, N369JB has a dual header tank fuel system that feeds into an Andair Left, Both, Right, Off fuel selector valve. Fuel then passes through a stainless mesh fuel filter and then through an electric boost pump on its way to the engine's mechanical pump.

In the beginning, I really didn't want to talk about my set-up or advertise it in any way because it was unproven. Also, I had done the unspeakable. I had MESSED WITH THE FUEL SYSTEM!

It's a different story now, though. The aircraft has been flying for a year and a half and now has 178 hours on it. The system performs exactly as I had envisioned it would, and gives the pilot total control over the fuel in the two [main] tanks. Most Seawinds I have flown exhibit a tendency for one tank to feed a little faster than the other. The reason this happens has been discussed at length elsewhere and the subject can be debated all day long. It is not my purpose to go into the reasons here and now. Simply accept that this is a fact of life that shows up on longer flights and the standard "Both on" or "Both off" system gives you no opportunity to balance fuel by controlling which tank you're burning, as in most other aircraft.

My system remedies this perennial problem without forcing the pilot to resort to the use of electric crossover fuel pumps. N369JB has the crossover system installed, but I never need to use it. Simple is beautiful. Because the Andair valve does not permit cross feeding from a high tank to a low tank, EVEN WHEN SELECTED TO BOTH, my system requires no check valves. Check valves slightly impede the gravity feed of fuel coming out of the tanks.

Those who attended the 2003 Fly-In were seemingly eager to learn all about the system on N369JB which is being duplicated in the shop right now on the Richard Wolf Seawind. For the first time, I was willing to talk about it and explain the Bowes system features in detail. I would suggest this is not something you can retrofit. Fuel lines must be installed prior to bonding down the floors.

[The following provides] specific model numbers for the valve and the dual fuel pump setup, company names, and phone numbers. I have gone back into previous month's invoices to research this stuff and save all of you time and possible aggravation. Enjoy and happy building.

Andair Ltd. Unit 15 The Tanneries, Havant, Hants PO9 1JB England

Phone: 011 023 9247 3945, 5 hours time difference, so call early in the morning and you'll catch them before they leave work.

Valve model number FS25B4-B Fuel selector with 3 banjo fittings. Total cost including shipping was 239 Pounds Sterling which converts to about $405.00 US, and worth every penny.

Airflow Performance Inc. 111 Airflow Drive, Spartanburg, SC 29306

Phone: 864-576-4512

#8 Dual Fuel Pump Package part number 3090080 #8 Maintainable Fuel Filter part number 1090161 Don Rivera will include all cushion clamps you need to mount this stuff. Total bill including shipping and insurance to Florida was $713.00.

Mike and the mechanics, N369JB

Dual header tanks are constructed from 3" by 3" square aluminum tube and capped with 1" by 3" aluminum angle. All material thickness is 1/8". The tanks incorporate only 4 fittings each. Aluminum welding bosses are available from Spruce and Wicks. You will need a pair of 1/8" NPT and a pair of 3/8" NPT fittings. The small ones are centered in top and bottom of tank for static vent and sediment drain, respectively. The pair of bigger ones create an "Inflow" port and an "Outflow" port. That is, in from the wing tank, and out to the Andair selector valve. Both of these bosses should be welded onto the forward facing side of the tank, more or less side by side, as space permits. On N369JB, the inflow occurs about 4" up from the bottom of the tank. And here's the most important point. Picture this. The outflow occurs about 5 inches up from the bottom of the tank. Very important!Compare this to your "stock" SNA tank where the outflow is right at the bottom. There really is no sump to trap condensation and sediment matter and contain it in the tank. My design assures a 4" to 5" deep sump to trap these nasties and give you an opportunity to "sample them out" onto the ground, during preflight. This system also eliminates the large red check valves. These are no longer necessary, as the clever design of the Andair valve does not allow for main tank cross-feeding [when selected to "Off." It will however allow cross-over between the tanks when in the "Both" position.] (See clarification below.)

Low points are bottoms of each header tank, which each have their own quick drain in the main gear pockets on both left and right. I sump these drains before and after each flight.

If desired, you could also "T" and create a sump drain in the main line after the selector valve, headed up to the engine. Locate the quick drain in a "pocket" facing aft, on the vertical part of the hull step, for example. I opted not to do this, reasoning that high velocity fuel through this tubing during operation periods of the electric boost pump (during engine start, for takeoff and for landing) would eject moisture from this area, anyway.

We should note that fuel tank venting is done exactly as the SNA manual shows you. Header tank venting is also as per manual instructions. The header vents simply come together at a "T" and run on up to the SIDE of the tail. Sediment drains, also, are by the book. Only difference is you have a drain in both wheel pockets instead of just the left one. Mike, chief sediment sampler, N369JB


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The following update was added by Mike Bowes in post #917 on October 20, 2003:

Boy is my face red! I mean crimson. The ranting and raving I've been doing about how this valve will not pass fuel from one side to the other when selected to "BOTH". Not correct, sorry to say.

Guys, I am so sorry, this was the impression I had formed from observing my own airplane over the past 18 months. I guess Seawind N369JB has been parked consistently on flatter ground than I realized.

We had a lively debate in the shop today, concerning what built-in design features the valve must incorporate so as not to allow transfer of avgas from a high tank over to the low tank when selected to "BOTH". The final consensus was there must be built-in check valves...it was the only thing we could imagine that could produce this effect. Wrong!

I called merry old England and talked to Andy Phillips, at Andair, directly, late in his day over there. After explaining the nature of our debate, he laughed and, like a true diplomat, said we could all be right. The valve will not pass fuel from one side to the other only if it is selected to any other position but "BOTH". Unfortunately, he explained, it will in fact pass fuel from high to low if left in the "BOTH" position and parked on uneven ground, or when left sitting in the water with one wing low.

Therefore, I very much stand corrected and you just may want to install those big red check valves after all. Especially if you know you can't remember to move the valve position out of "BOTH" as you exit the airplane at the end of the day.

Myself, I will not install them at this point. I have found the system entirely adequate and much to my liking over the past 180 hours. Mike, humble pie eater, N369JB

The following photo and text was added April 24, 2004: Mike Bowes has sent us the photo at the lower right showing ISPA member Dick Wolf's dual fuel pump installation. One of Mike's dual header tanks can be seen along the left side of the photo.

Mike also provides the following text: "As always, a picture is worth a few hundred words, and this view of the Airflow Performance dual fuel pump and filter installation in a seawind is pretty much self-explanatory. The location is right side of the tail-cone with the right side of the photo being direction aft.

The incoming fuel line (coming from the Andair selector valve) rises up from under floor in lower left of photo. The outgoing, 25 psi line (going to the engine) is in the upper right corner. Incoming fuel hits the cleanable filter first, a good thing, and then on to the pumps. Fuel regulator bypass pressure is routed back to the incoming line ahead of the filter by means of a "T" fitting inserted in the vertical incoming line. Note there is a reducer bushing that changes the 3/8" pressure bypass line to 1/2" tubing immediately before the "T".

This is an example of one man's solution to the installation challenge. By all means, if you can improve on this, do so. It's a neat, compact, installation using sweeping curves of tubing and thereby eliminating a great number of additional fittings which might otherwise have been used. All components are easily visible and accessible for leak-checking and service, from time to time. Right site, left side of tail-cone doesn't really matter. You choose where you want to put it.

Hope this helps those of you who have decided to build in this equipment."

Mike, chief fuel plumbing guy, N369JB