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After I installed an electrical system in my Pitts last year I had on the list to replace the United Aircraft Products D2 wobble pump. I've have had to rebuild the wobble pump several times over the years mosly to reseal the shaft packing. The tell-tell there is the fuel pressure will start to jump quite dramatically and occasionally and you will get a very small nearly negligible leak at the shaft. The fuel pressure drops are because of small amount of air is passing by the shaft. It will also mess up the fuel flow indication or make it a bit more erratic. Its easy to rebuild but the thought of wobble pumping my way to a landing seems crazy now that I have an electrical system, so, no excuses. I know there are several 27-30 psi pumps out there and I considered many if not all of them, but I really like the size and weight of the Andair PX375-TC pump. It is however very expensive, but I take the approach,"The cost is long forgotten but the quality remains". It however was never in stock anywhere for over 6 months, I even emailed Andair directly. It finally came into stock at Aircraft Spruce so I jumped on ordering one.
I removed and weighed the wobble pump to find that its 3.375 lb. The Andair pump is 1.01 lb. I needed a way to adapt the wobble pump bracket to fit the pump as I wanted to the least amount of fuel line changes as possible. Turns out all I had to do is introduce a 45 bend out of the exit of the wobble pump line and shorten the input by about 1/2" and re-flair it. I had some left over carbon 7ply flat stock from my instrument panel built and made a quick bracket to adapt to the wobble pump bracket and mounted it and the pump to the plane.
I installed a switch in to my instrument panel and labeled it. I ran the power wires and installed a new 7.5A circuit breaker into my electrical bus.
Ops checked good and was leak free. Quick and easy 2.2 lb reduction.
I removed and weighed the wobble pump to find that its 3.375 lb. The Andair pump is 1.01 lb. I needed a way to adapt the wobble pump bracket to fit the pump as I wanted to the least amount of fuel line changes as possible. Turns out all I had to do is introduce a 45 bend out of the exit of the wobble pump line and shorten the input by about 1/2" and re-flair it. I had some left over carbon 7ply flat stock from my instrument panel built and made a quick bracket to adapt to the wobble pump bracket and mounted it and the pump to the plane.
I installed a switch in to my instrument panel and labeled it. I ran the power wires and installed a new 7.5A circuit breaker into my electrical bus.
Ops checked good and was leak free. Quick and easy 2.2 lb reduction.
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