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Fuel Selector

Im looking to see if we could change out the fuel selector for a type of "pass through" fuel valve of sorts? The wobble pump doesn't work anymore as someone added a boost pump (primer pump) to the fire wall and disabled the wobble pump. Im wanting to remove the wobble pump all together and install some sort of mixing valve for all three tanks.. Not even sure if that's possible. Any advice would be great. TIA

Model: Bonanza 35
Aircraft Serial Number: D2523
Posted 3/26/2023 - 1 year ago
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I'm curious as to the 'primer pump' installation. I'm going with the rest of your post as being an otherwise unmodified B35 with an E-series engine. I know of no STCs that allow for disabling the wobble pump when installing a electric pump on these aircraft as described. In the annals of history of the old BDS (Beryl D'Shannon) STCs there was (at one time) the ability to change the fuel selector on the aircraft that had an IO engine installed per their STC; I did that modification once under the STC, and once as a field approval.

I would suggest reviewing the change made to disable the wobble pump and make sure it is an approved change; it would display on the STC, as well as the flight manual supplement that discusses the use of the electric primer pump.

To answer your question: If the installation is an auxiliary fuel pump, and not just a primer pump, you / your A&P can apply for a field approval to change the fuel selector to the later style, but will still need to return the fuel to only the left main unless your approval also gains the ability to return fuel to the right, but that would also come with additional plumbing changes. To get that, you will need a very good relationship with your FSDO.

As far as a mixing valve, if you are suggesting being able to draw from both mains at one time; I seriously doubt that can be approved.

My apologies for being Debbie Downer.

Mike
ABS Tech Advisor

Posted 3/26/2023 - 1 year ago
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Mike is not being negative, he is being realistic. Fuel system changes are “major alterations” and require either an STC or Field Approval. The stock BE35 fuel system is extremely well designed and reliable.

Posted 3/27/2023 - 1 year ago
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Fuel Selector