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Osborne tip tank gremlins

We have three issues with our Osborne tip tanks, Kit No. 35668-1, installed many years ago, and (seemingly) working fine until after the right tip was repaired following damage from a taxiway accident. Mostly, but not always, fuel doesn't flow from the repaired right tip. (2) A tank switch diagram prepared by the A&P who did the recent annual doesn't match the post-initial installation placarding. (3) It's not clear to which tank excess fuel is being returned, depending on which tank(s) are being selected.
We desperately in need of being connected to someone/some shop with enough experience with this installation to help sort out what's going on.
I'm going to attach more extensive information to 'replies' to this posting, as previous attempts to post haven't worked.
Thanks,
Lee Harris, ABS #51432

Model: Bonanza K35
Aircraft Serial Number: D5847
Posted 8/8/2023 - 6 months ago
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Attached herewith a fuller description of what's been happening with the tip tank system.

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Fuel system history.pdf - 32.3 KB

Posted 8/8/2023 - 6 months ago
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This attachment describes behavior during the most recent flight.

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2023_07_31 Fuel Summary.pdf - 1.8 MB

Posted 8/8/2023 - 6 months ago
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Here's a diagram based on the work of the A&P we asked to check out the system at the recent annual.

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Fuel System.pdf - 29.1 KB

Posted 8/8/2023 - 6 months ago
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You indicated an odd sequence of how you expect to use fuel. The basic fuel system feeds as follows.
Standard system:
** Select left main, fuel is consumed from left main and return is to left main
** Select right main, fuel is consumed from right main and return is to right main
** Select aux, and fuel is consumed out of the aux tanks (theoretically, simultaneously), and return to left main
(The aux tanks feed to a cross by the fuel selector; left and right to the sides, top to fuel selector, and bottom to a drain down by the belly drain behind the door.)

Every F thru M 35 I have worked on that has the JLO / Brittan direct feed tips work the way I am about to describe (with exception to fuel return on the F thru H all returning to left main only).
** left main and right main as described above
(Two small fuel valves are installed, one is on-off for left tip only, other has positions for right tip, both wing aux (factory 10 gal ea.), and off)
** wing aux (2 X 10-gal each factory) main selector to aux, left small selector to off, right small selector to wing aux, return to left main. (Wing aux is not individually selectable)
** Right tip: Select main selector to aux, left small selector to off, right small selector to right tip, return to left main.
** Left tip: Select main selector to aux, left small selector to left tip, right small selector to off, return to left main.
** Both tips: Select main selector to aux, left small selector to left tp, right small selector to right tip, return to left main.

Factory wing aux fuel is only available through the right tip selector when in aux position, tip fuel is only available with small selector(s) set to tip(s), and in either condition the main selector needs to be at 'AUX' and all return fuel is to left main. You cannot draw fuel from more than one main tank at a time, nor add in wing aux or tip fuel at the same time.

The drawings your AP made up in your third attachment do not represent how it should be, but may represent how it is actually plumbed. If it is plumbed that way, you should have a flight manual supplement so indicating, as well as some form of paperwork approval (STC, Field approval, etc.) for changing the fuel system.

Posted 8/8/2023 - 6 months ago
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We flew yesterday to definitively determine the erroneous behavior of the tip tank system.

With the right, aft switch set to EITHER the 6:00 position ("aux only") OR 3:00 ("right tip"), fuel is ALWAYS pulled from the left tip until it's empty, regardless of the position of the aft, left switch. When the left tip goes empty, fuel continues to be pulled from the aux tanks, as expected.

If you switch to the right tip and the left tip is empty, the engine will stop, even if there's fuel in the right tip.

We don't believe there are any valves, etc. at the tip tanks themselves, and that something's not working properly in the fuselage mounted switching mechanism. If we could get a reference to someone who understands the workings of that switch so we can get this sorted out, we'd be most grateful."

Posted 8/18/2023 - 6 months ago
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Osborne tip tank gremlins