While working on the forward fuselage a while back, I gave some thought to how the SDS EFII fuel pumps will be installed in the tunnel. The fuel pumps will rest on a shelf that is attached using the same pull rivets that hold the floor panels and tunnel access panel doublers in place.
Rather than installing a shelf that extends fully along the bottom of the fuel pump mount, as some others have done, I decided to create two smaller shelves at each end of the pump mount. I started by cutting 4 pieces of 3/4"x3/4"x1/16" angle to a length that would span 3 rivets (with appropriate edge distances) along the floor panel rivet line in the tunnel sides.
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| Angle shelf supports cut to length and deburred |
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| After marking a line down each support 5/16" from the edge, I marked and drilled a #30 hole to use as the initial rivet hole |
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| Initial rivet holes drilled in all angle supports |
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| Angles were then clecoed in the appropriate locations in the tunnel ensuring that the shelves would support the entire length of the fuel pump mount, and remaining holes were match drilled into the angles from the tunnel side panels |
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| All holes to attach the angles to the tunnel drilled and deburred |
Next I took a piece of 1/16" aluminum that I will not be using and measured and cut two pieces that will span across each pair of angle supports
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| I cut the pump assembly supports from a piece of 1/16" sheet that is meant for a landing gear mount service bulletin. I do not need to perform that service, but this extra sheet will not go to waste. |
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| I cut the shelves to span the width of the tunnel and the length of the brackets at their planned install locations. This was done prior to installing the forward floor panels. However, once the floor panels were installed, the tunnel sides were pushed in a little which meant trimming about 1/16" off the side of each shelf. Above the shelf panels can be seen prior to trimming. |
I temporarily bolted the Andair fuel valve to its bracket, steel fuel fittings to the firewall, and attached fittings to the SDS fuel pump assembly. I then located the correct Aircraft Specialty fuel hoses (H6 and H9) that connect the fuel valve to pump assembly, and the pump assembly to firewall and temporarily attached those in place just tightening each nut until it was snug.
The hoses help set the location of the fuel pump assembly on the shelf, and with everything snug I was able to confirm that
- the shelf supports were at the correct rivet locations in the tunnel
- the pump assembly was roughly centered on each shelf
The valve to pump hose being the shorter of the two has more influence over the pump assembly positioning, but it was good to verify both hose lengths worked well.
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| Fuel valve to pump hose (H6) |
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| Fuel pump to firewall hose (H9) |
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| Overview of pump assembly positioning |
With the pump shelf bracket positions verified, I was able to complete riveting of the forward floor panel to tunnel flanges in all locations except where the pump shelf brackets will reside.
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| Pump shelf bracket rivet holes left open so that parts can be removed for further fabrication |
In order to match drill the fuel pump assembly attachment holes to the shelving in the tunnel, I decided to permanently attach the tapered AN fittings at each end of the pump assembly. After spreading Loctite 567 around the middle few threads of the AN fittings, I screwed them in until they were finger tight and then used a wrench to add an additional ~1.5 turns being careful to ensure that the clocking on the aft fitting was correct.
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| Loctite 567 applied to the aft AN fitting |
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| Aft AN fitting after being fully tightened and clocked in the right direction. The Loctite 567 creates a nice even seal around the threads as it is squeezed out while tightening |
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| Loctite 567 sealant applied to the forward fuel pump AN fitting |
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| After tightening both AN fittings, I temporarily reattached both fuel lines to the fuel pump assembly (finger tight), and let the fuel pump assembly sit on the shelves without any force on the fuel lines |
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| Using a #19 right angle drill, I then match drilled the fuel pump assembly attachment holes into the shelving |
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| Four fuel pump assembly attachment holes match drilled into shelves, and shelves removed from tunnel |
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| Using a nutplate to match drill nutplate attachment holes into the shelves, making sure that the rivets would not interfere with the shelf attachment brackets. The nutplate attachment holes were countersunk to have the rivets flush on the top side |
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| I also lightened the shelves a little by cutting away portions that were not needed to support the fuel pump assembly load |
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| All fuel pump shelving parts ready for priming |
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| After priming, the fuel pump assembly and shelving were once again test fitted in the tunnel to ensure the bolt holes aligned |
The shelves and brackets were then riveted together along with the nutplates to hold the fuel pump aasembly, and these were then riveted into the tunnel (after running brake line hoses that pass under the shelves)
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| Forward and aft shelves ready for riveting in the tunnel |
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| Nutplates clear the attachment brackets nicely |
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| Shelves riveted into tunnel. This completes all rivets in the forward cabin floor flanges |
Dates: June 1 2025, December 15 2025, June 12 - June 22 2026, September 1 2026
