Archive for March, 2023

Pressure sensors replaced

Monday, March 6th, 2023

A service bulletin on Kavlico fuel and oil pressure sensors was published a couple years back, advising of a potential for them to leak. I decided to replace them both just to be safe. I was able to remove them both while leaving the transducer manifold in place, although it was a tight fit due to how crowded this area is:

I replaced the oil pressure sensor with another Kavlico sensor – the gold thing at the top – this time the supposedly non-leaking kind. I found that the correct Kavlico fuel pressure sensors were difficult to come by, so I was forced to buy one of Garmin's new private-label sensors – it's the silver cylinder at the bottom of the manifold. The manifold pressure sensor I left alone, since it wasn't subject to the same service bulletin.

At least the wiring connections are the same as the old sensors, so not a bad job overall.

Posted in Electrical/Panel, Firewall Forward |

Manifold pressure hose upgrade

Monday, March 6th, 2023

I didn't like the ugly way I'd previously hooked up the manifold pressure plumbing, so I had TS Flightlines make me a braided Teflon hose to use instead. No more plastic tubing under the cowling:

The hose goes around behind the engine mount and across the firewall, supported by adel clamps:

It's adel clamp city to get the hose where it needs to go without rubbing on the engine mount or chafing through any wires. You can also just barely see where I used a bolt and a couple washers to plug the hole in the firewall where I'd previously had a bulkhead fitting installed:

The single bolt and pair of adel clamps that hold the hoses here took me an hour to install, due to the lack of access:

If I had it to do over again, I'd either mount the manifold pressure sensor closer to the #3 cylinder, or else pick up the manifold pressure reading from the #4 cylinder on the other side of the engine using a much shorter hose. But this is good enough.

Posted in Firewall Forward |

Fuel system plumbing

Monday, March 6th, 2023

Having finished all the electrical tasks in the lower-forward fuselage that I can conceive of, I should hopefully not have too much more crawling under the panel in my future, so there's no reason not to install the fuel plumbing for good. I retrieved the fuel pump/filter unit from storage, touched up the paint on the selector valve plate, and installed the whole assembly in the fuselage with screws:

Next I fabricated the remaining fuel lines that go between the wing tanks and the selector valve. I'm really glad I decided to make these in two pieces, with a bulkhead fitting in each F-783B cover support rib, because it would have been a nearly impossible task to fabricate these lines as a single piece. As it was it was still difficult – even though it's a pretty simple component, the lack of access and the fact that you have to bend and flare it in situ results in a fairly challenging job.

At each outboard side I used zip ties and a piece of rubber fuel hose to prevent the wiring bundle from chafing on the fuel line:

The plans call for a block of styrofoam to support the line that runs forward from the fuel pump to the firewall. I started with some craft foam and a hot-wire cutter:

I split the foam in half and cut out a groove for the fuel line. I like cutting foam with this tool, much less mess than traditional cutting tools – just try not to breathe the fumes.

Fuel line and foam support installed between pump and firewall – the foam block is held together with a strip of clear packing tape:

Out in the wing roots, I fabricated and installed the 1/4" vent lines that run from the tank to the fuselage, snaking around the tank attach bracket in the process. In the background you can see the 3/8" line that goes from the tank outlet into the fuselage:

As a final step in finishing the fuel system, I removed the plastic plugs from the bottom of tanks and installed the fuel quick drain valves:

It's kind of wild to think that, in theory, I could probably fill the tanks and start the engine almost any time I want. Well, a set of working brakes would probably be good first. Still, feels like progress.

Posted in Fuel Tanks, Fuselage, Wings |