Sump Tank Inner Flange

An inner flange to assist with joining the two halves of the sump tank was constructed by  making a plywood sheet with a cutout slightly smaller than the opening in the tank.  The inner surface of the plywood was covered with duct tape for release. Working inside the lip of the plywood, 2x BID was laid up inside the tank edge and onto the plywood.

I let this cure a couple of days before trying to remove the plywood sheet.

Nose Landing Gear Guides

Guides were constructed to keep the nose wheel straight as it retracts through the nose gear doors.  This is to ensure that the nose wheel does not catch and hang on the doors or the edges of the nose gear door opening during extension.  That would result in a “bad day” and substantial repairs.  Plans call for making the guides out of a few layers of BID, but I chose instead to make them a little bit beefier, making a composite sandwich with some 3/8″ divinylcell foam.

A big sheet of sandwich was made, then the nose gear guides and supports were cut out with a jigsaw.  Foam was removed from the edges in preparation for some micro.

Sump Tank Construction

The factory supplies the two halves of the sump tank.  Mine had harping pre-installed for the two fuel inlets and the fuel outlet to the engine.  I had to install the hard points for the vent, the sump drain, and the float switch.

The entire inside of the tank was sanded to prepare for sealing and also for the hard points, which were glued in with cabo paste, filleted, and the covered with 2x BID.

Repaired Nose Gear Hydraulic Actuator

After repairing the seals, glands, and O-rings in the nose gear hydraulic actuator, I hooked it up to the nitrogen bottle and tested for leaks in both travel directions.  All secure!  The actuator was installed into the airplane and the nose gear retraction test and dump valve worked flawlessly, holding in the gear-up position for several hours with no noticeable loss of pressure.

Nose Landing Gear Retraction Test- Not

I wanted to test the nose gear retraction system and get the actuator limits set correctly prior to moving on to other things. Instead of hooking up the hydraulic pump and having to potentially chase hydraulic fluid leaks, I decided to use gas.  Yes, there is a stored energy concern compared to using hydraulic fluid, but its still a good first test if I am careful.  I got a nitrogen cylinder and a regulator and hooked it up to retract the nose gear.  The actuator brought the mechanism out of over-center at about 200 psi, and at about 300 psi, the gear quickly sprung all the way up. After closing the nitrogen cylinder valve, the pressure quickly decreased and the gear fell back into the extended position – clearly a leak somewhere.  I got some snoop (soapy water) and started checking fittings but it became pretty clear that the external fittings were not leaking but the actuator cylinder was leaking internally.  This discovery made the test worthwhile.

I removed the nose gear actuator cylinder (PITA) from the keel, disassembled it, and found that the actuator piston o-ring and backer ring were deformed, “rolled”, and torn.  Although the actuator had oil in it, and moved easily, it looked like the piston had been inserted dry during initial assembly.  The end piece o-rings and backers were in good shape, but I will replace them anyway during rebuild.