5.3.0 Door Latches

The first step is to clamp the door onto the worktable so that it doesn’t move around while working on it! You can see the factory markings (black Sharpie) which provides a guide for where the latch is to be installed as well as where the four latching rods go.

Fuselage - Door Handle Installation 1

Prepping the door for the installation of the door handle and latching mechanism.

Here’s a closeup showing the location and orientation of the latch plate. I’ve already pre-drilled a 3/4" hole, down to the outer skin, for the bearing carrier.

Fuselage - Door Handle Installation 2

The factory pre-marks the location for the mechanism.

The latch plate base needs to have three holes drilled for the rivets used to hold the bearing carrier and spring rod and pivot assembly. The factory does not provide a template for this, so I fired up my CAD program and made my own.

Fuselage - Door Handle Installation 3

Rivet location templates.

You can see the riveted spring rod and pivot assembly on the right side of the plate. The ends of the rivets actually had to be filed down a bit so that the rod and spring cleared them. The same holds true for the latch stop bracket in the middle of the plate. What you can’t see in this photo is the bearing carrier - it’s under the handle and latch crank assembly. My plan initially was to rivet that to the plate, but there wasn’t enough clearance for my rivet gun, so I ended up bolting the bearing carrier to the plate. That worked perfectly. In a way, that’s an improvement since now I can remove the bearing carrier if I ever need to replace it. The entire assembly is firmly attached to the door itself with structural epoxy and rivets. You can see two of the rivets next to the spring rod and pivot assembly - the other two are hidden under the latch crank.

Fuselage - Door Handle Installation 4

Inside door handle, now installed, in the "open" position.

Fuselage - Door Handle Installation 5

And here's the door handle in the "closed" position!

The rods and latch pins are now installed. The factory pre-drills locating holes for the latch pins which need to be enlarged for the latch pin tubes. The tubes are made out of steel and once fitted into position (making sure there is no binding of the latch pins) they also need to be ground down a bit to match the contour of the outside edge of the door frame. That was pretty easy to do with my belt sander. Once everything fits nicely, the tubes are installed with structural adhesive.

The rods and latch pins fit perfectly on one of the doors but were a bit off on the other door. I’m not sure why, but I had to fix that problem. The pin at the bottom in the photo below (closest to the handle) stuck out about a quarter inch too far when in the “open” position. After consultation with the factory, I was told to just grind down that pin to make it fit. Ok, so that’s what I did, going back to the old belt sander. I chucked the pin into my drill so that I could spin it while trying to remake the taper on the end. That worked just fine!

Fuselage - Door Handle Installation 6

Co-pilot side door showing the latching rods and pins in place.

The latch pins need to engage in the latch pin tubes that get installed along the door frame in the fuselage. The photo below shows one of those tubes. There are four per door. Aligning these tubes ended up being fairly simple. With the doors installed and closed, I “locked” the door so that the latch pins stuck out. I then installed the tubes in the pins to check for a nice, tight fit. I had to do a bit of grinding and some adjustments here and there on the fuselage as well as the tubes themselves to get the angle of the tube opening to match the fuselage. Once everything looked good, I used my hot glue gun to temporarily hold the tubes into place. I then was able to test the latching mechanism to make sure it all worked. Some tubes still needed adjusting and it was fairly easy to break them away from the glue. Once I was happy with the operation of all four pins, I used EZ-poxy with micro-balloons to permanently attach the tubes and to smooth out the transition between the tubes and fuselage for the 2 BID layup that goes over the tubes. You can see the final result for one of those tubes below. The rest look pretty much the same.

Fuselage - Door Latch Pins

Closeup view of a door latch pin inserted into one of the tubes mounted to the fuselage door frame.

Now that the latch pins and tubes are finished, it’s time to work on the door latch mechanism. The system is fairly simple, yet making sure it’s all aligned properly, especially for the pilot side door, is a bit tricky. More about that later. (The co-pilot door is indentical except for the door lock and the fact that it doesn’t have an external lever for releasing the latch.) The factory supplies that solid rectangular block of aluminum with an offset hole drilled through it for the locking mechanism. In my case, it wouldn’t slide over the latch pin rod, so I had to drill out that hole to be slightly larger. I placed the u-channel aluminum piece per the manual, then locked the rectangular block into place on the rod with a roll pin. Once everything is in place and aligned, the u-channel gets riveted and epoxied into place using structural epoxy. The photo below shows the end result.

Fuselage - Door Latch Mechanism

Four rods are used to latch the door in place. This simple mechanism activates those latch pins.

Here’s the completed locking mechanism. This is the pilot’s door so I also had to install the lock cylinder assembly. The lock is not yet installed here. I’ll put that in much later - don’t want to have to keep unlocking it to open the door! The pin that’s installed in the u-channel (pilot side) can be operated either from the inside or from the outside. What makes doing this on the pilot door a bit harder is that the locking mechanism needs to be built before the u-channel is epoxied into place because of the extra perpendicular pin that is welded to the main pin (you can’t see it in this photo). It’s impossible to install the pin into the u-channel with that other pin sticking out. 

Fuselage - Door Lock Cylinder Fitting

The lock itself is not yet installed, but the fitting for the cylinder is now epoxied into place.

The photo below shows the key lock in place for a test fitting. I did this before I permanently glued the the cylinder in place.

Fuselage - Door Locking Mechanism

Closeup view of the door locking mechanism including the key lock.

With all of this mechanical work completed, it’s now time to install the windows. That’s quite a process and, while you would think it would be easier than installing the other windows in the fuselage, it isn’t. Click here to head to Section 5.3.5!

ui© John Trautschold 2018