Canopy Side Windows
From Bondline
Contents |
Canopy Side Windows on the 4 Place
Mechanical Difficulty: 
- 
Tip: Don't even THINK about doing this except in warm weather or unless you can move the canopy assembly to a heated room indoors. Its critical that the plexiglass temperature be at least a comfortable room temperature, and warm enough that you are sweating on it is even better.
Canopy Removal
The AA-5x canopy side windows slide in from the bottom, and that means that step one is to remove the canopy assembly from the plane. To do this remove the bottom row of screws on the canopy. There are 2 shims at the aft edge held on by the last 2 screws on each side, be sure to keep them for re-installation.
After all the bottom row of screws is out, the canopy can be lifted straight up and off of the plane. This ought to be done by at least 2 people, and 3 would offer an additional level of safety. With a helper on the opposite wing root, lift the canopy straight up, taking care not to scratch the quarter windows with the sharp corners at the aft edge of the canopy. Once the canopy is above the turtledeck height, carefully hand it over to one person on the wing root. The other person then gets off the wing and comes to the trailing edge of the wing so that the person holding the canopy can hand it down. The canopy should be placed upside down on a padded surface. A packing blanket or sleeping bag folded a few times is a good pad on the ground.
Taking the interior plastic trim out
The windows are clamped to the frame at the "bottom" by another row of screws that hold the bottom of the window frame in place. Remove the screws and the stiffener can be removed. The interior plastic is sandwiched between the stiffener and the outside canopy. The interior plastic can now be removed. There are screws and rivets along the front edge of the plastic under the canopy bow seal. Remove the seal. Its probably old and in need of replacement anyway. A stiff bladed putty knife can help shear the glue that holds the seal in place. Use 3M General Purpose Adhesive Cleaner to soften the glue and remove it from the bow. Under the glue the pull rivet heads and the screws can be found.
Remove the screws and carefully drill out the rivets. Best practice is to use a small punch to tap the rivet stem back out of the way and then drill the rivet using the mandrel hole as a pilot. Use a 1/8th inch drill bit to avoid drilling the holes over-size. You will notice that the rivet holes here are countersunk in the front. Avex 1604-0412 blind rivets fit the bill here nicely when you go to re-assemble. (You can order them from your favorite supply house, they cost about a nickel each. Buy a dozen so you have extra for the future)
There are a series of rivets along the aft bow of the canopy as well. Remove them the same way as those of the front bow. These rivets are Avex 1601-0410, and once again, they are inexpensive, so buy a dozen.
With all the rivets and screws at the 2 bows out of the way, remove the #4 screws that hold the cover on the canopy latch and the center panel of the headliner in place. Remove the #6 screws above each window and the interior trim should now be free to come out.
Removing each window
The windows slide in the tracks, hence the need for the plastic to be warm. With the curvature of the canopy, the window must bend to slide out or in.
There is not much spare room to maneuver the window in the tracks, so the best plan is to "walk" it out about 1" at a time, alternating front and back. This takes 2 people to hold the canopy frame and move the plexi. Grasp the window by putting a flat palm on the inside and outside and pulling one end of the window out of the track slightly. When it moves, no matter how small the movement, position your hands on the opposite end of the window and repeat the pulling until it moves again. Keep swapping ends and walking the window out of the frame. After a few inches it may be easier to pull on the exposed edge of the window along the "top" of the plexi. Once it is completely out, the canopy shell is going to be very wobbly. Be careful not to damage the aluminum shell while the windows are out.
Preparing the new window
Because of manufacturing tolerances, the bonded tracks can vary in distance apart, and its occasionally necessary to trim as much as 1/8" off one side of the window to let it fit the tracks. Measure carefully the length of the old windows and compare to the new ones. Sand or file the new one(s) if they are longer than the old ones.
Sand the edge of the new window completely smooth with sand paper in a succession of grits ending at no less than 400 grit. The goal is to remove the tool marks on the edge to leave a stress free surface. Be sure to wrap some sandpaper on a wood block and chamfer the sharp edges of the plexi with a small radius. Plexiglass expands and contracts much more than aluminum when subjected to "normal" temperatures on the ramp and in flight. This continual changing in size causes any discontinuity in the edge to become a stress concentration, and leads to small cracks and crazing in the corners, long before the window should need to be replaced. Examine the old windows on most light planes and you'll see those cracks forming in the corners. If you are using the Fletchair foam tape, it is best applied with some stretch to it, especially as you go around the corners of the plexiglas. This will make the tape "sit" down flat on the corners. This tape has a high "stickiness", and cannot be re-positioned, so apply it carefully.
Installing the new window
With the practice gained by walking the window(s) out of the tracks, you have learned the basic skill needed to re-install the windows. Lube each track and the felt or foam tape with a generous coating of clear silicone spray. Insert the window into the the track and line up both ends so that they start together. Now carefully walk the window into the tracks. The goal is NOT to wedge it tight on either end, but just take the movement that will easily happen, stop and swap ends to move the other end a little.
You can NOT force the plexi! Any suggestions of "putting a block of wood on the edge and hitting it" should be considered an admission that you didn't properly prepare the plexi, or that you are using the wrong technique. At the second Cody Convention in 2002, a group had been working to do a canopy window installation as a demonstration, and after much struggling by various persons that should have been able to install it, I was called upon to assist. After removing the jammed window from the frame and inspecting for damage to the foam tape, the plexi and the canopy shell, I re-lubed the window and the track and installed the window in a smooth easy motion alternately applying pressure at each end as I felt the resistance building and was later told that it took 41 seconds to install the window. I freely admit it usually takes 2-3 minutes to walk one into place, but I have NEVER found the need to resort to excessive pressure or hitting the plexi to drive it in.
