Quarter Windows
From Bondline
Contents |
Introduction
Maintenance Difficulty:
The quarter windows are very similar on the AA-1x and the AA-5x series. The AA-1x windows and the AA-5 windows before the '74 model year (those without a baggage door) are cut from flat acrylic sheet. AA-5 and AA-5x from '74 year model through the current production AG-5B Tigers have windows that have been heat formed to a compound curve.
To remove the quarter windows
Remove the interior trim surrounding the window. There are a series of very small sheet metal screws (#4) that hold the plastic trim on. There are a few more screws at the forward edge of the turtle deck that clamp the forward edge of the plastic trim, these must be removed, too. An offset rachet screwdriver with a #1 phillips bit will prove useful in the removal of all of the trim screws.
With the plastic trim off, now would be a good time to inspect it for cracks and chips, and perhaps repair it using the methods in the maintenance manual. More info on interior plastic repairs is available on Bondline.
Under the plastic trim are several small formed aluminum brackets that clamp the window in place. Remove the screws that hold the clamps in place and pop them loose from the plexiglass with a putty knife if needed. Sometimes the sealant that the window is bedded in can cause the clamp strips to adhere.
Remove the window
Probably some prying with a thin bladed putty knife will be needed to free it from the fuselage. After the window is out remove all traces of the sealant putty on the fuselage window frame. This will likely be quite hard from age, and require some careful work to break it free. Some will come off in strips or chunks and other sections will have to be scraped off. Use care not to score the aluminum structure and sand the inside lip smooth after all putty is removed. A coat of a quality brand of rattle can red oxide primer will restore the look and some of the corrosion protection of the OEM primer used on the planes from mid 76 on.
Prepare the new window
While the primer is drying sand the edge of the new window completely smooth with sandpaper in a succession of grits ending at no less than 400 grit. This can also be done with automotive finish wet-and-dry paper, use plenty of water to remove the sanding residue as you are working. 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.
Even factory installed windows were not always the correct size for the mounting area. This picture shows the result of a too tight fit. Make sure there is enough clearance around the plexiglas to allow for expansion and contraction. This crack started at the spot were the plexiglas is touching the metal frame.
Clean the window and frame
Once the edge of the window has an even "fogged" look to it with no scratches or tool marks left, clean away all the sanding dust (a vacuum is helpful) and avoid any rubbing motion that will scratch the window with the dust and abrasive particles. Apply the self-adhesive felt or the foam tape to the edge. A 1" wide piece applied exactly on the center of the edge will fold over about 7/16" on both sides and can be rubbed to a smooth wrinkle free surface.
Install the new window
Place the window up into the frame by inserting the TOP edge in first and then lifting the bottom edge up and sliding it into position. The window must bend to match the curve of the fuselage. The AA-1x and early AA-5 windows will tend to spring back flat and be harder to position than the later AA-5x windows that were formed to a curvature. They will require some bending to install, also, but will not tend to spring back flat because they are already close to the correct contour.
Replace the clamp strips, and install all the screws loosely before tightening any of them. Evenly tighten the screws in a couple of steps, so as to apply even pressure to the entire window. Reinstall the plastic trim. You might want to replace the old trim screws, which are probably looking rough, with some brand new #4 stainless screws. A bag of 3/8" and a bag of 1/2" long screws will replace the 2 lengths commonly used on the interior, and give you some spares for other locations in the cockpit.
To help restore the wind and water tight seal around the outside of the window, work some 3M Strip Caulk into the small gap between the plexi and the fuselage opening. I have had good results with a popsicle stick or tongue depressor as a tool to press the sealant into the gap, and to work as a smoothing tool to put a nice radiused fillet on the window to fuselage joint. The strip caulk wipes off the paint and plexi with a clean cloth after the gap is filled. Some installers prefer to mask the window and the paint with some low adhesion tape to speed the clean up. I have tried it both ways and think that it takes about as long to mask and remove as it does to clean up without the tape.
