CABIN 1. GENERAL The aft passenger windows are manufactured of acrylic and adhesive bonded to the fuselage. Replacement is accomplished by removing the interior trim around the window, removing the sealant around the window, and then removing the window from the fuselage. In general, the reverse process is used to install a replacement window. This method is literally seamless, and the fuselage will show no marks or evidence of maintenance. Page 1
2. MAINTENANCE PRACTICES A. Aft Passenger Window (1) Removal - Aft Passenger Window (See Figure 1) (a) Acquire necessary tools, equipment, and supplies. Description P/N or Spec. Supplier Purpose Die Grinder (1-Inch Cut-Off Disk) - Any Source Cut window. Masking Tape 2-inch Any Source Prevent damage to the window. Drop Cloth - Any Source Prevent contamination. Isopropyl Alcohol 99% or higher purity Any Source General cleaning. Aluminum Oxide Sandpaper Phenolic or Hardwood Utility Knife 80-grit Any Source Sealant removal. 1-inch Any Source Sealant removal. (b) Remove the interior trim panels from around the window. (Refer to 25-10) (c) Cover the interior and instrument panel with a drop cloth to prevent foreign material from contaminating the interior and instruments. (d) Using several pieces of duct tape, make handles on the exterior of the window. Exercise care to prevent the removal of laminate from the fuselage when cutting and removing the sealant from between the fuselage and window. If laminate is damaged, it must be repaired prior to installing the window. If window is being replaced, it will be easier to use a die grinder and a cutoff disk to cut out the inner portion of the window to gain access to the bonding flange. The window should be cut as close as possible to the fuselage. (e) (f) Cut sealant loose from between fuselage and window using a small pocket knife. While pushing in on the window, follow the edge of the fuselage with the tip of the blade, then back cut in towards the fuselage to clean out the sealant. (See Figure 1) Using a phenolic or hardwood utility knife, isopropyl alcohol and aluminum oxide sandpaper (80-grit), remove all remaining sealant from the fuselage bonding flange. Page 2
BONDING FLANGE Cut window out next to bonding flange, do not damage laminate. Any laminate which becomes damaged must be repaired prior to inatalling the new window. WINDOW BONDING FLANGE SEALANT Push window inward while cutting sealant between bonding flanges. FUSELAGE BONDING FLANGE FUSELAGE (REF) SECTION SR20_MM56_4350 Figure 1 Window Removal Page 3
(2) Installation - Aft Passenger Window (See Figure 2) (See Figure 3) Window sealant is intended to provide an acceptable seal between the window and fuselage and to prevent the leakage of air through the airframe structure. Window sealant is used in the installation of all windows in the aircraft. Isopropyl alcohol, kerosene, white alptha naptha, mineral spirits, and cotton are acceptable for cleaning acrylic windows. Residue left behind by the Spraylat protective coating may be removed by soaking the area with isopropyl alcohol and rubbing with an alcohol soaked soft flannel cloth. Residue left behind by the adhesive backed paper covering can also be removed by the above method. If, however, the paper covering has been stored on the window for an extended period of time, soak paper with kerosene and keep it wet for several hours. Remove any remaining adhesive by using a mixture of equal parts of kerosene and isopropyl alcohol. Soak a soft flannel cloth with this mixture and rub the window with the cloth. The window should be cleaned after this procedure with a dish washing liquid and plenty of water. WARNING: Never use organic solvents such as Methyl Ethylketone (MEK), acetone, or lacquer thinner. Do not use jewelry cleaner or paper towels to remove any contaminates. Never use ice scrapers on acrylic windows. Do not store any window outdoors while the protective covering is still on the window. The covering will become very difficult, if not impossible, to remove without damaging the window. It is very important to keep the window well supported at all times. Warm temperatures are not required during these operations; however, acrylic will take much more abuse at 80 degrees than at 30 degrees. Always inspect the window before final installation. Use care to prevent staining or scratching the window. (a) Acquire necessary tools, equipment, and supplies. Description P/N or Spec. Supplier Purpose Padded Cargo Rods - Any Source Temporarily secure window. Masking Tape 2-inch Any Source Prevent damage to the window. Temperature-Resistant Sealing Compound MIL-S-8802 Type II, Class B (Refer to 20-10) Seal windows. Isopropyl Alcohol 99% or higher purity Any Source General cleaning. Cotton Gloves (clean, lint free) Cotton Cloth (clean, lint free) Application Spatula (nonnylon) - Any Source Protect hands. - Any Source Clean sealing surface. 1-inch Any Source Smooth adhesive. Page 4 Primer MC-145 LP Aero Plastics Aid in adhesion.
Description P/N or Spec. Supplier Purpose Protective Coating AC-940 Blue AC Products, Inc. Prevent damage to the window. Fine Line Tape (pin stripping) Sandpaper, Aluminum Oxide 1/4-inch 3M Company ow smooth transition between fuselage and window. 80-grit or finer Any Source Abrade acrylic surface prior to adhesion. Exercise care to protect the inner and outer window surfaces from damage during the installation process. The stepped area on the edge of the window (which is bonded to the fuselage) is called the bonding flange. (b) (c) (d) (e) Verify that sealant is within storage-life requirements. Inspect fuselage bonding flange for any remaining sealant or contaminates, remove and clean as necessary. Remove the protective covering from the window and inspect the window for damage or defects, never install a defective window. Install a continuous piece of fine line tape on the edge of the fuselage window opening (next to the bonding flange). (See Figure 2) The masking tape will provide a smooth and continuous parting line at the bonding flange. (f) (g) Working in one direction on the fuselage window opening, place 2-inch masking tape on top of the outer edge (the edge furthest away from the bonding flange) of the fine line tape. Make a directional mark on the masking tape to indicate the proper direction for removal. (See Figure 3) Do not apply protective coating on the window bonding flange. (h) (i) Apply three coats (in opposing directions) of protective coating (AC-940 Blue) on the outer window surface. Using several pieces of duct tape, make handles on the exterior of the window after the protective coating has fully cured. Five or more padded cargo rods may be necessary to hold the window into the proper position. Padded cargo rods may be placed on each corner of the window and in the center of the window. Additional padded cargo rods may be required to prevent the window from sliding down. (j) (k) Place window into position and secure the window into the fuselage using padded cargo rods. (See Figure 3) Inspect the window for proper fit. The window must have equal amounts of space around the perimeter of the window. The exterior surface of the window should be flush with exterior surface of fuselage. Page 5
The window bonding flange must never be trimmed to a thickness less than 0.080 of an inch. The window bonding flange must never be less than ½- inch wide. The window bonding flange should have equal amounts of space around it. If the window doesn t fit into the fuselage with equal amounts of space around it, the window and/or bonding flange will need to be trimmed accordingly. The window should be flush with the exterior surface of the fuselage. If the window cannot be made flush by adding moderate pressure on the cargo rods, the thickness of the window bonding flange must be trimmed accordingly. Aluminum oxide sandpaper (80-grit) on a sanding board may be used to trim the window. (l) Mark and trim the window as required to ensure a perfect fit. Five or more padded cargo rods may be necessary to hold the window into the proper position. Padded cargo rods may be placed on each corner of the window and in the center of the window. Additional padded cargo rods may be required to prevent the window from sliding down. (m) Place the prefit window into position and clamp the window into position using padded cargo rods. Page 6
BONDING FLANGE HANDLE Trim window as required to ensure equal spacing on all sides NOTE Placement of padded cargo rods. Trim window thickness as required to obtain a flush fit to fuselage. Trim window bonding flange as required to obtain a 0.5 inch flange. Apply protective coating on window to prevent damaging window during the installation process. 0.080" MINIMUM WINDOW BONDING FLANGE 0.5" MINIMUM FUSELAGE (REF) SECTION Figure 2 Window Alignment SR20_MM56_4351 Page 7
(n) (o) (p) Remove a small amount (approximately 2-inches wide) of protective coating from around edge of window. Install a continuous piece of fine line tape (pinstripe tape) around the edge of the window (next to the bonding flange). The fine line tape should be adhered to the window with equal amounts of space between the fine line tape on the fuselage and the fine line tape on the window. Working in one direction on the window, place 2-inch masking tape on top of the inner edge (the edge furthest away from the bonding flange) of the fine line tape. The alignment marks will be used to ensure that the window will be installed into the exact location in which it was during prefit. (q) (r) (s) Using a straight edge, make several alignment marks around the edges of the masking tape on the fuselage to the masking tape on the window. Carefully remove window from fuselage. Using aluminum oxide 80-grit paper, abrade the bonding flange of the window in a random pattern. Remove all surface gloss. Wax or grease pencil markings on any part are not allowed. Any such markings inadvertently occurring must be removed prior to application of primer. surfaces shall be thoroughly cleaned and dried before application of primer. Immediately prior to applying any primer on the window bonding flange, solvent clean the flange with isopropyl alcohol. When handling cleaned surfaces, wear clean cotton gloves to prevent surface contamination. Surfaces must be re-cleaned in the event of contamination. Fold cloth in such a manner to eliminate raw edges to reduce the possibility of lint. Always clean an area larger than the application area. (t) Remove contaminates from the window bonding flange and the immediate work area using a vacuum and a clean brush attachment. Do not apply primer to the composite bonding surface. (u) Ensure that all surfaces adjacent to the window bonding flange are masked to prevent them from coming into contact with any primer or sealant. (v) Using isopropyl alcohol, solvent clean fuselage bonding flange. (Refer to 20-30) (w) Verify all required materials are present and all parts have been prepared and pre-fit. (x) Wearing clean gloves, lightly dampen a cloth with primer. Fold the cloth in such a manner to eliminate raw edges to reduce the possibility of lint. (y) Apply primer to the acrylic bonding flange. Wipe the cloth over the prepared area. Apply as little primer as possible while still wetting the entire surface. Keep primed area clean and free from contaminates while primer is drying. Seal window as soon as practical after primer drying period to minimize contamination. (z) (aa) ow the primer to dry for thirty to sixty minutes. Mix sealant per manufacturer's instructions. Mix the required quantity in the ratio specified in the adhesive manufacturer's instructions. (Refer to 20-10) Page 8
Do not apply sealant to window bonding flange. The sealant must be applied to the fuselage bonding flange. (ab) Apply a thin layer of sealant to the outer edge of the fuselage bonding flange. Spread the sealant out using an application spatula. (Refer to 20-10) When spreading the sealant, ensure all air pockets are removed. If more than one bead is required, apply it immediately adjacent to the prior bead to form one large bead. (ac) Directly on top of the sealant previously spread, apply a 1/4-inch to 3/8-inch bead of sealant down the center of the bond area. (Refer to 20-10) Five or more padded cargo rods may be necessary to hold the window into the proper position. Padded cargo rods may be placed on each corner of the window and in the center of the window. Additional padded cargo rods may be required to prevent the window from sliding down. (ad) (ae) Using padded cargo rods, secure the window into position making sure the reference marks made earlier are perfectly aligned and that the contour of the window matches the contour of the fuselage. Using a 1-inch application spatula, push sealant into the gap between the window and the fuselage. (Refer to 20-10) To prevent sealant from becoming damaged, pull tape towards sealant while the sealant is still damp. (af) Remove masking tape and fine line tape from the perimeter of the window and the fuselage. Overheating windshield can cause window damage. (ag) ow the sealant to air dry. Following the manufacturer s instructions, the sealant can be heat cured using a heat gun. (ah) Remove cargo rods. (ai) Remove the drop cloth. (aj) Using a vacuum cleaner, remove all debris. (ak) Install and secure interior trim panels. (Refer to 25-10) (al) Clean window. (Refer to 56-10) Page 9
WINDOW BONDING FLANGE SEALANT FUSELAGE (REF) SECTION FINE LINE TAPE 2" MASKING TAPE SEALANT FUSELAGE WINDOW OPENING FINE LINE TAPE 2" MASKING TAPE DIRECTIONAL ARROW WINDOW BONDING FLANGE HANDLE Trim window as required to ensure equal spacing on all sides NOTE Remove approximately 2-inches of protective coating. Make alignment marks to ensure proper alignment after fit up. Remove surface gloss from bonding flange using 80-grit sandpaper. Force the sealant into the bonding flange to ensure no air is trapped in the sealant. SR20_MM56_4352 Page 10 Figure 3 Window Installation