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Issued: December 01, 2010 26-56-001 Page 1 of 12
SERVICE BULLETIN SA26 SERIES Windows Inspection of Cockpit Heated Windshields (P/N 26-21126)
1. PLANNING INFORMATION A. Effectivity:
All SA26 Series Aircraft B. Reason:
Over a 2.5 year calendar period, the window manufacturer and repair facility has repaired 19 windows with inner glass ply fracture. The manufacturer deems inner glass ply failure as critical to the structural integrity of the window.
C. Description:
This service bulletin implements repetitive inspections on heated glass windshields (P/N 26-21126) and if noted damage is found, replacing the affected window.The inspections defined in this service bulletin are intended to identify glass shear and / or interlayer cracking that may be present in the windshield assembly. These inspections are focused on the areas adjacent to the windshield metal insert with particular attention to areas not directly adjacent to the windshield heating grid. (See Figures 2 and 3) D. Compliance:
Mandatory E. Approval:
FAA Approved for Engineering Design.
F. Manpower:
M7 Aerospace estimates 2 manhours (1 manhour per window) to accomplish this service bulletin. This estimate is for direct labor only accomplished by an experienced crew. Adjust the estimate with operator task hour data if necessary.
G. Material-Cost and Availability:
(1) Cost:
Because of pricing fluctuations, individual cost estimates should be obtained from your normal material procurement outlet.
(2) Availability:
Not applicable.
Issued: December 01, 2010 26-56-001 Page 2 of 12
SERVICE BULLETIN SA26 SERIES H. Tooling-Price and Availability:
Not applicable I . Weight and Balance:
Not affected J. Reference:
None NOTE: References are for manufacturers’ use only.
K. Other Publications Affected:
SA26 Series Maintenance Manual.
2. ACCOMPLISHMENT INSTRUCTIONS A. Perform inspections in 2.B. in accordance with intervals called out in Table 001.
B. Inspection:
(1) Determine Time in Service of the LH and RH cockpit heated windshields.
(2) With the use of maintenance stands or ladders, obtain adequate access to perform a detailed visual inspection of the entire periphery of the LH and RH cockpit heated windshields from the outside of the aircraft.
(3) Clean the inner and outer surfaces of the LH and RH cockpit heated windshields per step 4.J. Ensure that the surface of the glass is free from dirt, oil, or other contaminants.
(4) With the use of a flashlight and 10X magnification, perform a detailed visual examination of the inner glass ply, the interlayer, and the outer glass ply in an area defined by the inner edge of the metal insert (see Figure 3) and extending inward
3.0 inches toward the center of the windshield. Inspect for indications of delamination, interlayer cracking, moisture ingress, and / or glass shear. The viewing angle for the inspection should extend from a line of sight that is perpendicular to the surface of the glass to an angle extending approximately 45 degrees to either side of this plane as shown in Figure 5.
(5) For indications of delamination, adhere to the limits and take appropriate action as defined in step 3.
(6) For indications of glass shear or interlayer cracking, the windshield must be repaired / replaced by an FAA approved vendor prior to further flight.
Issued: December 01, 2010 26-56-001 Page 3 of 12
SERVICE BULLETIN SA26 SERIES
(7) For removal and installation instructions for heated windshields refer to step 4.
C. Complete aircraft records according to 14 CFR 43.9.
D. Complete and mail Service Bulletin compliance form.
3. DEFINITIONS AND ACCEPTANCE CRITERIA - WINDSHIELDS A. Definitions Critical The viewing area of the windshield used for taxiing, takeoff, climb, cruise, and landing.
Semi-Critical The viewing area of the windshield used for general flight vision.
Delamination Delamination - The disbonding of either the inner and / or the outer glass component from the adjacent interlayer material. It appears as a clear bubble that is flat and smooth with a circular or irregular shape.
Glass Shear A fracturing of portions of the glass material adjacent to the interlayer material. It can extend to significant areas of failure parallel to the glass surface. Glass shear can be similar in appearance to delamination, but can be differentiated from delamination by "rainbow" B 1100 to 5000 3 weeks from publish Every 100 hours *TIS until date of SB. window reaches category C.
C Greater than 5000 3 weeks from publish Every 50 hours *TIS.
date of SB.
Category Hours *TIS on each Threshold Inspection Repetitive Inspection date/ new or repaired date/time (on or before) time (on or before) windshield A Less than 1100 3 weeks from publish Every 150 hours *TIS until date of SB. window reaches category B.
THRESHOLD/REPETITIVE INSPECTION INTERVALS FOR 26-21126 HEATED WINDSHIELDS TABLE 001 * TIME IN SERVICE
Issued: December 01, 2010 26-56-001 Page 4 of 12
SERVICE BULLETIN SA26 SERIES colors, distinct shear planes and crushed contours displayed as a white "frosting" in appearance. Inspection for glass shear can be aided by the use of and LED type flashlight, particularly in highlighting the "rainbow" colors associated with glass shear.
Interlayer CrackingA narrow break, fissure, or separation in the interlayer material.
Interlayer cracking normally occurs adjacent to the glass components along the inboard edge of the metal insert and also at the interlayer release boundary. When viewed from the edge of the crack (see Figure 4), interlayer cracking is indicated as a prominent black line type crack / tear through the thickness of the interlayer. When viewed looking at the plane of the crack (see Figure 4), striations in the interlayer can be observed.
B. Critical Area Inspection – Glass Windshields NOTE: The critical area is the area of the laminated glass windshields used for taxiing, takeoff, climb, cruise, and landing measured 2.0 in (50.8 mm) from inner edge of retainer, around entire periphery towards center of windshield, except measured 0.5 in (12.7 mm) around the temperature sensors.
(1) Delamination
(a) Cloudy or milky appearance in the delamination indicates moisture or solvent penetration. Windshields with this condition should be replaced at the earliest opportunity.
(b) Delaminated areas characterized by irregular or jagged boundaries indicate uneven separation of the vinyl and glass.
(c) Replace windshield if one of the following conditions are noted:
1 Area of vision required for safe operation is affected (pilot's discretion).
2 Windshield heat system inoperative.
(2) Glass Shear
(a) Glass Shear in any portion of the windshield requires replacement prior to further flight.
(3) Interlayer Cracking
(a) Interlayer Cracking in any portion of the windshield requires replacement prior to further flight.
C. Semi-Critical Area Inspection – Glass Windshield NOTE: Semi-Critical areas are the perimeter of the glass windshield, within the 2.0 in
(50.8 mm) region from the inner edge of the retainer.
(1) Delamination
(a) Cloudy or milky appearance in the delamination indicates moisture or solvent penetration.
(b) Delamination areas characterized by irregular or jagged boundaries indicate uneven separation of the vinyl and glass.
Issued: December 01, 2010 26-56-001 Page 5 of 12
SERVICE BULLETIN SA26 SERIES
(c) Replace windshield if one of the following conditions is noted:
1 Area of vision required for safe operation is affected (pilot's discretion).
2 Windshield heat system inoperative.
(2) Glass Shear
(a) Glass Shear in any portion of the windshield requires replacement prior to further flight.
(3) Interlayer Cracking
(a) Interlayer Cracking in any portion of the windshield requires replacement prior to further flight.
4. REMOVAL/INSTALLATION – HEATED WINDSHIELD A. Removal – Heated Windshield
(1) Remove instrument panel glareshield.
(2) Remove interior panels and covers.
(3) Remove windshield mounting screws.
(4) Remove panel and cover clips.
NOTE: Mark location of clips for reference during windshield installation.
(5) Remove inner fasteners.
(6) Remove wiring from windshield.
(7) Remove windshield by pushing panel outward.
(8) If windshield sealant does not release after pushing panel outward, proceed as follows:
(a) Cut through sealant around outer edges of windshield with sharp-bladed instrument.
(b) Spray Ram Chemicals Aerosol Mold Release 225 (or equivalent) into crevices made from cutting around outer edges of windshield.
WARNING: WEAR EYE PROTECTION AND GLOVES, WHEN USING SAFETY WIRE TO CUT WINDSHIELD SEALANT.
(9) If windshield sealant will not release after cutting and spray application of mold release agent, proceed as follows:
(a) Dig a small hole in sealer and push through a length of 0.020 inch (0.51 mm) thick stainless steel safety wire.
(b) Wrap ends of wire around a screwdriver or similar tool.
Issued: December 01, 2010 26-56-001 Page 6 of 12
SERVICE BULLETIN SA26 SERIES
(c) With one person inside and another outside, pull wire in a reciprocating motion through sealer until windshield is free. Remove windshield.
(10) Clean all sealant residue from windshield frame with methyl propyl ketone (MPK).
B. Installation – Heated Windshield NOTE: The following procedures apply to all heated window installations, using either reusable existing heated windshields or new heated windshield panel with required drilling, trimming, counterboring, countersinking, and deburring completed IAW paragraphs 4., E. through H., this section.
(1) Inspect heated windshield panel for distortion and defects; mask windshield for protection.
(2) Check flatness of windshield supporting structure, and maintain a maximum of 0.030 inch (0.762 mm) gap between windshield and faying surface of airframe structure. Maximum gap may be maintained by bonding shims to frame with EC1838 structural adhesive.
(3) Apply thin coat of MIL-S-8802 sealant (or approved equivalent sealant) to aircraft windshield frame.
NOTE: MIL-S-8802 sealant may also be used as an underlay material to fill a minor mismatch of heated windshield with surrounding aircraft windshield frame.
MIL-S-81733 sealants are approved equivalents for MIL-S-8802 sealant.
Ram Chemicals Aerosal Mold Release #225 may be used as a release agent between windshield(s) and sealing compound to facilitate removal of window(s).
(4) Apply approximately 0.188 inch (4.775 mm) thickness of MIL-S-8802 sealant (or equivalent) to each corner of windshield frame.
(5) Position windshield into aircraft mounting structure. Ensure a minimum gap of
0.030 in (0.762 mm) between windshield glass and aircraft mounting structure.
(6) Apply a small amount of MIL-S-8802 sealant (or equivalent) around each screw prior to installing into screw holes.
(7) Install screws just snug, and allow sealant to set.
(8) Stage-torque screws 15 to 20 inch-pounds (1.69 to 2.26 N·m), using a cross sequence tightening schedule (e.g., 12 o'clock to 6 o'clock, 3 o'clock to 9 o'clock, 5 o'clock to 11 o'clock, etc.).
NOTE: Do not exceed the suggested minimum torque values during initial tightening.
(9) Install interior panel and cover clips.
(10) Install all inner retainers.
(11) Tighten inner retainer screws hand tight, then loosen one-quarter (1/4) turn, using a cross sequence tightening schedule.
(12) Install wiring to electro-thermal windshield.
Issued: December 01, 2010 26-56-001 Page 7 of 12
SERVICE BULLETIN SA26 SERIES
(13) Install heated windshield panels and covers.
(14) Fill spaces between windshield and aircraft primary structure with sealant.
(15) After sealant has cured, remove all masking tape and clean windshield. Install glareshield.
C. Required Equipment
(1) Hand drill, high-speed, 15,000-25,000 RPM.
(2) Drill press, automatic constant feed.
(3) High-speed steel drill bit, 0.1935 inch.
(4) Counterbore bit, 0.313 inch with 0.031 inch radius and 0.1935 inch pilot.
(5) Countersink bit, 0.1935 inch.
(6) Torque wrench.
(7) Steel rule.
(8) Rasp.
(9) Sheet metal Cleco fasteners or draw mono-locks.
(10) China marker.
(11) Spacers, aluminum.
(12) Sealant, MIL-S-8802, or the following approved equivalent:
(a) Sealant, MIL-S-81733.
D. Preparation
(1) Inspect new windshield for general condition. Mask for protection.
E. Drilling and Trimming – Heated Windshield
(1) Position new windshield in place in the aircraft primary structure.
(2) Determine amount of trimming required for proper fit.
NOTE: Approximately 0.063 inch (1.600 mm) space should be allowed for sealing between the outer edges of the new windshield frame and the aircraft primary structure.
(3) Trim new windshield frame as required with rasp. Do not contact windshield glass with rasp.
(4) With new windshield held firmly in place, and using the aircraft primary structure retainer as reference, drill three (3) 0.190 - 0.194 in (4.826 - 4.928 mm) holes, one
(1) hole at top and one (1) at each side of windshield frame.
NOTE: Drill holes from cockpit side of frame.
(5) Remove windshield and place it on a flat work area with inner side down. Place old windshield, inner side down, on top of new windshield.
Issued: December 01, 2010 26-56-001 Page 8 of 12
SERVICE BULLETIN SA26 SERIES
(6) Align old windshield with new windshield, securing windshields together with bolts and nuts through holes in new windshield frame.
(7) Use old windshield as a template guide, and drill remaining holes through new windshield frame.
NOTE: Drill holes on a drill press to help ensure proper alignment.
F. Counterboring – Heated Windshield
(1) Place new windshield on drill press with inner side facing up. Adjust drill press to counterbore a maximum depth of 0.192 - 0.196 in (4.877 - 4.978 mm) into frame.
(2) Counterbore all holes with 0.313 inch counterbore bit with 0.031 inch radius and a 0.1935 inch pilot.
G. Countersinking – Heated Windshield (Figure 1)
(1) Place new windshield on drill press with outer side facing up.
(2) Countersink all holes using a 0.1935 inch countersink.
NOTE: Countersink must have an included angle of 100° and produce the degree of flushness required with retaining screws installed.
Countersinking Heated Windshield Figure 1 H. Deburring
(1) Remove chips and burrs on both sides of the windshield frame.
I. Installing Spacers
(1) Ensure spacers are installed flush.
J. Cleaning
(1) Remove masking tape.
(2) Remove dirt and other substances from glass surface with clean water.
0.188 INCH
(4.775 MM)
0.371 - 0.383 INCH
(9.423 - 9.728 MM) NAS43DD3-12 SPACER 6M561000201
OUTER FRAME (ALUMINUM)
VINYL INTERLAYER
INTER FRAME (ALUMINUM )
PLASTIC GASKET
Issued: December 01, 2010 26-56-001 Page 9 of 12
SERVICE BULLETIN SA26 SERIES
(3) Wash with mild soap and water or a 50/50 solution of isopropyl alcohol and water.
Do not use any abrasive materials or any strong acids or alkalines. When wiping the surface, use a soft cloth or sponge and use a straight rubbing motion.
(4) Rinse thoroughly and dry; do not apply wax.
Issued: December 01, 2010 26-56-001 Page 10 of 12
SERVICE BULLETIN SA26 SERIES Heating Grid Outer Edge of Windshield & Metal Insert Metal Insert Inner Edge View Looking Forward at RHS Windshield
COCKPIT HEATED WINDSHIELD FIGURE 2
COCKPIT HEATED WINDSHIELD COMPONENTS FIGURE 3
Outer glass Inner glass Interlayer Metal Retainer Metal Insert Inner Edge of Metal Insert Sealant
3.0 inch
Issued: December 01, 2010 26-56-001 Page 11 of 12
SERVICE BULLETIN SA26 SERIES
INTERLAYER CRACKING FIGURE 4
Outer glass Inner glass Interlayer Metal Retainer Metal Insert When viewed from edge, crack appears as a black line or a series of short disconnected black lines Interlayer crack
Outer glass Inner glass Interlayer Metal Retainer Metal Insert When viewed from side, striations are visibleInterlayer crack
Issued: December 01, 2010 26-56-001 Page 12 of 12
SERVICE BULLETIN SA26 SERIES
Outer glass Inner glass Interlayer Metal Retainer Metal Insert Plane perpendicular to plane of glass 45º45º Extent of viewing angle for inspection