(2)
Position faceplate or window in window frame immediately after application of the fairing compound. Press the faceplate gently against the window frame until high spots on the window frame are in contact with the faceplate.
CAUTION: STEPS (1) THRU (5) MUST BE COMPLETED DURING THE APPLICATION TIME OF THE COMPOUND - REFER TO TABLE I.
(3)
Apply a sample bead of compound, from batch used in step (A), to a piece of scrap metal and set aside to cure under the same atmospheric conditions.
NOTE: To accelerate curing of compound, circulate warm air, not to exceed 1200F (460C), over the compound and metal surfaces.
(4)
Install every third or fourth bolt and tighten bolts enough to hold the faceplate in position. Compound should extrude from all points around faying surface being repaired.
CAUTION: DO NOT OVERTIGHTEN BOLTS AND WARP FACEPLATE OR WINDOW FRAME, BECAUSE SPRINGBACK MAY NECESSITATE FURTHER FAIRING.
(5)
Remove excess compound, from boltholes by inserting bolts, and from around frame with spatula or wedge shaped wooden block.
(6)
Remove the faceplate after the time shown under “Release from Mold” in Table I. TABLE I
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APPLICATION TIME AND CURE RATE
Material Temperature (OF) (OC) Application Time (Hrs) Release From Mold (Hrs) Sandable (Hrs) Full Cure (Hrs)
Tereco 175 M 75 士5 120 士5 24 士3 46 士3 3 N.A. 24 2.5 48 5 240 24
EC 3587 -1/4 75 士5 120 士5 24 士3 46 士3 .25 N.A. 2 1 4 2 48 *[1] 20
EC 3587 -1 75 士5 120 士5 24 士3 46 士3 1 N.A. 8 2 16 4 96 *[1] 30
NOTE: N.A. = Not Applicable
*[1] Shore A reading of 90 (min.) 5 second reading.
NOTE: If the appropriate hardness testing equipment is not available, it can be sufficient to check that the sample compound is “tack free,” or hard enough not to adhere to the finger when touched. This check is important. If flight is allowed with a window installed on fairing compound of which large areas are wet, cabin pressure may cause leaks around the window edge.
(7)
Trim excess compound from window frame.
(8)
Fill any voids in excess of 0.01 inch diameter with additional compound and allow it to harden.
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WINDOW NO. 1 - REMOVAL/INSTALLATION
1. General
A. The number 1 window (windshield) is pressure sealed on installation by means of a gasket like, molded-in-place rubber seal. The beaded silicone rubber seal surface mates with the window frame to ensure an effective pressure and moisture tight seal around window (Fig. 401). On windows without Z-channel strip, the rubber pressure seal is molded to windshield glass. A bumper strip is an integral part of pressure seal and provides protection against chipping edge of glass and moisture penetration. On windows with Z-channel strip, the pressure seal is an integral part of the window assembly and in combination with a formed stainless steel Z-channel strip, is bonded to periphery of windshield glass.
CAUTION: DO NOT ATTEMPT TO REMOVE Z-CHANNEL STRIP FROM WINDSHIELD GLASS, DOING SO WILL DISTURB INTEGRITY OF PRESSURE SEAL.
B. Fairing compound is applied to the window frame and its purpose is to accommodate the irregularities in the frame surface, ensuring that a perfectly flat surface is presented to the windowpane. The thickness of the compound varies: at high spots on the window frame there is no compound.
C. Also shown on Fig. 401 are some items which are not components of the pressure seal. They are:
(1)
Aerodynamic Smoother. Aerodynamic smoother is installed in the gap between the window frame and the edge of the bumper strip and provides aerodynamic flushness and protection against water entrapment. A nylon cord or nylon thread is installed under the aerodynamic smoother to facilitate its removal when required.
(2)
O-rings. Ethylene propylene 0-rings are installed under the nut washers except on the fasteners where seal washers are installed (Ref par. 1.C.(3)). The 0-rings are allowed to compress a predetermined amount thereby transmitting sufficient compression load into the window assembly to compress the seal bead to make a weather seal. On fasteners adjacent to windshield heat terminals, colored silicone rubber O-rings, being nonconductive, are preferred to ethylene propylene rings. No clearance with terminal is required when using nonconductive O-rings. Rubber O-rings may also be used in place of ethylene propylene O-rings at other locations if desired.
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