FRAMES AND BULKHEADS CORROSION PREVENTION - MAINTENANCE PRACTICES
1. General
A. This procedure contains 7 tasks:
(1) Corrosion Prevention of the Crown Frames, Stringers and Skin.
(2) Corrosion Prevention of the Lower Lobe Structure.
(3) Corrosion Prevention of the Galley and Lavatory Areas.
(4) Corrosion Prevention of the Main Gear Wheel Well and Keel Beam.
(5) Corrosion Prevention of the Nose Gear Wheel Well.
(6) Corrosion Prevention of the Door Openings.
(7) Corrosion Prevention of the Upper Lobe Frames, Stringers and Skin.
TASK 53-11-37-600-811
2. Crown Frames, Stringers and Skin - Corrosion Prevention
Figure 201
A. General
(1) The fuselage is of semi monocoque construction utilizing aluminum skins, circumferential
frames and longitudinal hat section stringers. The fuselage skin is installed with circumferential
butt joints and longitudinal lap joints that are usually flush riveted. Skins should be treated
concurrently with fuselage structure.
(2) The stringers, frames and skins have been found susceptible to corrosion due to moisture
entrapment between the skin and insulation blankets. Added to this moisture spillage,
condensation or moisture through open doors running along frames or stringers collecting at
some dammed location contribute to corrosion. Corrosion can readily start where protective
finishes have been broken or deteriorated.
(3) Treatment of the interior structure should be accomplished at the same time as longitudinal lap
splices are treated or whenever access is gained to expose the frame/stringer/skin structure.
For lap splices, refer to INSPECTION AND DETECTION, SUBJECT 51-00-51.
(4) Insulation blankets are provided on cabin interiors for passenger comfort and to minimize the
condensation of warm cabin air on cold skins and stringers. Corrosion has been experienced in
areas where the blankets are not installed taut and wrap around stringers or lay on the skins.
Reports of water soaked blankets have been common in these instances.
(5) Delamination of the waffle doublers on the crown and side skin panels has been reported. If
left untreated, delaminated doublers may promote corrosion and cracking of the skin interior
and doublers.
(6) Stress corrosion has been attributed to reported three cracks in the right side BS540 bulkhead
forging refer to Figure 201 (Sheet 1).
(7) Refer to CORROSION PREVENTION, SECTION 51-00 of this manual for a discussion of the
Aging Airplane Corrosion Prevention and Control Program and related documentation.
Structural items within this section are subject to the unique requirements of the mandatory
Corrosion Prevention and Control Program.
B. References
Reference Title
51-00 CORROSION PREVENTION
51-00-51 INSPECTION AND DETECTION
737-600/700/800/900
AIRCRAFT MAINTENANCE MANUAL
53-11-37
Page 201
D633A101-ILF Jun 15/2016
ECCN 9E991 BOEING PROPRIETARY - Copyright © Unpublished Work - See title page for details
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