TASK 53-11-37-600-810
8. Upper Lobe Frames, Stringers and Skin - Corrosion Prevention
Figure 207
A. General
(1) The fuselage is of semimonocoque construction which uses 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 at
the same time with the fuselage structure.
(2) Cracks were found in the areas where the skin and doubler come apart. Cracks come from the
fastener holes in the double rivet row in Stringer 17L and 17R between BS 422 to 500A, and
BS 727A to BS 747.
(3) Broken attach bolts were found in the vertical-fin-aft-spar-terminal support fitting at the upper
center part of BS 1088 bulkhead. The attach bolts are made from H-11 steel alloy which are
susceptible to cracks caused by stress corrosion.
(4) The main compartment sidewall insulation have pillow blankets installed just inboard of the
airplane skin and insulation blankets installed inboard of the pillow blankets. It was found that
the pillow catches the moisture against the airplane skin which can add to possible corrosion of
the adjacent structure.
(5) 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
51-00-59 STANDARD PREVENTIVE MAINTENANCE PROCEDURES
C. Consumable Materials
Reference Description Specification
C00259 Coating - Chemical And Solvent Resistant
Finish, Corrosion Inhibiting Primer
BMS10-11 Type I
D. Location Zones
Zone Area
200 Upper Half of Fuselage
E. Corrosion Prevention
SUBTASK 53-11-37-610-055
(1) The basic corrosion prevention philosophy is to make the periodic inspection described in
INSPECTION AND DETECTION, SUBJECT 51-00-51 to preclude or detect the early stages of
corrosion. Skin bulges, missing fasteners or white powdery deposits are evidences of the
existence of corrosion which should alert operators that some corrective action is required. A
corrosion prevention program should be initiated to prevent the accumulation of moisture or
corrosive compounds in order to minimize the occurrence of corrosion.
SUBTASK 53-11-37-610-056
(2) Where extensive corrosion exists (very noticeable skin bulges, missing fasteners, or large
amounts of white deposits at the fastener heads or faying surfaces), refer to Structural Repair
Manual for details of corrosion removal.
737-600/700/800/900
AIRCRAFT MAINTENANCE MANUAL
53-11-37
Page 241
D633A101-ILF Oct 15/2015
ECCN 9E991 BOEING PROPRIETARY - Copyright © Unpublished Work - See title page for details
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