Maintenance Practices

1 FAA Aviation Safety SPECIAL AIRWORTHINESS INFORMATION BULLETIN SUBJ: Maintenance Practices SAIB: NM-17-10 Date: April 13, 2017 This is information only. Recommendations aren’t mandatory.

Introduction

This Special Airworthiness Information Bulletin (SAIB) advises registered owners, operators and maintenance personnel of The Boeing Company Model 737, 747, 757, 767 and 777 airplanes of procedural changes for detecting corrosion damage to the aft fuselage structure in the area of the vacuum waste tanks.

At this time, the airworthiness concern is not an unsafe condition that would warrant airworthiness directive (AD) action under Title 14 of the Code of Federal Regulations (14 CFR) part 39.

Background

We have received numerous reports of corrosion damage to the aft fuselage structure in the area of the vacuum waste tanks on Model 777 airplanes. This corrosion has been attributed to insufficient clean up and neutralization of leakage and spillage from the vacuum waste system. These reports document that an initial finding of corrosion damage is often followed within the year by corrosion found in close proximity. The waste material from a vacuum waste system spill or leak is acidic and corrosive to the airplane structure, such as skin, stringers, and frames. The waste material erodes the corrosion inhibiting compound and the protective finishes, which causes areas of bare structure that are more susceptible to corrosion.

While the reports of corrosion have been limited to Model 777 airplanes, Boeing believes the Model 737, 747, 757, and 767 airplanes are subject to the same issue. To minimize and address this corrosion, Boeing is revising the related aircraft maintenance manuals (AMMs) and structural repair manuals (SRMs), as listed in Table 1 of this SAIB. The revisions include adding procedures for neutralizing vacuum waste; defining the correct procedures for containing, cleaning, and neutralizing vacuum waste; and adding procedures for the inspection for and removal of corrosion, and re-application of protective coatings.

Recommendation

The FAA recommends that all owners and operators of the affected airplanes incorporate the revised AMM and SRM procedures when they become available. The planned release dates are included in Table 1 of this SAIB.

For Further Information Contact

Julie Moon, Aerospace Engineer, Cabin Safety and Environmental Systems Branch, ANM-150S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue SW., Renton, WA 98057-3356; telephone: 425-917-6427; fax: 425-917-6590; email: [email protected].

2 Table 1