Operators of more than 300 newer Boeing 737s—including nearly half of the in-service MAXs—will be ordered to inspect slat tracks and remove parts identified as being from a batch that may not meet Boeing’s production requirements, the FAA and the company said June 2.
"One batch of slat tracks with specific lot numbers produced by a supplier was found to have a potential non-conformance,” Boeing said. It did not name the supplier.
"The affected parts may be susceptible to premature failure or cracks resulting from the improper manufacturing process,” the FAA said.
The suspect slats have not been linked to any in-service issues.
Boeing has identified a subset of 179 MAXs and 133 NGs that may have parts from the non-conforming batch. Among these aircraft, the suspect parts are “most likely" installed on 20 737 MAXs and 21 737 NGs that Boeing has targeted, but operators will be asked to inspect all 312 aircraft as a precaution.
Boeing is developing a service bulletin that recommends affected operators perform the checks and replace any slats identified as being from the batch within 10 days. The FAA said it will mandate the bulletin with a final airworthiness directive (AD) that will be effective immediately, bypassing the notice-and-public-comment period that many ADs follow. FAA’s directive will apply to 55 U.S.-registered aircraft: 33 MAXs and 32 NGs. The directive is likely to be adopted worldwide, however.
Boeing said the work “should take one to two days” per aircraft. Boeing is “staging replacement parts at customer bases” to minimize aircraft downtime, it added.
While most FAA ADs follow a notice-and-comment period, immediately-effective directives are used from time to time to address more pressing issues. The 10-day compliance window recommended by Boeing is aggressive, particularly for a problem that requires a parts replacement—as opposed to a procedural change or manual update, for instance—and has not been linked to any in-service incidents.
Complying with the directive will be easy for the MAX fleet, as it remains grounded following two fatal accidents in five months. Affected NGs may have to be pulled from service to accomplish the work.