The Federal Aviation Administration is proposing shorter compliance times and additional records checks for Boeing 787 vertical-fin corrosion inspections.
The proposal would replace portions of a 2022 airworthiness directive for specified 787-8, 787-9 and 787-10 airplanes. Comments are due Sept. 28; the requirements are not yet a new final mandate.
FAA says later inspection reports found corrosion that was sometimes more severe than expected. It also determined that optional sealant types allowed by the existing directive may not provide enough working time to complete all bolt installations without damaging the seal.
The affected area includes 16 vertical-fin tension-bolt holes in the aluminum crown frame, composite deck and root fittings. Depending on aircraft history and configuration, work can include records review, detailed inspections, sealant and finish application, bolt and barrel-nut replacement, repairs and maintenance-program revisions.
FAA estimates that 116 U.S.-registered airplanes would be affected. For the inspection, sealant application and bolt or nut installation action, it estimates six labor hours plus $37,750 in parts, or $38,260 per airplane.
Applied across the U.S. fleet, that action could cost up to $4,438,160, according to the proposal. Separate records reviews are estimated at $85 per airplane, while FAA estimates an average 90 hours, or $7,650, per operator for a maintenance-program revision.
Those figures are regulatory estimates, not invoices for every operator. Actual work depends on prior maintenance, configuration, findings and any approved alternative method of compliance.
The unsafe condition described by FAA is undetected corrosion that could reduce structural integrity of the vertical fin and lead to loss of control. The agency will review comments before deciding whether to adopt, change or withdraw the proposal.