US airlines face a combined bill of nearly $120 million to replace the air intake cowl and related structure on 332 Boeing 757-200/300s in US registry.
The changes could become mandatory if a notice of proposed rulemaking being issued tomorrow by the Federal Aviation Administration becomes an airworthiness directive.
The FAA says it received reports that the 535EX cowls on the 757s Rolls-Royce RB211 turbofan engines developed "extensive cracking", the notice says. The cracks were found throughout the cowling, including the forward bulkhead web, web stiffeners, attachment fittings and thermal anti-ice spray ring assemblies, the FAA adds.
The cracks were traced to metal fatigue in the components, the FAA says.
The cowlings must be replaced to prevent components from the cowling to separate from the engine, which could then strike "critical" airplane control surfaces, damage the engine or hurt people on the ground, the FAA says.
If the airworthiness directive is issued, the FAA estimates the cost of compliance to be up to $60 million for replacing each of the two air intake cowlings on every 757 in US registry. The estimate assumes the job will require 252 work hours on each cowling priced at $85 per hour, plus $21,420 for replacement parts.
Such an airworthiness directive would immediately affect US 757 operators, including Allegiant, American, Delta, FedEx, United, UPS and US Airways, according to the Flightglobal Ascend Online database.