Regulators from the US Federal Aviation Administration are requiring operators of Pratt & Whitney PW4000 powerplants to inspect engines with certain "number three bearing oil pressure tubes" for cracks or repairs to prevent oil fires, failure of high-pressure turbine discs, uncontained engine failures and general aircraft damage.
The FAA says in a new airworthiness directive that the action was prompted from one report of a bearing that cracked and caused an engine in-flight shutdown, one incidence of a test cell event and seven reports since 2007 of the repaired number three bearing oil pressure tubes cracking, which led to unscheduled engine removals.
Estimates offered by FAA show that 973 engines installed on US aircraft would need the one-time, "10min" visual inspections. The FAA calculates that once the tube is removed, required parts should cost roughly $9,000, and labour rates would average $85 an hour.
Overall, complying with the new rulemaking would cost US operators $8.9 million.
Operators are required to perform the inspection for either cracks or repairs and remove any number three bearing that has been repaired. After the rule's 28 December effective date, operators are prohibited from installing the affected number three bearing oil pressure tubes into any engine.