The Federal Aviation Administration is preparing to require airlines to inspect fuel nozzles on some Pratt & Whitney PW4000 engines in response to several engine fires.
The agency has written two proposed rules addressing the risk, including one that would require engines be inspected before further flights.
The proposals mark the FAA's response to reports of fuel nozzle manifold cracks in some PW4000 engines, and to several instances of fuel leaks and PW4000 engine fires.
The rule targets several PW4000 variants that power Airbus A300s, A330-200s and A330-300s, according to Flight Fleets Analyzer.
It applies to 186 engines in service with US airlines, though some 600 such engines are in service worldwide, Fleets Analyzer shows. American Airlines, Delta Air Lines, FedEx and UPS Airlines operate PW4000 variants named by the FAA.
"This [directive] was prompted by several reports of high cycle fatigue cracks in the fuel nozzle supply manifold," says one of two proposed rules.
"Thermal mechanical fatigue due to high thermal gradients" caused the cracks, it adds. "This condition, if not addressed, could result in engine fire, damage to the engine, and damage to the airplane."
P&W did not immediately respond to a request for comment. The company already issued related service bulletins, the FAA's documents say.
Inspections and parts replacement could cost airlines about $500,000 per engine, the FAA estimates. The agency is accepting comments from industry for 45 days.
The documents do not describe the specific events that prompted the proposed rule.
But earlier this year Nigerian investigators said they were looking at fuel nozzle leaks as a possible factor related to a PW4000 engine fire. That fire happened on a Delta A330-200 taking off from Lagos in March.