The US FAA wants operators of more than 1,000 next generation Boeing 737s to begin periodic inspections of the twinjet's thrust reverser assemblies.
The proposed airworthiness directive (AD), to be issued on 22 March, was prompted by reports of damage to the attachment fittings for thrust reverser actuators of in-service aircraft. Damage is caused when bushings in the actuator attach fitting wear out due to friction during the normal course of operations.
"We are proposing this AD to detect and correct such damage, which could result in actuator attach fitting failure, loss of the thrust reverser auto re-stow function, and consequent loss of control of the airplane," says the agency. "Loss of the thrust reverser auto re-stow function removes one of the three primary levels of protection against an uncommanded thrust reverser deployment."
While certain aircraft must get a one-time inspection of hydraulic actuator ends within 7,500h of the finalised AD, all aircraft must have repetitive detailed inspections of thrust reverser mechanisms every 7,500 flight hours under the proposal.
The FAA estimates the AD will apply to 1,070 US-registered 737-600/700/700C/800/900 and 900ER-series aircraft, collectively costing an estimated $2 million for the one-time inspections and $2 million for each 7,500 flight hour inspection.