FAA Proposed Airworthiness Directive: Boeing 737 Thrust Reverser Locking Actuator Safety

The FAA is proposing a new airworthiness directive (AD) targeting all Boeing 737 variants including the -600, -700, -700C, -800, -900, and -900ER series. The directive was triggered by a report revealing that adjusting the upper locking hydraulic actuator proximity sensor targets using certain aircraft maintenance manual (AMM) procedures can produce incorrect actuator status indications. Specifically, the thrust reverser may falsely indicate a 'locked' status when it is in fact not locked — a potentially catastrophic in-flight safety hazard. To address this unsafe condition, the proposed AD would require operators to conduct measurements, functional tests, and operational checks of the upper locking hydraulic actuator. If deficiencies are found during these checks, applicable on-condition corrective actions must be performed. Additionally, the AD mandates a revision to existing maintenance or inspection programs to incorporate specific Certification Maintenance Requirements (CMRs). These CMRs ensure that the thrust reverser locking system is verified at defined intervals, preventing the faulty sensor condition from going undetected. This is a proposed rule at this stage, meaning it is open for public comment before finalization. Once finalized, compliance would be mandatory for all operators of the affected Boeing 737 models operating under FAA jurisdiction.

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