FAA Mandates Boeing 737 MAX Spoiler Wire Checks

DALLAS — The Federal Aviation Administration (FAA) has issued an airworthiness directive (AD) for the Boeing 737-8, 737-9, and 8-200 models to address potential issues with their spoiler wire bundles. 

As per the AD, improper installation of these wire bundles could lead to unintended spoiler movement, increasing the risk of a "hardover" event, where a control surface moves to its structural limit, potentially compromising the aircraft's control.

The directive emphasizes the FAA's ongoing oversight of Boeing 737 MAX safety concerns, reinforcing the importance of precise inspections to prevent potentially catastrophic incidents.

Key Incident

The AD follows a December 2021 incident involving a Boeing 737-8 that rolled 30 degrees to the right due to spoiler malfunctions.

Pilots observed a “SPOILERS” warning light but encountered difficulties referencing the issue in the flight manual. Though the aircraft landed safely, the spoiler "hardover" scenario had been noted in the plane's logbook days earlier.

A spoiler hardover scenario occurs when a spoiler on an aircraft moves to its extreme position, or "hard limit," without proper control input. Spoilers are surfaces on the wings that reduce lift and assist with roll control or braking. In a hardover, unintended or incorrect positioning of the spoiler can:

• Compromise control: If a spoiler on one wing deploys fully without an opposing action on the other wing, it can create an imbalance, potentially causing the aircraft to roll unexpectedly.
• Stress pilot response: Pilots must quickly counteract the motion using ailerons or other controls to maintain stable flight.
• Increase risks: If multiple spoilers on the same wing experience hardover, it may exceed the lateral control capabilities of the aircraft, leading to a potential loss of control.

This condition can arise from mechanical failure, wiring issues, or software anomalies, making proper installation and maintenance of spoiler systems critical for safety.

Findings, Requirements

The FAA identified improper clearance in spoiler wire bundles could lead to damage and unintended motion. A hardover affecting more than one spoiler on the same wing could surpass lateral control capabilities, posing a significant safety hazard.

Operators must inspect and adjust the spoiler wire bundle clearance, ensuring proper spacing to prevent chafing or damage. Boeing's guidance specifies minimum clearances between the bundles, clamps, and adjacent structures.

While many stakeholders supported the directive, some urged faster compliance timelines, including SunExpress and the Foundation for Aviation Safety. However, the FAA determined that a shorter timeline was unnecessary after a risk analysis revealed no immediate danger.