The National Transportation Safety Board (NTSB) has determined that improper maintenance during a brake system modification led to an American Airlines Boeing 737-800 overrunning a runway at Dallas/Fort Worth last year.
According to the final report released Friday, the Feb. 10, 2024, incident occurred when Flight 1632 from Washington’s Reagan National landed on Runway 17L and experienced a loss of braking effectiveness.
According to a summary of the aircraft’s cockpit voice recorder published by the NTSB, both pilots tried braking during the landing rollout.
The captain asked the first officer, “Do you got any brakes on your side?” The first officer responded, “No.”
The aircraft came to a stop in the paved overrun area, and all 104 passengers and crew members exited without injury.
Investigators found that maintenance personnel had mistakenly swapped the flexible hydraulic hoses connected to the right main landing gear brakes during a recent conversion from steel to carbon brakes. In addition, the wiring harnesses for the left main landing gear wheel speed transducers were cross-connected, meaning the system’s anti-skid functions were reversed on both sides of the aircraft.
The misconnection prevented the anti-skid system from properly releasing pressure on skidding wheels, causing the outboard tires to fail and extending the airplane’s stopping distance beyond the runway.
‘Improper Maintenance’
The NTSB concluded the probable cause was “improper maintenance due to human error during a braking system modification,” with a contributing factor being “the lack of a functional check to verify the flexible hydraulic hoses and transducer wiring were connected correctly.”
The brake modification, completed four days before the incident at American’s Tulsa maintenance base, replaced the aircraft’s steel brakes with carbon brakes and installed new flow limiters per a Boeing service bulletin.
Six mechanics, each with more than 30 years of experience, worked on the task. One later stated he believed the hoses were installed correctly at the time.
Following the event, the carrier revised its engineering order to require mechanics to label hydraulic hoses before removal and have an inspector verify proper reconnection. The airline also incorporated an operational test to detect swapped hoses or transducer wiring, inspected its entire 737 fleet, and updated maintenance manuals to prevent similar errors.
Boeing has since issued multiple service bulletins and fleet advisories reminding operators of the risks of crossed hydraulic or electrical connections during brake modifications. The manufacturer’s new guidance adds labeling requirements and procedural checks for maintenance personnel.
