This One's on American Airlines Maintenance, Not Boeing

[PHXPhlyer]

A braking system 'anomaly' caused an American Airlines jet to exceed a Dallas runway, NTSB says

https://finance.yahoo.com/news/braking- ... 06904.html

An American Airlines jetliner that suffered an “anomaly” in the braking system before running past the end of a runway in Texas last month had undergone a brake-replacement job four days earlier, U.S. investigators said Thursday.

An inspection showed that flexible hydraulic lines to parts of the braking system on the Boeing 737 had been improperly reconnected, the National Transportation Safety Board said in a preliminary report on the Feb. 10 incident at Dallas-Fort Worth International Airport.

American said in a statement that it is cooperating with investigators and safety is the airline’s top priority.

The NTSB said that within moments of the plane touching down on the runway, the automatic brakes went from off to on and then off again. The pilots used brake pedals and thrust reversers to slow down, but as the plane neared the end of the runway, the captain of American flight 1632 warned air traffic controllers.

“Total brake failure. We are departing the end of runway 17L (for left). Roll crash fire rescue,” the captain said.

The plane came to rest on a paved area beyond the runway. The 104 passengers and crew members were bused to the terminal.

The NTSB said that four days before the runway incident, American replaced steel brakes on the main landing gears with carbon brakes and wheel assemblies, based on 2016 instructions from Boeing.

The work required disconnecting flexible hydraulic hoses and reconnecting them. An inspection following the event on the Dallas runway showed that two of the lines “had been improperly reconnected” after the brake job, according to the preliminary report.

Wiring to one of the main landing gears also had been installed incorrectly, the NTSB said.

The safety board said its investigation was continuing.

The plane was built in 2009. It is an earlier version of the Boeing 737 than the Max.

More details from AvHeraald:

https://avherald.com/h?article=514d2f9f&opt=0

Incident: American B738 at Dallas on Feb 10th 2024, overran runway on landing
By Simon Hradecky, created Sunday, Feb 11th 2024 18:43Z, last updated Thursday, Mar 21st 2024 18:56Z

An American Airlines Boeing 737-800, registration N991AN performing flight AA-1632 from Washington National,DC to Dallas Ft. Worth,TX (USA) with 98 passengers and 6 crew, landed on Fort Worth's runway 17L at 19:42L (01:42Z Feb 11th) but came to a stop only on the runway end safety area past the runway end. There were no injuries and no damage. The aircraft was towed to the apron about 90 minutes after landing.

According to ADS-B data the aircraft touched down in the runway's touch down zone about 520 meters down the runway at 152 knots over ground and at 600 feet MSL (according to standard pressure, Dallas Ft. Worth runways' elevations are about 600 feet MSL) and began deceleration, the aircraft slowed through 132 knots over ground about 990 meters down the runway (at 600 feet MSL) and slowed through 90 knots about 1580 meters down the runway (at 600 feet MSL), only then the aircraft's transponder began to indicate the aircraft was on the ground. The aircraft slowed through 40 knots over ground about 2460 meters down the runway and about 110 meters before the runway end, crossed the runway end at 27 knots over ground and came to a stop about 23 meters past the runway end on the paved surface of the runway end safety area.

According to local witnesses three main tyres deflated.

The FAA reported the aircraft went into the runway end safety area after experiencing a braking malfunction. The FAA have opened an investigation.

On Mar 21st 2024 the NTSB released their preliminary report summarizing the sequence of events:

The first officer (FO) was the pilot flying and the captain was the pilot monitoring. In a postincident statement, the flight crew reported that an instrument landing system (ILS) approach to runway 17L was flown with the airplane configured with the flaps at 30° and the autobrakes selected to 3 due to a reported tailwind of one knot. They stated that the approach and touchdown were normal with no directional control issues noted. Shortly after touchdown, the flight crew observed the AUTOBRAKE DISARM light illuminate and the brakes did not engage requiring manual braking by applying pressure to the pedals while deploying the thrust reversers.

The flight crew stated that the airplane began to decelerate with the thrust reversers but at a slower pace. The FO indicated that the brakes were not working correctly. When approaching taxiway Q7, the ground speed was higher than expected and the captain stated, “my aircraft” and the FO responded, “your aircraft.” The FO called 60 knots and the captain noticed no decrease in ground speed. The captain indicated that he immediately moved both thrust reverser levers to their maximum reverse position. When the speed was about 40 to 50 knots and about 1,000 from the end of the runway the captain called DFW tower, “American 1632, total brake failure, we are departing the end of runway 17L, roll crash fire rescue.” Passing the runway threshold lights, the captain felt the airplane come to a stop a short time later.

...

Data from the digital flight data recorder (DFDR) was sent to the NTSB’s Vehicle Recorder Laboratory in Washington, DC, for analysis.A preliminary data review has been completed and a plot showing the braking parameters is shown in figure 2. Data showed that at touchdown the auto brake applied [Auto Brk Applied] parameter momentarily (less than 2 seconds) transitioned from “No Auto Brk” to “Auto Brk” and then back to “No Auto Brk” for the remainder of the landing rollout. The left and right brake pressure increased to their maximum pressure consistent with normal (manual) braking. Data also showed the engine 1 and 2 thrust reverser parameters [Eng1 and Eng2 TR Dply-DEU] transitioned from “stowed” to “deployed” about 8 seconds after touchdown. They remained deployed for about 12 seconds, were stowed for about 6 seconds, and then re-deployed for the remainder of the landing rollout.

The cockpit voice recorder (CVR) was removed from the airplane and sent to the NTSB’s Vehicle Recorder Laboratory in Washington, DC, for analysis.

...

Analysis of the ADS-B and DFDR data shows that the left and right main landing gear (MLG) touched down about 1,500 feet from the runway threshold and the nose landing gear came down just after 2,000 feet. Groundspeed on the initial touchdown was 150 knots and 140 knots for the nose. The aircraft departed the end of the runway surface at 30 kts.

...

Post-incident troubleshooting and inspection of the brake control system found the flexible hydraulic lines going to the number 3 (right inboard) and number 4 (right outboard) MLG brakes had been improperly re-connected after the carbon brake/flow limiter installation. The flexible hydraulic lines supplying pressure to the number 3 and 4 MLG brakes had been swapped at the connection with the flow limiters.

System troubleshooting also found a discrepancy with the wiring to the left MLG wheel speed transducers. During a wheel speed transducer operational test, maintenance found the wiring harness, located in the left MLG axle, had been installed incorrectly. The electrical connector for the number 1 (left outboard) and the number 2 (left inboard) wheel speed transducer were swapped.


PP

[Dushan]