Leaky Toilet Breaks Boeing 767 Autopilot
A water leak inside of an aircraft lavatory may seem like a minor inconvenience to some passengers, but in reality, it can have serious consequences for the safe operation of the aircraft. A recent incident involving a Delta Airlines Boeing 767 has shed light on the importance of proper maintenance and the potential dangers of seemingly minor issues. The Boeing 767 is a wide-body jet aircraft that is commonly used for long-haul flights, such as transatlantic routes. According to a report released by the National Transportation Safety Board (NTSB), a water leak in the lavatory of the aircraft led to a disruption in pilot control during a flight from Prague, Czechia to New York City.
The flight crew reported experiencing roll control difficulties after being informed of a water leak emanating from the two mid cabin lavatories. While one lavatory was leaking water from under the lower right side of the toilet onto the floor, the other was leaking water from on top of the filter canister under the sink. The water supply was subsequently shut off and the lavatories were locked or left open for toilet use only. The crew cleaned up as much excess water from the floor as possible.
However, shortly after the water leak was reported, an AUTOPILOT caution message was displayed on the engine indicating and crew alerting system (EICAS) screen, along with an audible annunciation. The first officer disengaged and reengaged the autopilot several times, but the caution messages and audible indication persisted, and the aircraft made no lateral course corrections. The first officer was unable to move his control wheel to the left more than a couple of degrees of deflection and was thus unable to input the needed corrections. The captain then took control of the airplane but confirmed the same issue.
Image by G J Whitby from Pixabay
The flight crew declared an emergency and was given clearance to descend to 9,000 ft where the temperature was above freezing. As the airplane descended through 12,000 ft, a minor “jolt” was felt by the flight crew, after which the control wheel operated normally, and the flight continued to and landed safely at JFK. A review of flight data by Boeing revealed evidence of a temporary restriction in the lateral control system, starting shortly before the initial disconnect of the center autopilot.
Image by Bruno /Germany from Pixabay
The investigation revealed that the cause of the disruption was likely ice formation due to the open drain mast heater circuit breakers (CBs), located in the electronic equipment bay. Although there were no current or previous maintenance write-ups on these heaters, Delta removed and replaced them as a precaution. Delta Air Lines reported that before the incident, the airplane was out of service for maintenance which required pulling the forward and aft lavatory drain mast heater CB’s. It is possible that these CBs were inadvertently left open when the airplane was returned to service on June 23, 2022.
In conclusion, the incident underscores the need for careful maintenance procedures and vigilance when addressing seemingly minor issues. The NTSB report serves as a reminder to airlines and aviation authorities to take every precaution to ensure the safety of passengers and crew.