BOEING 737-9UNITED AIRLINES INC

This analysis discusses the incorrect runway landing at Pittsburgh International Airport involving United Airlines flight 2627. The airplane had been cleared to land on runway 28C, but the flight crew aligned the airplane with and landed on parallel runway 28L. The flight crewmembers reported that, before beginning the descent into the terminal area, the first officer (the pilot monitoring) programmed the flight management computer (FMC) for the area navigation (RNAV) approach to runway 28C. During the descent, the crew was instructed twice by PIT approach control to change the landing runway. The crew was first instructed to expect a visual approach to runway 32; a short time later, the crew was provided vectors for the visual approach to runway 28C. Once on the base leg of the approach, the crew reported that the airport was in sight, and the controller cleared the airplane for the visual approach to runway 28C. The captain (the pilot flying) stated he visually acquired the precision approach path indicator (PAPI) lights. Runways 28C and 28L both had PAPI lights located on the left side of the respective runway. The captain stated that he observed one set of PAPI lights, which he thought were associated with runway 28C. The captain requested that the first officer extend the centerline of the approach from the next waypoint, at which time the first officer reported that both FMC control display units had blanked, taking away the backup lateral and vertical navigational guidance to runway 28C. Although the PAPI lights provided vertical guidance, the first officer attempted to diagnose and restore the FMC's lateral guidance, which created a distraction at a critical phase of the flight that reduced the crew’s opportunity to ensure correct runway alignment. A postincident review of FMC data showed that the FMCs experienced a dual reset when the airplane was at an altitude of about 4,000 ft (3,350 ft above ground level). The FMCs rebooted and began transmitting valid data 23 seconds later when the airplane was about 3,128 ft above ground level, about 4 minutes away from touchdown. While on final approach, the crew requested that the controller confirm that the airplane was cleared to land on runway 28C; the controller provided this confirmation. However, at some point afterward, the controller observed that the airplane was aligned with runway 28L. After verifying that no conflicting traffic existed, the controller decided to allow the flight to continue and land on runway 28L rather than issue a go-around instruction at a low altitude. This flexibility is permitted by Federal Aviation Administration Order 7110.65Z, which allows controllers to exercise their best judgment if they encounter situations not covered by the order. The flight crew subsequently aligned the airplane with and landed on parallel runway 28L, which was located about 1,200 ft to the left of intended runway 28C. Because runway 28L and runway 28C were closely located, it would have been challenging for the controller to have visually detected the misalignment. The crew stated that, after the airplane landed, the first officer rechecked the automatic terminal information service broadcast, and they thought that it indicated that the PAPI lights for runway 28L were out of service. However, a review of the broadcast revealed that the PAPI lights for runway 10L were out of service. The dual FMC reset was due to an issue with the system’s software, which was known before the incident. A fix was identified and released about 1 month before the incident. The dual blanking of the FMC control display units did not cause the flight crew to align the airplane with and land on the wrong runway given that the airplane was operating in visual meteorological conditions and the flight was cleared for the visual approach to runway 28C. Although the incident airplane had a runway awareness and advisory system (RAAS) installed in the cockpit, the operator did not select the option to provide crews with an aural alert for the runway that the airplane would be approaching in flight. If the operator had selected this option, the system would have alerted the incident flight crew that the airplane was aligned with a runway that was not consistent with the landing clearance provided by air traffic control, which might have precluded the wrong runway landing.