DL2196 - Incident: Delta B739 at Atlanta on Nov 29th 2017

A Delta Airlines Boeing 737-900, registration N852DN performing flight DL-2196 from Indianapolis,IN to Atlanta,GA (USA), was on final approach to runway 09R cleared to land on runway 09R, when tower instructed the aircraft to go around from low height, the crew initiated a go around. Tower subsequently explained it appeared they were over the taxiway. The aircraft positioned for another approach to Atlanta and landed safely on runway 10 about 15 minutes later.

The NTSB reported the aircraft was aligned with the runway center line initially, however, during short final about 1nm before the runway threshold began to veer left and lined up for the taxiway N parallel to the runway. The taxiway was occupied. The aircraft went around from about 100 feet AGL already past the begin of the taxiway. The NTSB reported cloud tops were at 300 feet AGL. Both crew members reported that they were right of the runway center line on an ILS approach, the localizer showed a full deflection indicating they were right of the runway. The captain reported he called the go around at decision height (200 feet AGL) because he couldn't see the runway or airport environment, the first officer also reported they called for and initiated the go around before the air traffic controller instructed the go around. The flight data recorder was read out, first results suggest that the autopilot was disconnected at 1200 feet AGL at a heading of 100 degrees, the autothrottle was disengaged at 500 feet AGL. At about 400 feet the heading changed briefly to 81 degrees, then the aircraft turned to 87 degrees, during that time the aircraft descended from 400 to 100 feet AGL, at 100 feet the pitch changed from 2 degrees to 8 degrees, the aircraft turned right to about 105 degrees. The minimum altitude was recorded at 60 feet AGL.

The airline reported they are cooperating with the investigation. The aircraft was initially right of the center line, the crew corrected but obviously overcorrected. The first officer was pilot flying and the captain pilot monitoring.

On May 10th 2022 the NTSB released their final report concluding the probable causes of the incident were:

The flight crewmembers’ failure to properly monitor the airplane’s flightpath, which caused the approach to become unstabilized and resulted in the airplane’s descent below the decision altitude while misaligned with the localizer course. Contributing to the incident were the first officer’s delay in setting go-around thrust after the captain called for the go-around and the captain’s failure to take control of the airplane after go-around thrust was not immediately set, both of which caused the airplane to come within about 50 ft vertically of an occupied taxiway.

The NTSB analysed:

The flight crew was conducting an instrument landing system approach to runway 9R. When the airplane was about 3.5 miles from the runway threshold and at an altitude of about 1,230 ft above ground level (agl), the first officer (the pilot flying) disconnected the autopilot, after which the airplane began to deviate to the right of the localizer course. When the airplane was at an altitude of about 500 ft agl, the first officer disconnected the autothrottle; at 300 ft agl, he began correcting to the left to return to the center of the localizer course. When the airplane reached the decision altitude (200 ft agl), the airplane was drifting toward the taxiway N extended centerline, which was parallel to, and about 650 ft to the left of, the runway 9R centerline.

Radar data indicated that the airplane was 1 mile from the runway 9R threshold at the time that the airplane aligned with taxiway N. When the airplane was at an altitude of 120 ft agl and was 600 ft to the left of the runway 9R centerline and 50 ft to the right of the taxiway N centerline, the first officer initiated a go-around after the captain’s (the monitoring pilot) command. The airplane descended to about 50 ft above the western end of the taxiway before it began to climb. Engine power increased while the airplane was above and aligned with taxiway N. The airplane was then vectored for an instrument landing system approach for runway 10. The flight crew subsequently landed the airplane uneventfully.

Another airplane (a Boeing MD-88) was taxiing westbound on taxiway N at the time of the incident approach. According to radar data, the airplanes, at their closest distances, were separated by 286 ft horizontally and 257 ft vertically.

The approach became unstabilized when the first officer improperly adjusted the airplane’s heading and flew outside of the localizer course. The airline’s procedures indicated that an approach would be considered to be stabilized if it maintained, among other things, a “lateral flight path while in the landing configuration.” The manual warned that, if a stabilized approach could not be established and maintained, pilots were to initiate a go-around and not attempt to land from an unstable approach. Also, the airline’s procedures indicated that an approach should not continue below the decision altitude (200 ft agl in this case) unless “the aircraft is in a position from which a normal approach to the runway of intended landing can be made.” Thus, the flight crew’s actions were not consistent with company procedures.

Further, when the airplane reached the decision altitude for the approach, the flight crew failed to call for a go-around and execute, in a timely manner, the initial steps for a go-around. Specifically, flight data recorder data showed that the takeoff/go-around switch was not selected until 4 seconds after the airplane reached the decision altitude and that a total of 12 seconds elapsed between the time that the airplane reached the decision altitude and the thrust lever began advancing toward go-around power. These delays caused the airplane to descend about 150 ft below decision altitude and come within about 50 ft of an occupied taxiway.

The 1052 hourly weather observation for the destination airport indicated, among other conditions, 1/8 mile visibility, mist, patches of fog, and an overcast ceiling at 300 ft agl. The flight crewmembers received this observation about 1057 (9 minutes before the incident). Thus, the crewmembers were provided with sufficient information to understand the weather conditions that the flight would encounter during the approach to the airport.

The captain and the first officer reported no history of sleep disorders, and a review of their sleep histories revealed that they received adequate rest during the 3 days preceding the incident. Further, sleep opportunities for the captain and first officer were aligned with local nighttime, so circadian disruptions were not an issue. Thus, the captain and the first officer were not likely experiencing fatigue during the incident flight.

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