LAX04IA302

Asiana Airlines flight 204 (AAR204), a Boeing 747-400 that had been cleared to land on runway 24L, initiated a go-around and overflew Southwest Airlines flight 440 (SWA440), a Boeing 737 which had been cleared into position and hold for takeoff on runway 24L. Radar reconstruction of the event found that AAR204 passed over SWA440 at 200 feet during the go-around. At the time of the incident, a controller change for the LC2 position had just occurred and the relief controller was responsible for the air traffic control handling of both AAR204 and SWA440.

At 2151:21, the LC2 controller who was being relieved cleared AAR204 to land runway 24L. At this point, the Boeing 747 was 9.3 miles from the runway. About 2 minutes later, while AAR204 proceeded inbound on the approach, the LC2 controller provided a relief briefing to the LC2 relief controller and advised him that AAR204 was landing on runway 24L, which the relief controller acknowledged. After assuming the responsibility of the position, the first transmission from the LC2 relief controller was to SWA440 instructing the flight crew to taxi into position and hold on runway 24L. AAR204 was 1.81 miles from the runway at 700 feet. According to the SWA440 captain's statement, he saw the Asiana Boeing 747 on final approach but believed that the aircraft was landing on runway 24R. Twelve seconds later, the relief controller cleared SWA440 for takeoff. Radar data indicated AAR204 was 1.26 miles from the runway and about 35 seconds from reaching the landing threshold. Data retrieved from the SWA440's flight data recorder indicated the airplane was on taxiway V approaching runway 24L when given the takeoff clearance. This meant that the flight crew had less than 35 seconds to taxi on to runway 24L, begin a departure roll, and travel 6,000 feet before AAR440 crossed the landing threshold, which would be impossible. According to the Asiana captain's statement, he observed the Southwest Boeing 737 approaching runway 24L but believed the airplane would hold short of the runway. Once he recognized the aircraft was entering the runway, he initiated a go-around and estimated it was about the time his airplane was passing through 400 feet approaching the runway.

The relief controller said that contrary to the recorded relief briefing where he clearly acknowledged that AAR204 was cleared for the left runway, he fully believed AAR204 was landing runway 24R, and therefore, was unaware of the conflict. He first became aware of the problem when the Airport Movement Area Safety System (AMASS) generated an alarm. At this point, AAR440 was only about 12 seconds from colliding with SWA440, and without the prompt actions of the Asiana flight crew a collision would have likely occurred. When the relief controller recognized the problem, he canceled SWA440's takeoff clearance and AAR440's landing clearance. However, AAR204 had already overflown SWA440 on the go-around, clearing the aircraft by about 200 feet. Although the relief controller believed AAR204 was landing runway 24R, this did not alleviate his responsibility to properly monitor the operation and ensure separation was maintained.

Recorded voice communications of the position relief briefing indicated the LC2 controller informed the relief controller that the inboard runway (RWY 24L) was in use for landings, and that AAR204 was cleared to land on runway 24L. There was no indication from the relief controller that he did not understand or needed clarification from the relieving controller. The LC2 controller addressed all major areas on the LAX position relief checklist, and conveyed information accurately during the position relief briefing. About 30 seconds after the LC2 controller completed the briefing, he remembered additional information about helicopter operations and began relating that to the relief controller; however, this conversation was interrupted by another radio transmission, which effectively distracted both the LC2 controller and relief controller and likely exacerbated the difficulty the relief controller had in converting the briefing information in his short term memory to working memory. Immediately following the relief briefing, the LC2 controller left the postion.

Based on what is known about the volatility of information held in short term memory, and the speed of decay in short term memory without rehearsal of the information, it is not surprising that the relief controller failed to recall every detail LC2 controller's position relief briefing with complete accuracy. The relief controller was briefed on the location and clearances for seven aircraft (seven pieces of information is about the limit that can be effectively retained short term memory), but was not given sufficient opportunity to rehearse this information in working memory until 13 seconds after the briefing was completed. The format and timing of the position relief briefing and its interruption by routine radio transmissions contributed to the relief controller's memory error.

LAX tower controllers interviewed during the investigation stated that, because of the location of the tower, it was difficult to determine visually whether a single approaching aircraft was lined up for runway 24R or runway 24L. Controllers stated that destination runways were most difficult to determine visually for large aircraft, such as the Boeing 747. The LC2 relief controller believed this was the reason he did not recognize the conflict between AAR204 and SWA440. Although this may be true, it does not alleviate the controller of his responsibility to monitor the operation. In addition, the relief controller was aware the inboard runways were in use for landings and should have been alert to the possibility of aircraft arriving on runway 24L.

To assist the controllers with visual observations, the LAX tower is equipped with Digital Bright Radar Indicator Terminal Equipment (DBRITE) displays. The relief controller stated that he saw AAR204's radar target on the DBRITE display during the position relief briefing, but that he did not specifically recall seeing AAR204's data block. A review of the radar replay indicated AAR204's data block displayed two sets of alternating aircraft information: runway assignment and aircraft type were presented for 5 seconds; followed by a 15-second presentation of altitude and ground speed data. The relief controller stated that he glanced at his DBRITE display before the runway incursion. However, he clearly did not perceive the critical information that AAR204 was assigned to land on runway 24L, and he therefore did not take action to eliminate the conflict. Time-sharing of runway assignment information on the aircraft data tag increased the likelihood that critical information would not be perceived when parallel approaches were being conducted on the north side of the LAX tower.

LAX is equipped with (Airport Movement Area Safety System) AMASS, which is a computer software enhancement to the airport surface detection equipment. The LAX AMASS at the LC2 position generated an aural and visual alert only 12 seconds before a collision would have occurred, warning the controller to the impeding conflict; however, the flight crew of AAR204 had observed the Southwest Boeing 737 taxing towards the runway and, believing the aircraft was not going to stop, initiated a go-around before the AMASS alert activated. A collision was avoided, not by AMASS, but by the actions of the flight crew of AAR204.

At the time of the incursion, five certified professional controllers and one operations supervisor were working in the tower cab. According to facility personnel, there would normally be 10 people available to work on this shift but injuries and illness had reduced the available shift staff to five. It is common for ATC to combine positions to accommodate facility and/or operational needs. Controllers routi

1.1 History of flight

On August 19, 2004, about 1455 Pacific daylight time, an Asiana Airlines Boeing 747-400, HI7415, overflew a Southwest Airlines Boeing 737-7H4, N461WN, while the Southwest airplane was in position on the active runway 24L, at Los Angeles International Airport, Los Angeles, California. Southwest Airlines operated the Boeing 737 under the provisions of 14 CFR Part 121, and Asiana Airlines operated the Boeing 747 under the provisions of 14 CFR Part 129. There was no damage to either airplane nor injuries to the combined total of 417 passengers and 29 crewmembers. Visual meteorological conditions prevailed and an instrument flight plan had been filed.

On August 24th Southwest Airlines safety personnel reported to the National Transportation Safety Board investigator that the captain of Southwest flight 440 (SWA440) reported that an Asiana Boeing 747 (AAR204) came with in 200 feet of his airplane while it was executing a go-around on runway 24L. Southwest flight 440 had been cleared for takeoff on runway 24L. The captain stated that he became concerned when the Asiana airplane did not come in to his view, as it should have, when landing on the parallel runway 24R. He began to move his airplane off the runway when the Asiana airplane overflew his, coming within 200 feet. The captain of AAR204 stated that he and his copilot identified the runway conflict while they were on the short final approach for landing and executed a go-around about 400 feet above ground level (agl).

At 2151:21, the LAX local 2 (LC2) tower controller cleared AAR204 to land on runway 24L, and the flight crew acknowledged the landing clearance. AAR204 was conducting an ILS runway 24L approach and radar data indicated the aircraft was 9.3 miles east of the airport. About this time, the LAX operations supervisor on duty asked the local assist 1 (LA1) controller (hereafter referred to as the "LC2 relief controller") to relieve the LC2 controller, who needed a break.

At 2153:08, the LC2 controller began a position relief briefing for the LC2 relief controller. He stated, "Alright uh both runways available. Let's see you got the board you said. Got a lot of flow up there, a lot of flow. Better study up on that." The LC2 relief controller stated, "uh huh, I do I came from assist one." The LC2 controller continued, "Alright. They're on the boards, the inboards I should say, both runways available, PIREPs none, you can visual out. Uh, rolling out on the right is Southwest, cleared to land is Asiana on the left. Southwest on the pad is a LAXX I haven't tried to coordinate. You got a King Air, I'm sorry, he just left, so right now you're back to released. These two have been approved, but not run down or released…" The LC2 controller continued, "This one is awaiting approval," then stated, "and that's all I can think of." At 2153:43, the LC2 relief controller advised, "Alright well I've got it." The LC2 controller responded by saying, "Uh helicopters I'm sorry you have one more." The LC2 relief controller asked, "Oh and who is it?" As the LC2 controller began to say the helicopter's call sign, "Coast Guard six five...," he was interrupted by a transmission from a Southwest Airlines flight crew who had just landed runway 24R and requested permission to exit the runway at a different location than instructed. The LC2 controller approved the request, and after he received an acknowledgement from the Southwest crew, he continued briefing the LC2 relief controller.

At 2153:55, the LC2 controller completed the briefing by informing the LC2 relief controller of the Coast Guard helicopter's call sign and location on the airport, and that no other helicopters were operating in the vicinity of the airport. During the interview, the LC2 controller stated that at this time he unplugged his headset from the position and left to speak briefly with the supervisor about his break.

At 2154:06, the LC2 relief controller issued his first radio communication from the LC2 position, "Southwest four forty runway two four left position and hold." SWA440's flight crew acknowledged the instruction stating, "Position, and hold southwest four forty." At this time, AAR204 was 1.81 miles from the 24L runway threshold and the aircraft's altitude was 700 feet. According to the SWA440 Captain's statement, he turned onto taxiway V, which is perpendicular to runway 24L; he saw the Boeing 747 on final approach but believed the aircraft was landing on runway 24R.

The LC2 relief controller spent the next few seconds coordinating SWA440's southwesterly departure via the landline with the LAX local one (LC1) controller. At 2154:18, the LC2 relief controller stated, "Southwest four forty turn left heading two one zero runway two four left cleared for take off." The flight crew replied, "we'll turn two one zero cleared for takeoff runway two four left southwest four forty. AAR204 was 1.26 miles from the runway threshold and at 500 feet.

At 2154:26, the LC2 relief controller issued a wake turbulence advisory to the flight crew of UAL961, the lead aircraft on final approach to runway 24R and advised, "caution wake turbulence heavy seven forty seven short final." Radar data and recorded voice communications indicated UAL961 was not following any other aircraft to runway 24R. The wake turbulence advisory was in reference to AAR204 who was approximately 3 miles ahead of UAL961 but on final approach to runway 24L. The LC2 relief controller believed AAR204 was landing runway 24R, and therefore, a wake turbulence advisory would have been required.

At 2154:40, an aural and visual alert was generated by the Airport Movement Area Safety System (AMASS) at the LC2 position. AAR204 was .4 miles from the runway at 300 feet. At this time, recorded voice communications indicated the LC2 relief controller was issuing a landing clearance to Sky West 6040, the second aircraft on final approach to runway 24R. According to the Asiana captain's statement, he observed the Southwest B737 approaching runway 24L but believed the aircraft would hold short of the runway. Once he recognized the aircraft was entering the runway, he initiated a go-around and estimated it was about the time he was passing through 400 feet.

At 2154:48, a voice of unknown origin stated on the frequency, "is that four seven going around?" AAR204 was .18 miles from the runway at 200 feet.

At 2154:50, the LC2 relief controller advised the flight crew of SWA440, "cancel take off clearance hold in position." The flight crew responded by saying, "holding in position southwest four forty." The controller then instructed the flight crew of AAR204, "fly heading two five zero climb and maintain two thousand." The flight crew replied, "heading two five zero climb and maintain two thousand asiana two zero going around now." Radar data indicated AAR204 had flown over SWA440, clearing the aircraft by about 200 feet, and was now .32 miles past the runway threshold and climbing out of 500 feet.

At 2155:07, the flight crew of SWA440 advised the LC2 relief controller, "we're going to go to echo eight and come back southwest four forty." The LC2 relief controller approved the request and instructed the flight crew to taxi and hold short of runway 24L at the full length. Echo eight is a designated taxi way off of runway 24L.

At 2156:23, the flight crew of SWA440 asked the LC2 relief controller, "what happened up there sir." The controller replied, "well he apparently was lined up for the wrong runway." The flight crew responded by saying, "ok yeah the runways are so close together we looked at it and it was so big we thought he was on the right side as well." In response, the LC2 relief controller said, "yep, I did the exact same thing."

Upon hearing the AMASS alert, the operations supervisor who was located on the south side of the tower cab began walking to the north side of the