OPS21LA003

The blocked go-around radio instruction from the air traffic control tower to the arrival aircraft which resulted in the arrival aircraft continuing the landing approach. This led to a loss of separation between the landing aircraft and the aircraft awaiting departure on the runway. Contributing to the loss of separation was the controller’s distraction communicating with a helicopter transitioning the airspace.

On June 10, 2021, about 1745 Pacific Daylight Time (PDT) a runway incursion occurred at the San Diego international airport when a SkyWest flight was positioned on Runway 27 for takeoff at the same time a Southwest flight was cleared to land on the same runway. The SkyWest flight was instructed to Line Up and Wait (LUAW) on Runway 27. According to FAA recordings, the Southwest flight was instructed to go around on an approximate 0.84-mile final (about 1.2 miles from the runway 27 displaced threshold); however, the transmission was blocked and the instruction was not heard by the crew. The air traffic control tower controller instructed the SkyWest flight to exit the runway at taxiway C2 about 11 seconds prior to instructing the Southwest flight to go around and to not overfly the SkyWest airplane. The Southwest flight maneuvered around the SkyWest flight exiting the runway and subsequently landed on Runway 27. The closest proximity was 0.18 miles laterally and 200 feet vertically. A review of the FAA audio recordings indicated that the tower controller informed the Southwest flight that there would be traffic holding in position for takeoff on the runway following a preceding arrival aircraft. The controller then issued instructions to other uninvolved aircraft, including a helicopter that was transitioning the airspace. Just after the controller issued instructions for the SkyWest flight to exit the runway, and when the Southwest flight was on an approximate 1.2-mile final, the ASDE-X provided a mandatory go-around alert, and the controller issued go-around instructions to Southwest. The Southwest flight subsequently maneuvered and offset to the left of Runway 27, and then back to the right, and the aircraft aligned with and landed on Runway 27. The SkyWest crew did not hear the air traffic controller’s transmission to the Southwest flight to go around. The SkyWest crew reported they did hear the Southwest flightcrew’s query about the airplane on the runway. According to the FAA, the tower controller was communicating with a helicopter transitioning the airspace after they had instructed SkyWest to LUAW. This additional communication likely distracted the controller from monitoring the position of the SkyWest and Southwest airplanes. Although the FAA reported that tower communication was working normally at the time of the event, they were requested to conduct testing on the strength of the radio signal from the tower cab at various distances away from the airport. However, there was no indication that the FAA was able to conduct such testing and therefore it could not be conclusively determined if the control tower’s frequency strength was adequate to overpower an airborne aircraft’s transmission for other aircraft operating on the airport. Therefore, it is likely that the air traffic controller and the Southwest flightcrew’s simultaneous transmissions canceled each other with no indication to the controller, the arriving aircraft, nor any other aircraft on the frequency.

On February 2, 2021, Southwest Airlines produced a Flight Safety Alert for SAN, specifically for runway 27 approaches. The alert stated that data indicate a potential for “unstable approaches” and “GPWS Terrain/Obstacle Warnings.” It further provided conditions that may result in an unstabilized approach with those conditions being “a steeper glidepath,” “Parking garage approximately 0.4 NM from RWY 27 threshold” and “high gross weight and tailwinds may require vertical speeds in excess of 1000 fpm during final approach segment.” Southwest Airlines General Approach Policies The Southwest Airlines B737NG Operating Manual, Section 11.1.3.1 provided, in part, the following general approach guidance: If available, follow glidepath guidance on final. Use at least one of the following, if available: • Electronic glideslope (ILS) • Glidepath from an RNAV approach in the FMC navigation database • Visual glideslope Pilots may fly slightly above the glidepath for wake turbulence avoidance during visual approaches. (PF) Prior to the final approach segment, position hands and feet on the aircraft controls when the autopilot is engaged and flaps are extended for maneuvering or approach. (PM) Prior to the final approach segment, position hands and feet to immediately assume control of the aircraft if circumstances warrant. Go-Around/Missed Approach The Southwest Airlines B737NG Operating Manual, Section 11.5.1 provided the following guidance: The Pilot Flying must execute a go-around/missed approach if any of the following occur: • Any Flight Deck Crew Member directs or calls for a go-around. • ATC directs a go-around. • The approach does not meet stabilized approach criteria. • The CDI exceeds a 2-dot deflection while on the FAS in IMC. • The expanded LOC pointer becomes "unfilled" while on the FAS in IMC. • A 2-dot low glideslope deflection on the FAS in IMC is exceeded. • The VOR pointer exceeds 10° from the desired course on a VOR approach inside the FAF in IMC. • Sufficient visual references for landing are not present and any of the following occur: - (ILS) Radio Altitude display flashes and turns amber. - The aircraft altimeter indicates that the DA or DOA is reached. - The missed approach point, if applicable, is reached. • The Pilot initially has sufficient visual references but then loses them below DA, ODA, or MDA. • A landing in the touchdown zone cannot be safely accomplished. Note: The touchdown zone is the area of the runway 500 ft to 3,000 ft beyond the landing threshold not to exceed the first one-third of the usable length beyond the threshold. • The aircraft touches down beyond 1,500 ft with an insufficient PWB System-computed stopping margin. • Before reaching DA, DDA, or MDA, any required portion of ground equipment/system elements become inoperative, unless adequate and appropriate backup exists for the type of approach being flown. • An HGS malfunction occurs during an HGS approach and adequate runway visual references have not been established. • An APCH WARN or HGs FAIL occurs and the Captain does not have the runway in sight (actual runway is in sight, not just part of the runway environment, such as lead-in lights or other approach lights). • For CAT Ill operations, if any controlling RVR is reported below the lowest authorized minima. • During an RNAV (RNP) or RNAV (GPS) approach, when a visual approach cannot be accomplished: - From the IAF to the MAP. o Lateral Navigation Performance Scale ANP bar amber indication or o NPS pointer cannot be maintained at less than 1 x RNP (NPS full scale deflection). o Both Pilots' primary altimeters differ by more than 100 ft at the FAF. o FMC Alert message UNABLE REQD NAV PERF-RNP appears. o Dual FMC failure. o Dual CDU failure. o Dual GPS failure. o Loss of MAP display. o Autopilot failure with RNP less than 0.30 NM. - From the FAF to the MAP, unless a safer course of action can be taken. o If any required aircraft equipment fails o Vertical Navigation Performance Scale pointer cannot be maintained between the ANP bar limits. o The following FMC alert messages appear: FMC DISAGREE or any VERIFY POS alerting message. · For a Predictive Windshear (PWS) caution or warning. On approach, initiate a normal go-around. Be prepared to execute a windshear recovery. · For a Ground Proximity Warning System (GPWS) warning or caution: - Warning-Any time, immediately initiate the Terrain Avoidance Maneuver. - Caution-On approach, initiate a go-around in any of the following situations: o At night o In IMC o If unable to acquire terrain visually Stabilized Approach Criteria The Southwest Airlines, Flight Operations Manual, dated July 23, 2020, Section 11.1.1 “Stabilized Approach Criteria – All Approaches” provided the following guidance: Good landings start with a stabilized approach. Southwest Airlines uses the following criteria for stabilized approaches. Significant speed and configuration changes during an approach complicate aircraft control, increase the difficulty of safely evaluating an approach as it progresses, and complicate the decision at the decision point (i.e., DA, DDA, MDA). Assess the probable success of an approach before reaching the decision point. This requires both Pilots to determine that the requirements for a stabilized approach have been met and are being maintained. Comply with the following stabilized criteria for all approaches. Deviations within normal limit criteria are acceptable for operational conditions. The intention is that the PF completes a stabilized final approach entry by 1,000 ft above touchdown zone elevation (TDZE). Above 1,000 ft, PMs should make necessary informative callouts to assist the PF to achieve stabilized conditions by 1,000 ft above TDZE. Momentary deviations of glidepath, course, airspeed, and sink rate do not require an immediate go-around. Make required deviation callouts. • By 1,000 ft above TDZE, the aircraft must be in the planned landing configuration (landing gear down and landing flaps). For approaches flown in vertical speed, the aircraft must be in the planned landing configuration by the final approach segment. • By 1,000 ft above TDZE, the aircraft must be in the VTARGET speed range. VTARGET speed range is VTARGET + 10 and -5 kt. The PF should clearly communicate adjustments for an updated wind report from tower. • By 1,000 ft above TDZE, the aircraft must be on appropriate glidepath with a normal descent rate. Maintain a stable approach path. Normal glidepath descent rate is 700-800 fpm. Final approach segments with glidepaths greater than 3° and/or high groundspeeds may require a sustained descent rate in excess of 1,000 fpm. This is acceptable as long as this condition is briefed and all other stabilized approach criteria are met. Use 1,000 fpm maximum for normal maneuvering during visual, circling, non-precision, and sidestep approaches. This directive does not restrict Pilots from flying slightly above the glidepath for wake turbulence avoidance during visual approaches. • For approaches where maneuvering is required, the aircraft is on and maintaining final approach course or runway centerline with wings essentially level by 500 ft above TDZE. The intention is for Pilots to comply with the configuration, speed, descent rate, and checklist requirements by 1,000 ft above TDZE, and then continue necessary maneuvering to be essentially wings level by 500 ft above TDZE. Some charted approach procedures may require a turn below 500 ft. Once established, stabilized approach criteria must be maintained throughout the rest of the approach. If stabilized approach criteria are not met, execute or direct a go-around/missed approach. It is the duty and responsibility of any Flight Deck Crew Member to execute or direct a go-around/missed approach when the stabilized approach criteria are not met. Additionally