What happened
On the morning of 8 February 2022, a serious aircraft proximity incident occurred at Lanseria International Aerodrome (FALA). A McDonnell Douglas DC3-TP67, registration ZS-ASN, was performing a simulated GNSS approach for Runway 07 after a local flight. Simultaneously, a Boeing 737-800, registration ZS-ZWF, was inbound from King Shaka International Aerodrome and requested a visual approach for the same runway.
As the two aircraft progressed toward the threshold, the faster 737-800 closed the distance on the slower DC3-TP67. This resulted in a significant loss of separation, with the aircraft coming within approximately 500 feet vertically and 68.7 meters laterally of each other. Both crews received Traffic Collision Avoidance System (TCAS) Resolution Advisories (RA) and successfully maneuvered to avoid a collision.
The investigation
The SACAA AIID investigation focused on the air traffic control (ATC) instructions and the communication between the tower and the flight crews. Investigators examined the sequence of clearances, noting that the air traffic control officer (ATCO) had cleared both aircraft for approaches on the same runway without providing specific traffic information to the lead aircraft.
Furthermore, the investigation scrutinized the radio telephony exchange, specifically a speed restriction instruction issued to the 737-800. While the pilot acknowledged the clearance, they failed to read back the specific instruction to reduce to the minimum safe approach speed, and the ATCO did not identify this omission.
Findings
- The primary cause was that the ATCO permitted two aircraft to use the same runway for visual approaches without warning them of each other's proximity, allowing the faster aircraft to catch the slower one.
- The instructions provided to ZS-ASN were issued too late and lacked necessary traffic information.
- The pilot of ZS-ZWF failed to read back the speed reduction instruction, and the ATCO did not verify the acknowledgment.
- The ATCO's situational awareness was compromised by a high workload, as 12 aircraft were under their jurisdiction at the time of the incident.
- The two aircraft were operating under conflicting reporting points, with one instructed to report at 6nm and the other at 5nm on the same path.
Safety action
Following the incident, the Air Navigation Service Provider (ANSP) conducted safety discussion sessions to share lessons learned and briefed the ATCO on improved planning and prioritization techniques. The ATCO involved was also provided with Critical Incident Stress Management (CISM) support.