What happened
On 28 January 2001, two aircraft were operating within the Pretoria General Flying Area 1 near Freeway Aerodrome. The first aircraft, a Cessna 172 with registration ZS-LEX, was conducting a private training flight. The crew, consisting of an instructor and a student, departed from Wonderboom Aerodrome and received clearance to enter the general flying area via the south-eastern corner near the Ludwig rose farm. After transitioning to the local frequency, the student pilot provided a position report at 0854Z.
As the Cessna 172 approached Freeway Aerodrome at approximately 0857Z to begin flight exercises, a Pitts S-1S, registered as ZS-MEL, passed extremely close to the aircraft. The Pitts S-1S flew past the right wing of the Cessna 172 in a near-vertical climb, maintaining a distance of only about 10 to 20 meters from the wingtip.
The investigation
Investigators examined the accounts of both flight crews to determine the nature of the encounter. The instructor of the Cessna 172 attempted to contact the pilot of the Pitts S-1S regarding the maneuver. The pilot of the ZS-MEL initially denied performing an aerobatic maneuver, claiming to have maintained visual contact with the Cessna 172 throughout the encounter.
However, the pilot of the ZS-MEL provided a different account, stating that while flying toward Wonderboom, he observed the Cessna 172 flying approximately 500 feet below him. He described executing a right-hand turn that brought him alongside the Cessna 172 at a distance of roughly 300 meters. He noted that the aircraft gained speed and a climbing attitude during this turn, which resulted in the close pass.
Regarding maintenance, the investigation reviewed the records for both aircraft. The ZS-MEL had undergone its last annual inspection in December 1999, though investigators could not confirm if all airworthiness directives and service bulletins had been addressed. The ZS-LEX had completed a mandatory periodic inspection in early January 2001, with documentation indicating compliance with all necessary directives.
Findings
- The primary cause of the incident was the pilot of the ZS-MEL flying in close proximity to the ZS-LEX while performing a maneuver.
- The Pitts S-1S was in a steep climbing attitude during the pass, which placed it within 10 to 20 meters of the Cessna 172's wing.