What happened
On 15 June 2009, a Cessna Caravan 208B, registration ZS-OXV, was conducting a non-scheduled domestic charter flight from Makuleke to Wonderboom Aerodrome. While flying under IFR flight rules, the crew transitioned to VFR as they approached the Pretoria General Flying Area. As the aircraft was crossing the N1 highway on its final approach for Runway 29, the crew identified another aircraft approaching from the right at a similar altitude.
The second aircraft, a Piper Cherokee Arrow, registration ZS-LSG, was positioned on a late downwind leg for the same runway. To prevent a collision, the pilot of ZS-OXV performed an immediate leftward descent. Both aircraft managed to land safely without any injuries or damage to the airframes.
The investigation
An investigation by the SACAA AIID focused on the sequence of events leading to the near-miss. The inquiry examined the communication between the Air Traffic Control (ATC) tower and the aircraft in the circuit. It was established that the tower's VHF radio was experiencing intermittent and weak transmissions, which caused significant confusion.
Specifically, the controller had attempted to instruct ZS-LSG to perform a left-hand orbit and to descend to a specific altitude, but these instructions were not heard or understood by the pilot due to the radio's poor performance. Consequently, the pilot of ZS-LSG proceeded to turn base without the intended separation, placing them on a collision course with the approaching Caravan.