Close Proximity Between Two Cessna 172P Aircraft at Wonderboom National Aerodrome (ZS-GDA and ZS-PMX)

Incident Overview On 10 May 2021, a serious incident occurred involving two Cessna 172P aircraft, ZS-GDA and ZS-PMX, during flight training operations in the general flying area of FAD 127 near Wonderboom National Aerodrome (FAWB). Both aircraft were conducting training exercises, and the incident resulted in no injuries or fatalities. ## Aircraft and Personnel The first aircraft, ZS-GDA, had a total of 18,141.1 flight hours and was operated by a commercial pilot with 1,010.0 total flying hours and 980.0 hours on type. The second aircraft, ZS-PMX, had 6,362.5 total flight hours and was operated by an airline transport pilot with 13,350.3 total flying hours and 1,664.2 hours on type. Each aircraft carried one instructor and one student pilot. ## Sequence of Events ZS-GDA departed FAWB at 1333Z and proceeded to FAD 127 to conduct stalling exercises at 7,000 feet. ZS-PMX departed at 1353Z for the same area. Radar data indicated that ZS-PMX entered FAD 127 at 13:59:29Z and made several turns. At 14:08:18Z, the two aircraft came too close to each other. ZS-GDA was flying at 6,900 feet in a southerly direction, while ZS-PMX was heading north-northeast. The transponder mode C on ZS-PMX was not detected, preventing radar from determining its altitude. ## Probable Cause The investigation found no evidence of avoidance maneuvers. It is likely that ZS-PMX did not correctly change the radio frequency upon entering the general flying area, resulting in the crew not being heard by other aircraft. The two aircraft may have flown very close to each other due to this communication issue. ## Safety Recommendations The report recommended that all aircraft flying in South Africa file a flight plan to facilitate radar tracking and squawk code allocation. Pilots were advised to remain vigilant in congested areas, maintain proper lookout, and ensure radios are in good working condition. Hand-held radios were recommended as a backup.