Incident Overview
On 2 September 2014, at 10:18 UTC, a near-miss occurred between two aircraft under radar control in the vicinity of Port Elizabeth aerodrome (FAPE) in South Africa. The incident involved a Hawker Beechcraft 390 (registration ZS-ETN) and a Robinson R22 Beta helicopter (registration ZS-RTZ). No injuries or damage to either aircraft were reported.
Operational Context
The Hawker Beechcraft 390 was en route from Bloemfontein aerodrome (FABL) to Port Elizabeth on an Instrument Flight Rules (IFR) flight plan. The Robinson R22 was conducting instrument flying training at FAPE, also under IFR. At the time of the incident, a student air traffic controller, supervised by an instructor, was managing approach control.
Sequence of Events
During descent to 4,000 feet, the pilot of ZS-ETN received a Traffic Alert and Collision Avoidance System (TCAS) warning on the primary flight display. The pilot immediately initiated evasive action by turning right. Radar analysis later confirmed that ZS-ETN was on a head-on collision path with ZS-RTZ. At the moment of the TCAS alert, horizontal separation was approximately one nautical mile and vertical separation was 100 feet.
The helicopter crew had previously read back an incorrect altitude instruction (4,000 feet instead of the instructed 3,000 feet). Neither the student controller nor the instructor detected this error. A Clear Level Alert Monitoring (CLAM) amber warning remained active on the controllers' screens for four minutes without intervention. The Short-Term Conflict Alert (STCA) system did not trigger because the helicopter's speed was below the system's minimum detection threshold.
Probable Cause
The investigation determined that the incident resulted from a lapse in concentration by the student controller, who failed to take corrective action after the pilot of ZS-RTZ read back an incorrect altitude. This failure led to a loss of separation between the two aircraft in both horizontal and vertical planes.