What happened
On 4 September 2000, a Bell 407 helicopter, registration ZS-RHK, was performing a commercial operation near the Komatipoort area. The flight was intended to proceed from the Komatipoort area to the Komatipoort Sub Station. During the approach to a landing in a confined area at the substation, the pilot requested that the front-seat passenger assist with monitoring the left side of the aircraft for potential obstacles.
As the aircraft touched down, the pilot reduced the collective pitch. During this maneuver, the main rotor blades made contact with a transformer unit located to the left of the pilot's position. The impact caused extensive damage to the main rotor blades and sent debris striking the tail rotor blade and puncturing the horizontal stabilizer. There were no injuries to the two occupants on board.
The investigation
SACAA AIID investigators examined the wreckage and the site conditions at the Komatipoort Sub Station. The inquiry focused on the sequence of events during the touchdown phase and the spatial relationship between the aircraft's rotor arc and the surrounding infrastructure. The investigation confirmed that the transformer unit was positioned in the seven to eight o'clock position relative to the pilot at the time of the strike.
Findings
- The primary cause of the accident was inadequate clearance between the main rotor blades and the transformer unit on the left side of the helicopter.
- The pilot had actively engaged the passenger to assist with obstacle lookout, indicating awareness of the confined nature of the landing site.
- The impact of the main rotor blades resulted in secondary damage to the tail rotor and the aircraft's vertical fin.