History of Flight
On 21 January 2021, a Bell 430 helicopter (registration ZT-RRT) departed Ultimate Heli heliport in Midrand, Gauteng Province, at 0948Z on a commercial medical flight (Part 138) to collect a patient from Hillcrest Hospital in Pietermaritzburg, KwaZulu-Natal. The helicopter carried five occupants: a pilot, a helicopter paramedic, two medical doctors, and a theatre nurse. According to Spidertracks data, the helicopter cruised at an average height of 725 feet above ground level (AGL) at a speed of 135 mph in a south-easterly direction along the N3 Highway. Fuel endurance was 2 hours 30 minutes, and weight and balance were within limits.
Accident Sequence
The last Spidertracks data (position 361) recorded the helicopter at 725 ft AGL and 132 mph. Shortly after, eyewitnesses on the N3 Highway near the Winterton off ramp and on a nearby farm observed white smoke coming from the top of the helicopter, followed by the helicopter spinning and losing altitude. The helicopter then flew over the main road, impacted the ground, and was destroyed by post-impact fire. All five occupants were fatally injured.
Wreckage and Impact
The wreckage distribution spanned 500 meters, including across the main road. Before impact, several major components separated in-flight: the tail boom, windshield, and tail rotor fell at different locations. The main rotor blades broke off from the main rotor mast and were found at various positions away from the main wreckage.
Probable Cause
Post-accident examination revealed a fatigue crack on the threaded part of the clevis of the pitch control lever of the Orange blade, which failed in-flight. This failure caused instability in the main rotor disc, which subsequently severed the rear section of the tail boom. The main rotor blades then failed. The combination of the severed tail boom and main rotor failure led to the pilot losing control, resulting in the crash. The investigation identified corrosion fatigue/metal fatigue, mechanical failure, and improper maintenance as the cause. Contributing factors included failure to identify the fatigue crack during magnetic particle inspection and mandatory periodic inspection (MPI).