What happened
On May 4, 2019, a Robinson R44 helicopter, registration HK4449, was performing a non-scheduled passenger flight near Guatapé, Antioquia, Colombia. The aircraft, operated by Aeroexpress S.A.S., was preparing for a local flight from the Helitours helipad with one pilot and three passengers on board.
During the takeoff roll, after traveling approximately 23 meters at a speed of 10 knots, the pilot experienced a sudden, heavy descent. In an attempt to abort the takeoff, the pilot executed a pronounced flare maneuver. This action caused the main rotor blades to strike the aircraft's tail cone, resulting in the separation of the cone from the structure. The helicopter immediately descended to the ground. There were no injuries among the four occupants, and no post-impact fire occurred.
The investigation
The GRIAA investigation focused on the mechanical failure and the maintenance history of the engine components. Investigators examined the engine's magneto system and discovered that the right magneto was inoperable due to an electrical ground fault.
Technical analysis revealed that a maintenance facility (TAR) had performed an unauthorized repair on the magneto's "P-lead" wire. This repair was substandard, leaving loose internal wire strands that eventually made contact with other components, creating a direct path to ground. Furthermore, the investigation noted that the pilot had not performed a magneto check prior to the takeoff attempt. While the aircraft was operating within its weight and balance limits, the performance was noted to be near the restrictive limits for out-of-ground-effect (OGE) operations.
Findings
- The primary cause of the structural damage was the impact of the main rotor blades against the tail cone during the aborted takeoff maneuver.
- The loss of power during takeoff was caused by the inoperability of the right magneto due to an electrical ground fault.
- The failure originated from inadequate maintenance practices by the repair shop, specifically an unauthorized and improper repair of the magneto P-lead.
- The pilot did not conduct a magneto check before initiating the takeoff.