What happened
On June 29, 2012, at approximately 08:58 local time, a Hughes Helicopters, Inc. HU 369D was performing vineyard spraying operations near Lieser, Germany. During the eighth flight of the day, the helicopter collided with a 110-kV high-voltage power line.
Witnesses observed the aircraft flying from the southeast toward the northwest before executing a turn back toward the power lines. During the collision, the helicopter struck four of the six power cables, severing them, while the earth wire remained intact. The impact caused the destruction of the aircraft and the fatal injury of the pilot. The collision also caused significant damage to the power lines, leading to widespread electricity outages in several local communities for several hours.
The investigation
The BFU investigation examined the aircraft, the pilot's credentials, and the operator's safety procedures. The pilot was a highly experienced professional with approximately 4,224 total flight hours, including over 1,000 hours on the HU 369D.
Investigators recovered a spraying plan from the crash site, which featured the power line highlighted in pen. The investigation also reviewed the operator's safety management. While the operator had held discussions with the pilot following a similar wire-strike incident involving the same aircraft one year prior, no formal, documented procedures had been developed to specifically prevent power line incursions. Furthermore, the operator's flight operations manual, which was awaiting approval, lacked specific procedures for vineyard spraying operations.
Findings
- The primary cause of the accident was the collision with the 110-kV power line.
- The aircraft was not equipped with "cable-cutter" technology, although such equipment was available for this model.
- A previous incident involving the same aircraft occurred on June 16, 2011, when the rotor blades struck a 20-kV line, though the pilot landed safely.
- The operator had not implemented specific, documented procedures or training to mitigate the risks associated with low-level spraying near power lines, relying instead on informal verbal warnings.