The investigation into the June 2016 air crash in the Alentejo, in which the pilot of a Pilatus PC-6 died and two of the seven on board were seriously injured, has concluded that the aircraft has wear and cracking in a critical component, which failed.
The final report from the Aircraft Accident Prevention and Investigation Office (GPIAAF), indicates that a horizontal stabiliser became loose and started to vibration uncontrollably, causing its left side to fracture.
This was the highly likely cause of the accident.
The companmy, Pilatus, noted in a service report issued after the accident that wear and cracks had been found in the ‘stabiliser compensator and relevant structural components’ on some of its aircraft, including in the PC-6.
The GPIAAF report reads that this particular component, "showed that both fractured surfaces had significant cracks due to fatigue, and that these fatigue cracks began at several points, which means that there was no single origin of the crack." The investigators recommend that this component is replaced more often and inspected more regularly.
The aircraft experienced a catastrophic malfunction in mid-flight on June 19, 2016, after taking off from the Figueira dos Cavaleiros aerodrome in Canhestros, in Beja. The German-registered Pilatus PC-6 aircraft was operated by the Seven Air Group which owns the Aerovip air service and the skydiving company Skyfall.
The PC-6 took off from the Figueira dos Cavaleiros aerodrome, with five parachutists and two tandem skydivers. The aircraft disintegrated in mid-flight.
Three of the parachutists were unconscious when they fell from the fuselage at around 7,000 feet but were saved by their parachutes which automatically opened due to a fail-safe barometric trigger. The other four passengers managed to jump from the aeroplane and open their parachutes manually.
The pilot, Jérôme Louis, plummeted to the ground in what remained of the cockpit of the aircraft and crashed about 400 metres from the main fuselage crash site.
The accident report stated that, according to some of the group's parachutists, "a sound similar to that of the metal structure breaking," was heard and that "suddenly the whole rear of the structure disintegrated."
"Some occupants were projected against the structure of the aircraft before being thrown out. In the next few seconds, the parachutists who had not suffered serious injuries were able to jump off the plane and open their parachutes. Two suffered serious injuries before leaving the aircraft and the emergency parachute with barometric opening was activated.”
The accident killed the 27-year-old Belgian driver, seriously injured two paratroopers, one of the occupants was slightly injured and four were unharmed.
"Due to the disintegration of the aircraft in flight and the place where the pilot's body landed, it is assumed that the pilot attempted to leave the aircraft cabin after all the parachutists had jumped, but due to the instability of the flight he may have been knocked unconscious, failing to open his parachute," reports the GPIAAF.
The document indicates that the pilot had flown more than 900 flight hours on the Pilatus PC-6 and had a total flight time of over 1,400 hours. The pilot’s seating area was fitted with safety belts and he also was equipped with a manual parachute.
"The pilot's parachute did not open because it was not equipped with the safety opening system that other occupants' parachutes had," explains the final report of the investigation.
It is not the role of the GPIAAF to apportion blame, that is for the public prosecutor to do and to raise criminal charges if crimes or offences have been committed.
