Cause of chopper crash that killed Irish tech tycoon and instructor revealed

Both men were killed at a farm near the village of Killucan on July 30, 2024, while Czech pilot Antonin Kabelka was giving flight training to the tech millionaire in a dual-control Bell helicopter.

A report released on Friday by the Air Accident Investigation Unit (AAIU) reached the same conclusion as an earlier, preliminary investigation weeks after the crash – that it had been caused by a problem during an autorotation maneuver.

Autorotation is a state of flight in which a helicopter’s main rotor spins solely from the aerodynamic force of air moving up through the rotors, rather than engine power, allowing the aircraft to safely descend and land if the engine fails.

Practicing autorotation is common for pilots as it teaches them how to react if a genuine engine problem occurs.

The crash happened during Mr Crosby and Mr Kabelka’s sixth practice autorotation, almost 30 minutes into the flight from Weston Airport, and was not a survivable crash, the AAIU found.

Mr Crosby, aged 46, was a father of two and Mr Kabelka, 48, had three children.

The five-seater helicopter hit a field, then traveled forwards and collided with the gable wall and roof of an agricultural building.

Data from the aircraft showed that it had tilted to the left before the crash due to an increase in power from the tail rotor.

The helicopter then began to enter a "sideslip" where it moved sideways through the air without turning as it dropped altitude significantly.

One of the crew members may have pulled a lever by accident when they were momentarily lifted from their seat by the sudden fall in altitude, the report continued, which made the helicopter’s maneuvering even more unstable, and the aircraft later turned nearly completely on its side just before the crash.

The AAIU noted: "The number one error in practice autorotations is the failure of the flight instructor to take control of the aircraft and terminate the maneuver before it progresses to a point where the flight instructor is not capable of recovering the aircraft in time to prevent damage to the aircraft or injury to personnel."

The investigation determined that, while Mr Kabelka took over control of the helicopter before the crash, there wasn’t enough time for him to prevent it. The report also pointed out the safety risks of autorotation and said practicing them for a prolonged period can increase the risk of human error at the controls.

"Statistics for helicopter accidents indicate the greatest exposure for an accident or incident occurs during practice autorotations.

"A high percentage of training accidents occur after many consecutive autorotations. To maintain instructor focus and minimize student fatigue, limit practice to no more than three or four consecutive autorotations.

"Accordingly, it is possible that completing six consecutive autorotations adversely affected the instructor’s focus, and/or caused the student to become fatigued, which may have contributed to the accident sequence."

The AAIU also stressed that safety investigations are in no case concerned with apportioning blame or liability.

"They are independent of, separate from and without prejudice to any judicial or administrative proceedings to apportion blame or liability. The sole objective of this safety investigation is the prevention of accidents and incidents."

Mr Crosby had over 100 hours of flight experience, just under three hours of which were in the helicopter from the crash in the days before and on the morning of his death.

The report found that although Mr Kabelka had a commercial pilot’s license issued by the Czech Republic, he was technically required to have obtained one from either Ireland, where the training took place, or the United States, where the helicopter was registered.

Postmortems of both men concluded that their deaths were due to asphyxia and chest compression injuries sustained in the accident and both had fractured ribs.

The instructor had come to Ireland just two days earlier to train Mr Crosby and three other students on the aircraft.

Describing what was to be the helicopter’s final flight, the investigators state that it departed Weston Airport at 1.58pm and got into difficulty at approximately 2.25pm.

"It then traveled forwards at a height sufficient to clear a boundary fence and impacted with a gable wall of an agricultural building.

"The helicopter came to rest, in a nose-down orientation, in the wall and the roof of the building. Both occupants were fatally injured," the report said.

Three contributory factors in the crash were identified: "The unusual attitude entered during the final phase of the maneuver, insufficient height to regain control of the helicopter and effect a recovery, and possible adverse effects of completing a series of six consecutive autorotation maneuvers."

Mr Crosby, from south Dublin, was the founder of AG Grid, a software firm used by 90% of Fortune 500 companies. He left an estate worth € 16.5 million.

* This article was originally published on Extra.ie.