Preliminary report on Killucan helicopter crash report issued by air accident investigators

The Air Accident Investigation Unit (AAIU) has produced a preliminary report on the helicopter crash that occurred at Killucan on July 30 that claimed two lives.

The report suggests that it is likely that the helicopter was engaged in an exercise known as autorotations when the accident occurred.

The report does not set out a final determination regarding the circumstances of the crash of the Bell Textron Jet Ranger X 505 helicopter nor outline probable causes: the AAIU explains that the safety investigation is exclusively of a technical nature and these issues will be addressed in the final report.

The AAIU also stresses 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.”

The Canadian-built US-registered helicopter was just four years old and was on a flight training operation when the accident happened. The two who died were an instructor and a student pilot. The instructor had come to Ireland just two days earlier to train the man who died and three other students on the Bell Jet Ranger 505.

The student pilot had commenced helicopter flight training on July 1 2022 at Weston Aerodrome (EIWT), and completed it on June 17, and following completion on June 25 2024 of a skills test, he was on July 25 awarded a Private Pilot Licence for certain helicopters.

At the time of the accident, the student had completed approximately 105 hours of flying time, two hours and 53 minutes of which were in the subject helicopter.

The instructor had completed 5,253 hours 14 minutes, of which the total on this type of helicopter was 325 hours 56 minutes. His examiner certificate was issued by the Civil Aviation Authority of the Czech Republic and was valid until March 31 2025.

The report stated that the helicopter in which they were traveling was is capable of carrying up to four passengers plus a pilot and was fitted with dual controls.

The investigation report stated that during his training period, the student pilot acquired the subject helicopter, and on Monday July 29 he and three other pilots were scheduled to begin training on that type of helicopter.

To provide the training, a qualified flight instructor arrived in Ireland on Sunday, July 28 2024. The following morning, one of the other pilots collected the instructor from his hotel and brought him to Weston.

That morning, the instructor underwent an induction course with a senior pilot and following the induction course, the instructor met with the four trainees.

During Monday, July 29, one of the trainees flew with the instructor on two training flights followed by the student, who also completed two training flights.

The following morning, the day of the accident, the student and the instructor completed a 44-minute flight in the helicopter, departing at 08.49 hrs and returning at 09:33 hrs. Following this flight, the instructor completed a training flight with one of the other trainees. Subsequently, that trainee said that he witnessed the instructor briefing the student on an exercise that includes ‘autorotations’, which are manoeuvres that simulate an engine failure in flight in which the engine is disengaged from the main rotor disc and the rotor blades are driven solely by the upward flow of air through the rotor.

Discussing what was to be the helicopter's final flight, the investigators state that it departed Weston Airport at 13.58 hrs, proceeding generally westwards, and five manoeuvres, which appear to have been practice autorotations, were carried out. At approximately 14:25 hrs, in the vicinity of Killucan, during what appears to have been a sixth practice autorotation, the helicopter impacted with the surface of an agricultural field.

“It then travelled 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.”

5. AUTOROTATION

The investigation report states that flight training for all aircraft includes training pilots to respond appropriately to an engine failure in flight; in the case of single-engine helicopters, the technique that is taught is called an ‘autorotation’.

It explains that the rate of descent in an autorotation is controlled with airspeed and rotor rpm, adding that rotor rpm is a critically important parameter for all helicopter operations and that below a certain rotor rpm, helicopters will not fly and will stall.

Location

The Investigation conducted a detailed survey of the accident site and the wreckage was recovered to the AAIU’s wreckage facility at Gormanston, Co, Meath, for examination.

At the accident site, it was noted that the tail section of the helicopter was still loosely attached but fractured and bent away from the airframe. The rotor head and main rotor blades remained attached but were badly damaged. There was no evidence of a fuel leak. The investigation did not find any evidence that the main rotor blades had impacted the ground or the structure of the helicopter.

A representative of the French national Safety Investigation Authority the Bureau d'enquêtes et d'analyses pour la sécurité de l'aviation civile (BEA), an advisor from the France-based engine manufacturer, and an advisor from the Canada-based helicopter manufacturer, attended the AAIU’s wreckage examination facility, to assist the Investigation.

At the request of the AAIU, the BEA representative has taken the helicopter’s engine control unit to France where the data will be downloaded from it.

The report stated that the investigators spoke with many witnesses although none had actually observed the final moments of the helicopter’s flight: “Witnesses variously described seeing the helicopter descending rapidly as if to land before climbing away again; several described hearing the helicopter’s engine going quiet and then becoming loud again,” the investigators wrote, adding that the descending and climbing manoeuvres were consistent with autorotation training, while the variation in engine sound was consistent with the helicopter operation alternating between the ‘Idle’ and ‘Fly’ modes when initiating and completing autorotations.

The report concluded by stating that the investigation is ongoing, and that a final report will be published in due course.