A report by the Air Accident Investigation Unit said the probable cause of the accident was a controlled flight by the Cessna T182T into the Blackstairs Mountain on the morning of May 24, 2015.
The pilot and a passenger, along with two dogs, were all killed.
A controlled flight into terrain indicates a pilot is generally unaware of the danger until it is too late. Since 1968, there have been 12 other flights in Ireland involving impact with elevated ground resulting in 35 deaths. All occurred in poor weather conditions.
Data from a portable device found on the aircraft showed the flight was at 2,000ft and in a shallow climb just before the accident and on track to fly just south of the mountain’s 2,400ft summit.
The pilot, Paul Smith, aged 57, of Rathmore, Athboy, Co Meath, and his passenger, Bryan Keane, aged 69, of Williamstown, Kells, Co Meath, were en route to a breakfast “fly-in” organised by the Irish Light Aviation Society at an airfield near Taghmon, Co Wexford, at the time of the accident.
They had departed earlier that day from an airfield in Athboy.
Both men were described as having been in good spirits and looking forward to their trip.
The aircraft crashed around 9.30am on a steep, rocky, slope on the western side of a ridge near the mountain’s summit.
A hillwalker came across the wreckage at around 1.40pm and alerted the emergency services.
The AAIU report noted no flight plan had been filed so that air traffic controllers were unaware the flight had been overdue at its destination.
Both men were killed instantly. However, the AAIU advised that fliers’ survival chances were improved by ensuring the details of a planned flight were notified to third parties.
While a pathology report prepared for the inquest into the deaths suggested the pilot might have suffered a heart attack during the flight, given he had a known history of heart disease, the AAIU said further advice received from medical experts meant it was impossible to conclude if it played any contributory factor in the accident.
However, they noted the passenger, who also had a pilot’s licence, would have been capable of taking control of the aircraft if Mr Smith had suffered some incapacity but there was no evidence that had happened.
AAIU inspectors said the Cessna aircraft was well maintained and did not have any pre-accident defects.
Poor visibility and cloudy conditions above 1,000ft at the time of the accident were reported by Met Éireann, while locals also described how the mountain had been covered by low cloud and rain.
The AAIU report said that the safest and simplest course of action to have taken, given the prevailing weather at the time, would have been to deviate around the mountain.