Witnesses have told the opening day of an inquiry into the Clutha helicopter crash in Glasgow five years ago they heard a spluttering and grinding noise before it fell from the sky.

Andrew Bergin, a solicitor from Airdrie, North Lanarkshire, told the fatal accident inquiry (FAI) he saw the helicopter’s rotor lose power and its light die before it crashed seconds later, killing 10 people on Friday 29 November 2013.

The helicopter slammed into the roof of the Clutha Vaults bar, killing its pilot, two police officers and seven customers. They were among about 100 people packed into the popular pub on the banks of the Clyde.

“It made what I can only describe as a spluttering noise. It wasn’t any lower than I would have seen it before,” Bergin told the inquiry. “The tail of the helicopter dipped and pointed to the ground. Simultaneously, the light on the helicopter went out.

“It seemed to me that the rotor stopped spinning. It was still turning, but not under power. It seemed to immediately lose height as soon as the spluttering occurred. Everything happened more or less at the same time.”

The inquiry, before Sheriff Principal Craig Turnbull, is being staged in a temporary court at Hampden Park football stadium to accommodate scores of witnesses, aviation experts and family members.

Roughly equivalent to an inquest, the FAI has to establish what caused the fatal crash and how the victims died, and is due to hear about 17 weeks of oral evidence spread out over five months. Breaks in the hearings are being scheduled to fit around football matches and concerts.

The inquiry will not apportion blame but the original inquiry by the Air Accidents Investigation Branch (AAIB) found that two fuel supply switches were turned off and the pilot, David Traill, 51, did not follow emergency procedures after a fuel warning sounded in the cockpit.

The helicopter, leased by Police Scotland from Bond Air Services, was flying back to its base west of the Clutha when the crash happened. Witnesses at the time suggested Traill tried to land the helicopter on the bar’s roof to avoid casualties, but the roof caved in under the force of its landing.

A second witness, Brian Stewart, an electric production operator, 41, from Glasgow, said he heard the helicopter’s engine cutting out before it plunged downwards. “It was kind of like when you stall your car when you have it in the wrong gear and it struggles, kind of like that,” he said.

“I noticed the flashing light underneath. It seemed to be slowing down as it fell out of the sky. The engine started cutting. It happened a couple of times, then it fell behind the building in front of me on Turnbull Street.”

The Crown Office, Scotland’s prosecution authority, ruled there was not enough evidence to justify criminal proceedings. The police interviewed 2,000 witnesses and amassed 1,400 pieces of evidence for the FAI.

After a minute’s silence, the hearing began with statements from relatives of the deceased. A statement from relatives of Colin Gibson, a 33-year-old customer who had never been to the Clutha before that night, said: “If you were lucky enough to meet him, you knew you had, as he left a lasting impression on you.”

The sisters of Gary Arthur, 48, told the inquiry: “He was caring, loving and could also be annoying in our younger years. He was a joker and he continued to be a loving rogue throughout his life. Nothing will ever bring our brother back, but hopefully we will finally be given the chance to find closure.”

The other victims were the police officers Tony Collins, 43, and Kirsty Nelis, 36, and Clutha customers Samuel McGhee, 56, Robert Jenkins, 61, Colin Gibson, 33, John McGarrigle, 57, Mark O’Prey, 44, and Joe Cusker, 59.

Jenkins worked at the Scottish Football Museum, housed in Hampden Park stadium where the inquiry is taking place. It resumes on Tuesday with evidence from the AAIB.