One of only two men to survive a helicopter crash that claimed 45 lives has relived the tragedy 30 years on.

The accident off Shetland on November 6, 1986, remains the worst offshore helicopter disaster in history.

Pilot Pushp Vaid was one of 47 people aboard the Chinook when it plunged into the sea near Sumburgh Airport on a return journey from the Brent oilfield.

He managed to escape the sinking helicopter through the smashed window of the cockpit and was rescued from the water along with passenger Eric Morrans.

Investigators later discovered the helicopter had suffered a catastrophic failure which desynchronised its twin rotors and caused them to collide.

Speaking to STV News, Mr Vaid said the tragedy might have been avoided if not for a last minute change to the Chinook's flight plan.

He recalled: "We took off from Sumburgh Airport and only had two landings to do - Brent Charlie and Brent Delta - but Brent Alpha was added on because some freight had to be dropped off.

"That added ten minutes to our flight and our accident happened only two minutes before landing so we probably would have been on the ground before anything happened."

The first signs of a problem with the helicopter emerged about ten miles south of Sumburgh Airport.

"We had been given clearance to land and came down to 500ft," Mr Vaid said.

"About then we started hearing a whining noise but it didn't sound serious and it wasn't getting louder and we thought we would tell the engineers to have a look before we did our next flight.

"Then there was an almighty bang - the front gearbox had cracked and it was decelerating the front rotor. The rotors began intermeshing and hit each other."

Mr Vaid continued: "The rear rotor parted company from the helicopter and the helicopter tilted over with the nose pointing towards the sky.

"We went from doing 100mph to zero and there was a huge whiplash - I believe about half of the people must have died at that stage. My co-pilot broke his neck."

Mr Vaid believes he only escaped serious injury because he had been sitting back in his seat when the rotors separated from the helicopter.

"I grabbed the stick and hoped the helicopter would come up but it flipped the cockpit over," he said.

"We were now going backwards into the sea. The helicopter hit the water and the entire impact was taken by the cabin. Every seat was smashed.

"When it hit the water the floor broke and the cockpit went into the water. I swam through the window and up to the top.

Mr Vaid added: "I saw wreckage and fuel floating around me, it never occurred to me even for a minute that anybody would be dead. But then a body popped up next to me, and then another, and another.

"I climbed into the wreckage of a fuel tank to get out of the water. I got pushed back into the sea by a wave so I grabbed hold of the tank and stayed there as I knew the rescue helicopter would be there any minute.

"They picked me up and then they saw Eric Morrans and picked him up as well."

With the survivors out of the water, the rescuers turned their attention to getting them medical help.

Mr Vaid said: "My suit was full of cold water because I'd unzipped it in the cockpit, where it gets very hot.

"They cut my socks off and got rid of the water but our body temperatures were still dropping. My eyes were closing and so were Eric's. They decided to take us to hospital before they lost us as well.

"They rushed us to Lerwick and wrapped us up in blankets so our bodies could warm themselves up. The whole left side of my face had been cut by glass and my nose was broken.

"My toes had been broken, too. It was only in hospital where I found out there was nobody else. I couldn't believe it."

Mr Vaid added: "I used to feel like maybe I could have done something - but of course there was nothing I could have done. I used to go to church, to temple, looking for answers. But God decided it was not my turn."

The Chinook was retired from offshore service in the aftermath of the disaster and they no longer carry civilian passengers in the UK.

Mr Vaid believes that was the wrong decision.

"There was nothing wrong with the Chinook," he said.

"They rectified the fault and it should have been back in the air. It was the ideal aircraft, it never bothered us."

An annual service to remember those who have lost their lives in the oil and gas industry will be held at St Nicholas Kirk in Aberdeen on 11am on Saturday.

Reverend Gordon Craig, chaplain to the oil industry, said: "It is really important for families to realise their loved ones are still being remembered and respected by the industry.

"The service is an opportunity to commemorate all those no longer with us.

"Thirty years on from the Chinook crash may seem like a long time but the memories are still vivid for those who lost their loved ones suddenly and tragically.

"The pain may be more manageable but there will still be times when the loss is felt deeply."