Joan Peasgood said relatives feared her brother John Russell was dead after he went missing during a cross-country gliding contest but added that the experience has not put him off the sport he loves.
Mr Russell, 64, of Sutton-on-the-Forest, near York, is recovering in Aberdeen Royal Infirmary after his ordeal, which began on Monday as he set out on a competitive glider flight from Aboyne in Aberdeenshire.
Worried staff at Deeside Gliding Club, which was hosting the contest, raised the alarm after Mr Russell – an experienced glider and member of Yorkshire Gliding Club, based at Sutton Bank, near Thirsk – had failed to return some 11 hours later.
Mrs Peasgood, of Mill Lane West, Elloughton, near Hull, has spoken to her brother, who described what he had been through as a "life-changing experience".
"It is a miracle," she said. "I have spoken to him. I said 'Does that mean you won't be gliding again?' and he said: 'Not at all'.
"We all thought he was dead because he was there nearly 30 hours. It was a miracle he was found.
"We were told he just had a broken ankle and fractures. But he has a severe fracture of the left leg and is having an operation tomorrow.
"It was bitterly cold. He was trapped in his glider for 28 hours and I think he got some frostbite in his toes.
"Obviously he is in a lot of pain but he is in good spirits because he realises how lucky he is to be alive."
Mrs Peasgood said her brother, a father of three grown-up children and grandfather of one, would be coping with what had happened but loved ones were concerned about his undergoing surgery.
Mr Russell divorced a long time ago and is engaged to be married again. His fiancée is understood to have travelled to Scotland and is at his bedside in hospital.
"He is a very positive person," said Mrs Peasgood. "He climbs, walks, and does birdwatching. He is a very experienced glider pilot which has taken up a lot of his life since he retired."
Mr Russell, who was born in Brough, went to Goole Grammar School and later Nottingham University, where he studied for a PhD.
He worked for ICI all his life, mainly at Billingham, in Teesside, and for the last four years of his career was president of ICI in Japan. He was awarded the CBE a number of years ago.
Mrs Peasgood said her brother had recounted the dramatic moments before his glider crashed.
"He was high up in the Grampians," she said.
"Cloud came pouring in and he could not see. He lost radio contact. He was looking for the gliding club then he saw the ground rushing up to and realised he was crashing."
Mr Russell told her one wing of the glider had dug itself into the ground and the aircraft tilted over and went into the ground.
The glider canopy came off and her brother was trapped in the cockpit, which was reasonably intact, but he could not move because of his leg injury.
After RAF air crews spotted the wreckage and Mr Russell waving inside, rescue teams were directed to the crash scene and he was cut free.
From there, Mrs Peasgood said her brother was taken to Aberdeen Royal Infirmary, where he remains in intensive care and was being given morphine.
"His family had known all day he was missing and thought he was dead. It was a terrible shock," Mrs Peasgood said.
"But then we got a message through that a plane had seen the wreckage of a glider and a man in it waving so we thought: 'At least he is alive'."
Yorkshire Gliding Club chairman Graham Evison thanked all those who had taken part in the "extensive" search to find Mr Russell, who is an instructor at the club.
"And we look forward to John's returning to Yorkshire," he said.