The crash - which is being investigated by the Civil Aviation Authority - killed fellow glider pilot Ichiro Murai (54), of Japan, and left Mr Tanner with serious injuries.
Speaking to the Otago Daily Times from Dunedin Hospital yesterday, the 68-year-old Englishman said his last recollection in the moments leading up to the crash was of warning Mr Murai the glider was too close to the slopes of Mount St Cuthbert.
The Duo Discus two-seater glider was being piloted by Mr Murai, seated in front of Mr Tanner, when the accident occurred about 2pm, Mr Tanner said.
"I just remember saying we were too close in to the hillside, and then I don't remember anything until waking up in the wreckage," he said.
The glider had just launched from the nearby Omarama airfield, and was undertaking a normal thermalling manoeuvre to gain height - which involved circling near the hillside to take advantage of air currents - when the accident happened.
Mr Murai - with about 1000 hours' flying experience to his name - was in Omarama for a series of gliding flights with Omarama-based instructors, including Mr Tanner, and had undertaken other flights earlier in the week without incident, Mr Tanner said.
Mr Tanner only met Mr Murai that week, and "hadn't really had much to do with him" prior to Friday's fatal flight.
Mr Tanner said he could not confirm an account by GlideOmarama owner Gavin Wills, published in a community newsletter, that the glider's wing had struck a partially obscured rock.
"I can't say that because I don't remember hitting the ground," he said.
Mr Wills yesterday told the ODT the crash may have also been the result of a "miscommunication" between the pair, leading to Mr Murai trying a last - fatal - turn when too close, having mistakenly thought that was Mr Tanner's instruction.
The complete story might never be known unless Mr Tanner's recollection of the crash returned, Mr Wills said.
Mr Tanner received two broken ribs, a punctured lung and fractures of a lumbar vertebrae, his pelvis, sternum and right heel bone.
He was flown to Omarama and then on to Dunedin Hospital, underwent an operation, and remained in the hospital's intensive care unit until being transferred to a ward on Monday.
He faces about three weeks of rehabilitation before he can expect to be released.
A large group of friends had gathered to support Mr Tanner - a former RAF fighter-bomber pilot and commercial helicopter pilot with worldwide experience.
He plans to return to the UK a few weeks after his release from hospital and has no plans to give up gliding.
