Search and rescue volunteers were alerted at 1pm yesterday after a woman in her 40s slipped and hit her head whilst crossing the summit plateau between the Pen y Gader and Mynydd Moel peaks.
She was bleeding profusely, and both she and her partner were anxious, cold and wet.
Aberdyfi Search and Rescue team started the hour long walk up the mountain requesting help from Coastguard Helicopter Rescue936.
Team spokesman, Graham O'Hanlon said the helicopter took off to support the rescue, but was unfortunately forced to turn back by poor weather that had shrouded the mountains in cloud.
"Having reached the injured woman on foot, the volunteers put the woman in a casualty bag on a stretcher to try and keep her warm and prepared for the prolonged and very difficult stretcher-carry down to Minffordd," he said.
"As the stretcher party started to descend the main slope of Mynydd Moel, there was a hint of slightly improving weather conditions, and once again helicopter assistance was requested.
"This time the aircraft was able to reach the mountain, but the cloudbase meant that it could not quite reach the stretcher party.
"The crew landed the aircraft nearby, giving rescuers the chance to move a little further down the mountain, before they took off and winched the casualty aboard.
"The injured woman was flown to Ysbwyty Gwynedd for further assessment and treatment. "
He said 32 volunteers were involved in the seven hour rescue operation.
"Without the repeated attempts in difficult conditions by R936 to assist this rescue, the team faced a long and very challenging carry down the mountain in the dark," he added.
"As it was, rescuers had been attending this incident for seven hours, and without the air-lift it would have continued for a fair number more."