[1] Towards the end of November 1962 he travelled to Marseille, France, with Lieutenant John Kelly, to collect a pair of Aérospatiale Alouette III helicopters (tail numbers A195 and A196).

[1][2] Whilst still training on the new aircraft at Baldonnel Aerodrome, McMahon was, on 23 December 1962, called out to a search and rescue mission off the Connemara coast.

Knowing it would take six hours for aviation fuel to be sent there from Baldonnel, McMahon sought out a local garage and purchased 120 imperial gallons (550 L; 140 US gal) of petrol for his aircraft.

He mixed this with a quantity of paraffin procured from the town's priest and filtered the mixture through a pair of tights, possibly supplied by the garage owner's wife.

[1][3] The handball alley afterwards became an unofficial landing spot for the Air Sea Rescue Unit and later became a fuel depot for the company Irish Helicopters.

He was commended for exhibiting "a high degree of courage, exceptional flying skills and a disregard for personal safety" during the operation in which he flew his helicopter within 2 feet (0.61 m) of the cliff face.

[1] McMahon was responsible for introducing an air ambulance service to Ireland, the first in Europe, for transporting patients with spinal injuries to the National Rehabilitation Hospital in Dublin.

[1] He returned to Baldonnel (by then named Casement Aerodrome) on 21 September 2007 for a ceremony to mark the retirement of the Alouette III from Irish Defence Force service.