The Flying Doctors (1986) : 5x13

DJ gets a call, a stationhand has a broken leg. Chris flies out and sees the worker - who turns out to be Tom Callaghan!! He isn't too badly hurt and everybody wonders why Tom isn't working as a doctor. They throw him a big welcome-back-party at the pub, but he acts strangely and is very rude. The following the his flies out to the property where he is working with David. But in the plane David is stung by wasps and has an allergic reaction. Tom performs a tracheotomy and calls Mayday. Sam is out on a clinicround and can't help, so Chris takes a Cessna up and tries to talk Tom down. Amazingly he manages to land the plane with only a few difficulties. Later Tom talks to Chris about some things he experienced in Africa, but then leaves for the farm.