PRIVATE FLIGHT: A Piper PA-28-180, the type of plane involved in an incident over Forbes in January 2014.

The passenger of a light aircraft was forced to take control of the plane when the pilot passed out 10 minutes after take off, the Australian Transport Safety Bureau has found.

The Piper plane had just taken off from Forbes airport in central western NSW on January 25 when the pilot suffered a seizure and lost consciousness.

The sole passenger on the private flight, who had never landed a plane before, took the controls and turned the plane back towards the airport. He also used the plane's radio to call for help, rousing a nearby pilot who helped talk him through what to do.

After circling the airport for 22 minutes, the original pilot regained consciousness and was able to execute a rough landing.

The terrifying circumstances were outlined in the Australian Transport Safety Bureau's (ATSB) report, released on Thursday.

The report said that a doctor later determined that the pilot had probably lost consciousness due to dehydration.

The pilot told the bureau that he had stayed up late the night before the flight and had consumed a "moderate amount of alcohol", before sleeping for about five or six hours.

He was feeling unwell on the morning of the flight but still decided to fly on what turned out to be a hot day, with temperatures between 36 and 38 degrees, the report said.

On the morning of the flight, the pilot consumed only a cup of coffee but no other liquids or food.

The pilot told the ATSB that he did not recall any of the flight after the initial climb, until when the aircraft was lined up for a landing at the airport.

The report said when the pilot was unconscious, the passenger managed to steer the plane for 22 minutes with the help of another pilot, who had just taken off from Forbes airport and heard his broadcast for help.

The passenger who had taken controls of the plane told the second pilot over the radio that he had never landed a plane before.

Members of a local gliding club called emergency services, while a rescue helicopter and another aircraft were both diverted to the area to help.

The ATSB said that the pilot regained consciousness and landed just short of the runway's threshhold, bounced once and veered off the runway during the landing roll.

The pilot was assessed by paramedics and flown to Orange Base Hospital.

"This incident highlights the importance of pilots assessing their fitness to fly prior to every flight," the ATSB said.

Civil Aviation Regulations cite that pilots must wait a minimum of eight hours after drinking alcohol before commencing a flight.

"However, a more conservative approach is to wait 24 hours from the last use of alcohol before flying," Federal Aviation Administration guidelines say.