Mr Mitchell (48) beached his aircraft on Friday afternoon.
He was on a round trip from Mosgiel to Karitane with stepson Paddy Smythe (9) when the plane's engine began to ''cough'' on the return leg. The engine sparked back to life but then the misfire worsened, he said.
He radioed Dunedin's air traffic control of the partial engine failure and the impending emergency landing.
The plane was about 550m above sea level and losing altitude fast when he decided a paddock near Larnach Castle was his best option.
''I was lining up the paddock but we were too high and too fast.''
He aborted the landing and, as the engine failed completely, he turned the plane towards Otago Peninsula's south coast with a beach and hard sand in mind.
''By this stage, we were sinking pretty quick ... We managed to sneak around the wee cliff on the northern end and there was Tomahawk Beach - fantastic - but the four people straight in front of us was a problem.''
With no engine noise, the people walking south on hard sand were unaware of the plane ''sinking like a stone'' and speeding towards them.
In desperation, he flashed the landing light on the front of plane, hoping the walkers would notice.
But as he flew closer, he realised the people were walking away from him and he needed a new plan, quickly.
''I threw the plane into the soft sand, otherwise I would have killed four people.''
The plane nose dived, flipped, and broke in two and came to rest upside down.
Mr Mitchell said it was his first beach landing since he began flying in 1989.
He and Paddy were held upside down in the cockpit by their seat belts.
Mr Mitchell feared the plane could ignite and unlatched Paddy's seat belt and door simultaneously and pushed him out.
Fighting shock, Mr Mitchell quickly exited the plane and called his fiance, Paddy's mother Debbie Smythe, to assure her they were all right and tell her where they had landed.
On the beach, the walkers he narrowly missed told him they never heard the plane until the impact.
When Ms Smythe arrived at the beach, her son was being loaded from a ute to an ambulance.
Ms Smythe said her fiance and son sustained seat belt ''burns'', had stiff and sore necks and shoulders but were all right.
Mr Mitchell said he was having flashbacks of the beach and remembered a low flying Air New Zealand ATR inspecting the crash scene.
Mr Mitchell said the insured plane was ''totalled'' and was transported in two pieces to Taieri Airfield by helicopter.
He hoped the Civil Aviation Authority investigation would reveal why the engine failed.
He had an engine fail before when he was flying a light plane in England about 15 years ago and crash landed in a turnip paddock.
In England, he returned to flying the next day and hoped to do the same today.
Mr Mitchell wanted to acknowledge the Emergency Services staff, the members of the public who helped and the pilots who trained him, giving him the skills to make an emergency landing.
