After he told his mum what happened, she took him to Palmerston North Hospital, where his arm - broken, as it happened - was seen to.
The doctor heard about the tree. He had heard about the fall.
"What were you trying to do, young fellow?" the medic asked, not unkindly. "Fly?"
The lad nodded sheepishly.
Funnell, 66, recalls the telling moment in his gripping autobiography Rescue Pilot, released tomorrow.
The book covers his action-packed career as one of New Zealand's best known helicopter pilots.
For almost 50 years Funnell was called out to some of the country's high-profile rescues, as well as day-to-day retrievals of accident victims, stranded trampers and desperately ill patients.
His deeds of derring-do would not be out of place in the pages of Boy's Own magazine. It is a classic tale of an ordinary Kiwi bloke doing extraordinary things. But he likes to downplay his daring exploits.
"People think I have had this thrilling and exciting life," he tells the Herald on Sunday. "But often it was just hours of boredom mixed with moments of terror.
"The biggest satisfaction has come from helping people, knowing we could make a difference to a patient and often saving their life."
Funnell is perhaps best known for the unprecedented 3600km return mission to save a MetService scientist savaged by a shark on the remote subantarctic Campbell Island in 1992.
He set off at night knowing the distance was twice the helicopter's fuel range. He was later awarded a New Zealand Bravery Medal.
He has also been behind the headlines of iconic moments - such as chasing a plane stolen by an anti-apartheid protester believed to be intent on crashing into the 1981 All Blacks v Springboks rugby match in Gisborne.
The father-of-two also flew the TV news reporter attempting to track down Sir Bob Jones for an interview. The reporter was punched in the face by the irate New Zealand Party founder who was trying to do a spot of quiet fly fishing in Turangi.
Taupo-based Funnell has seen and done it all.
He dealt with the hijacking of a chopper by an anti-1080 activist, plucked frostbitten skiers from avalanches and blizzards and assisted in the disaster relief operation after the Boxing Day tsunami in Banda Aceh in 2004.
Then there is the sombre task of recovering bodies from plane crashes and boating and hunting accidents. In his time, Funnell has played a vital role at that critical juncture between life and death.
"The way I see it, I was just a taxi driver - an Uber driver, if you like," he says, with a hint of dark humour.
"You call, we haul. The people we went to rescue were literally dying to meet us and no one ever complained about the service."
But what drives someone to risk his life time after time to help people in often grim and dangerous situations? What makes someone like Funnell tick?
"My family think I am unhinged, quite mad really," he says. "Perhaps there is more than an element of truth in that. But although a lot of the missions I was involved in appeared to be dangerous, I didn't see things that way.
"I am flying a crew of people to these rescues, often in bad weather or under tricky circumstances.
"Yes, there is a recognised element of danger but this was managed at all times. It was never a case of staging a rescue at any cost.
"Anyone flying with me was ¬always asked if they had any concerns and if they did, to speak up.
"If you are in a position where you are fearful of the situation you are getting involved in it means you have gone too far and it is time to give yourself a good shake.
"Everything I did was well thought out and risks were calculated. If I thought I was putting my own or other crew members' lives on the line, I would never go."
After the dramatic Campbell Island rescue, Funnell was awarded the Citation for Bravery, but he doesn't like the tag "hero".
"The heroes are the people who ride in the back with me and did all the work," he says.
"They are the ones who put their trust in me and that we made the right decisions.
"They are the ones who actually save lives."
Growing up in Manawatu, Funnell first saw an aeroplane up close when a Tiger Moth landed at a local sports day.
He left school at 16 and spent two weeks at the nearby Walsh Memorial Scout Flying School.
He was at the controls within three days.
He then spent a couple of years working for his father on the family farm, but kept up the flying lessons and in 1969 gained his private pilot's licence, followed by his commercial licence. A move into aviation was inevitable.
He completed his agricultural pilot training in Taihape and two years later started flying helicopters in Dannevirke.
John and his then wife Trish shifted to Taupo in 1978 where he worked for Helicopters New Zealand building the Turoa Skifield, before moving into search and rescue.
Back then, people outside the cities who needed urgent hospital care were usually transferred by ambulance, which could mean a wait of several hours.
"At first we were only really transporting people to the road's edge where they would then get picked up by an ambulance," he says. "But then it was realised just how quickly a chopper can get a person to hospital and the whole game changed."
Not everyone could be rescued. Some people died before the chopper arrived, or afterwards.
"The satisfaction you get from getting a positive outcome for someone stuck in a bad situation is immense but you can't save everyone.
"When children are involved and have been killed or hurt as the result of violence or an accident, it is particularly hard to take.
"They are the ones I still have difficulty with."
Funnell - who survived a brain tumour in 2001 - called time on his search and rescue career at the end of last year.
He lives with his new partner in Taupo but is not ready to put his feet up yet and still runs a farm, a hotel and a beekeeping business.
He also still pilots helicopters for fun and is happy to help people out when he can.
"I started back in the days when flying was dangerous and sex was safe," he says, with a grin. "Now it is the other way around.
"Of course, I miss search and rescue terribly and the main thing I miss is helping people. You can't put a price on something like that."
