A man who aimed a laser light at the Nelson Marlborough Rescue Helicopter on its return from a late-night search was not operating under the cover of darkness as he thought.

The pilot and crewmen on the helicopter, returning to base at Nelson Airport around 2am on Wednesday, had a laser light shone at them. It is a criminal offence under civil aviation law because of the danger it presents to pilots.

Nelson Marlborough rescue helicopter pilot Jarrod Colbourne said the pilot and crewmen were returning from the Mt Owen search for tramper Alistair Levy when the incident happened.

They were able to locate the property near Three Brothers Corner and ultimately the man responsible by using the chopper's onboard Forward Looking Infra Red Unit.

"They were also able to use the unit, which is used to locate any heat source during a search, and the pilot could see the person walking around the balcony of the house," Mr Colbourne said.

Pilot Tim Douglas-Clifford said onboard intensive care paramedic Jon Leach, who was operating the infra red unit and therefore not wearing night-vision glasses, was most affected by the laser strike.

"We were able to pinpoint the property straight away," he said.

Mr Douglas-Clifford contacted the police, then hovered over the property for several minutes until they arrived at the house.

Police said a man had been summonsed to appear in the Nelson District Court in relation to the incident.

The Civil Aviation Authority said recently that laser illumination of aircraft was an offence because it could cause distraction, disorientation and discomfort for pilots resulting in a potentially hazardous situation during critical phases of flight.

Anyone who pointed a laser at an aircraft could be charged under the Civil Aviation Act with causing unnecessary danger. The maximum penalty for this offence was up to 12 months' imprisonment or a fine of up to $10,000.

The Nelson Marlborough Rescue Helicopter said the last 48 hours had been extremely busy with a total of eight missions flown, including medical, accident and search and rescue missions.

Helicopter rescue services were so stretched that St John Ambulance communications in Christchurch had to dispatch the Solid Energy Rescue Helicopter from Greymouth to transport a woman to Nelson Hospital after a car accident in the upper Buller Gorge just after noon yesterday.

A short time later the Nelson chopper was dispatched to the Falls River area in the Abel Tasman National Park, to a hiker with a suspected broken ankle.

The helicopter's onboard intensive care paramedic was winched down to the track to treat the 68-year-old tourist from the United Kingdom. Both she and her walking companion were then winched back into the helicopter before being flown to Nelson for medical treatment.

It followed the Nelson rescue crew's involvement in the search of the Mt Owen area for Mr Levy, and later the deployment of several LandSAR search teams into the Mt Owen area, to conduct a ground search.

A further mission was flown around 3pm yesterday to deploy an additional search team.

- © Fairfax NZ News