A helicopter pilot who sent and received cellphone text messages just before he was killed in a crash was not breaking any rules, authorities say.

The Civil Aviation Authority is looking into whether specific rules are needed around cellphone use following the crash that killed Morgan Saxton in 2008, and another death the year before where top-dressing pilot Andrew Wilde crashed while talking on a cellphone.

While laws are now in place to prohibit cellphone use by motorists, civilian pilots using visual navigation are not subject to the same restriction.

Mr Saxton died when his Robinson Helicopter Company R22 helicopter crashed into Lake Wanaka on November 1, 2008.

The Transport Accident Investigation Commission said there were no witnesses to the crash, but about six minutes before the accident, Mr Saxton flew past a barge skippered by a friend.

"Telephone company records showed that in the next few minutes the pilot had received and sent cellphone text messages, including one sent close to the estimated time of the accident to the barge skipper," it said.

The wreckage showed the helicopter was affected by a "mast bump", affecting the rotor, before it hit the water.

"If the pilot had been preoccupied with his cellphone, he would have had less time to take the appropriate recovery action," the commission said.

On the issue of cellphone use, CAA magazine Vector said: "Anecdotal evidence suggests that the use of cellphones by pilots is happening not just on private flights, and during agricultural operations, but also while on VFR [Visual Flight Rules] air transport operations."

The commission report into Mr Wilde's death in 2007 recommended the Director of Civil Aviation address the safety implications of the use of cellphones during "critical phases of flight" while operating under VFR.

CAA spokesman Bill Sommer said using a cellphone was "not good airmanship". But many aircraft now had cellphones or other communication devices built in. "We'll look at it as to whether, first of all, does there have to be a rule on this? Or is safety education going to apply?"

Armin Egli, the training manager at the Auckland Rescue Helicopter Trust, said if a cellphone was used by the trust, it would be by a crewman.

"There's always one pilot who is solely dedicated to what he's meant to be doing. We couldn't afford to get around the Auckland sky with those sort of distractions."