Key Points:

A 49-year-old pilot is in a critical condition at Hawke's Bay hospital after his helicopter hit power lines and crashed this afternoon.

His Robinson R44 helicopter crashed on farmland north of Napier, just after midday.

A Hawke's Bay hospital spokeswoman told NZPA tonight the pilot was in the intensive care unit in a critical condition.

It was earlier thought his injuries were not serious as he had been able to communicate with his rescuers.

Eastern districts police communications manager Kris McGehan said police were alerted at 1.15pm when the Heliworks chopper failed to return from a 12-minute spraying mission.

Search and rescue teams found the helicopter about 2pm on a farm near a swamp.

The local pilot was the only person on board, Ms McGehan said.

A Lowe rescue helicopter spokesperson said the pilot hit a wire while he was spraying.

Police, the Fire Service and St John's staff helped extract him from the wreckage.