Police are interviewing a man over an attack on an army helicopter at Rockhampton airport in central Queensland.

They say the man made his way onto the tarmac shortly after 9:30am (AEST) and damaged the aircraft.

It is believed he allegedly used a mattock or axe on a Tiger helicopter, as a protest against the joint US and Australian military Exercise Talisman Sabre.

Police say he is yet to be charged.

The attack comes as a Rockhampton magistrate fined three protesters for trespassing in the Shoalwater Bay training area.

Two men and a woman pleaded guilty to trespassing in the training area, where Exercise Talisman Sabre is being held.

The peace protesters were detained by troops near the Samuel Hill airfield yesterday.

The magistrate fined 46-year-old Margaret Pestorius $750, 24-year-old Andy Paine was fined $600, and 39-year-old Robert Jones received a $500 penalty.

Ms Pestorius denies they were putting their lives at risk.

"We took safety very seriously - we had a GPS, we had a compass, we made sure that we knew where we were," she said.

"It's very benign country, it's beautiful Darumbal Country.

"We weren't in the live-fire areas ourselves, but we were looking for other ways of disrupting."