Police investigate Qld helicopter crash

A man is "lucky to be alive" after a helicopter allegedly hit powerlines while mustering cattle in southern Queensland.

Police say the man - aged in his 20s - was the only occupant of the helicopter which crashed at a Grosmont property in the Western Downs region at about 9.30am on Thursday.

Police believe the helicopter struck a powerline before it went down near Ryals Road and Perretts Road.

The man suffered serious chest injuries but it is believed he was able to remove himself from the "significantly damaged" helicopter before emergency services arrived.

He was airlifted to Toowoomba Hospital in a serious but stable condition, the RACQ LifeFlight Rescue said.

"He's lucky to be alive," RACQ LifeFlight Rescue pilot Hamish Felton-Taylor said.

The Forensic Crash Unit are assisting.