A Cougar helicopter was grounded on an oil rig Wednesday because of what was believed to be a problem with its autopilot system.

A spokesperson for Husky Energy said the crew were doing pre-flight checks on the Henry Goodrich oil platform around 9:30 a.m. when there was a problem with the chopper's "Stability Augmentation System."

Cougar tried to send a maintenance engineer to the platform, but the helicopter was forced to turn back because of fog.

The grounded Sikorsky aircraft stayed on the rig overnight while workers returned to St. John's on an offshore supply vessel.

The Husky official said there were no flight safety issues at the time.

The incident comes at the heels of a Transportation Safety Board investigation that found pilots are too dependent on the autopilot systems.