Cougar Helicopters uses Sikorsky S-92 choppers to transport oil industry workers offshore. (Cougar)

Cougar has again grounded a Sikorsky S-92 helicopter that was kept overnight on the Terra Nova oil platform after a cockpit indicator light warning earlier this week.

The company says an analysis by Sikorsky and further assessment led them to believe it could be “an early indicator of reduced performance.”

Cougar has decided to replace the helicopter’s gearbox. The work will take place over the coming days.

The chopper will go through a series of inspections and flight checks before being put back into full operation.

Cougar says Sikorsky’s monitoring system allows the company to identify component wear patterns, maintenance requirements, and issues that could affect multiple operators.

The rest of the Cougar fleet of S-92s is not affected.

“Cougar Helicopters, as continuously demonstrated, accepts nothing less than 100 per cent performance in its equipment,” company spokeswoman Candace Moakler said in an email to CBC News. “Cougar makes no compromise regarding safety.”

The indicator — a #2 input module chip light — illuminated while the Sikorsky S-92 was on approach to the floating oil production platform at about 9 a.m. Wednesday. The FPSO is anchored roughly 350 kilometres east of St. John's.

The crew of the chopper discussed the matter with Cougar’s maintenance centre after landing. They decided to shut the aircraft down and restart it, but the light remained on after that was done.

An engineer flew to the Terra Nova platform to assess the situation.

The helicopter — with two crew members and an engineer aboard — flew back to St. John’s on Thursday.

According to Cougar, modern aircraft like the S-92 are equipped with chip detectors in their lubricating systems to detect metal particles that could be in the engine, gearbox or hydraulic system.

They can provide an early indication of wear and act as a warning that maintenance may be necessary.