HALIFAX -- The Royal Canadian Air Force has grounded its fleet of CH-148 Cyclone helicopters after one of the naval choppers encountered a "severe bump" during a training flight -- the latest delay in a project years behind its original delivery date.

Col. Peter Allan, commander at the 12 Wing Shearwater air base, said the problem corrected itself during a descent and the pilot safely landed the aircraft with no damage during a night flight near Halifax on March 9.

However, the glitch prompted a freeze on flying as of March 12, and the Air Force is investigating with the help of aircraft manufacturer Sikorsky.

The Air Force also temporarily grounded the Cyclones in January to check for potential tail rotor problems following an incident on a North Sea oil platform involving a civilian version of the helicopter.

Allan said the latest problem isn't related to the tail rotor.

He said the Cyclone crew described feeling a "a severe bump on the underside of the aircraft."

"There were a couple of flight control system advisory lights that illuminated in the cockpit," he said.

A spokesman later indicated these included the "automatic flight control system advisory" and the "primary flight control system degraded advisory."

To date, 11 Cyclones have been delivered to the Royal Canadian Air Force, of which three are operated for testing and evaluation.

The existing fleet of aging CH-124 Sikorsky Sea King helicopters will continue to provide maritime helicopter support for the Royal Canadian Navy.

Doug Baker, a spokesman from the Maritime Helicopter Project, said he won't have a definite time when the fleet will fly again until the root cause of the incident is determined and potential fixes are identified.

He said the grounding means that flight testing is delayed, and that further delivery of helicopters from the Sikorsky plant before the summer will be on hold.

However, Allan said it's too early to predict if the problem will mean a delay in the Sikorsky helicopters being available for operational service.

In the meantime, technicians and air crew will continue training and flight simulators will be in use, he said.

The previous Liberal government signed a contract with U.S. defence giant Sikorsky to deliver 28 CH-148 Cyclone helicopters by 2008. The program has faced delays and technical challenges, resulting in two contract extensions.

Baker said after almost a month there is no result from the investigation of the latest issue.

"However ... the nature of the incident was very momentary," he said. "It was something that didn't exist once the aircraft was on the ground. It makes it difficult to isolate, duplicate and determine the root cause."