Air accident investigators fly out this weekend to probe the cause of a helicopter crash in the Atlantic Ocean that killed two Royal Navy flyers.

Flight Lieutenant Jenny Lewis, a former student of Newcastle University, is believed to be the first woman pilot to die while serving with the British fleet.

The 25-year-old, and her pilot Lieutenant Rod Skidmore, 39, died when their Lynx aircraft came down on Wednesday about 200 miles off the coast of Virginia in the US.

A third crew member, Paul Hanson, a petty officer working as a photographer, escaped with minor injuries after being thrown clear as the craft hit the water.

Preliminary investigations have already been carried out by members of the officers' ship, HMS Richmond, but a Board of Inquiry is expected to fly out to the vessel within the next 48 hours to compile a more thorough report.

A Royal Navy spokesman said that "no stone will be left unturned" to determine the cause of the crash, which happened as the Lynx returned to the ship after taking part in weapons trials.

"We're dealing here with the human condition and tragedy. People want to know what happened," he said.

The search has now been called off and the helicopter is believed to be lying in 4,000m of water.

A salvage operation could be mounted to raise the 15-year-old aircraft, which is thought to have come down because of engine failure, the spokesman added.

''We have been asked about safety. As far as we are aware, there is no issue of safety with the Lynx or indication about defects which could be proven in other aircraft," he said.

HMS Richmond, which was the last Royal Navy frigate built at Swans on the Tyne, has strong ties with Richmond in North Yorkshire, and its crew are due to visit the market town this summer.

Senior officers at the flyers' base, the Royal Navy Air Station at Yeovilton, Somerset, also praised their skills.

Commanding Officer Tony Cramp said: "The pair of them were extremely diligent, professional aviators."

Flt Lt Lewis was one of three women from 40 members of 815 Naval Air Squad-ron and was said to be talented with a bright future.

She was working as an navigator-observer when the helicopter crashed, after making an emergency call at low altitude about 40 miles from the ship in fair weather conditions