The US Navy has offered to help Canada recover this helicopter which crashed in the Ionian sea with six aboard. Credit: RCAF.

The CH-148 Cyclone helicopter (Call sign ‘Stalker”) had lifted off from the Halifax class frigate HMCS Fredericton with six aboard — four aircrew and two sailors — on a classified mission as part of a NATO task force in the Mediterranean.

Multiple sources told the CBC that the anti-submarine helicopter was on its way back to the ship on April 29, when it prepared to conduct a high-speed, low-level photo pass, a manoeuvre known in the air force as a “Brownie Run,” named after a NATO standard camera.

It would never make it — about two miles away, and in full full of horrified shipmates who were set to receive it, it plunged into the Ionian Sea off the coast of Greece, killing all on board.

A flight-investigation team is studying the causes of the crash and is expected to present preliminary findings in the coming weeks, though a full report is not expected until next year.

Meanwhile, the helicopter crashed in water roughly 3,000 metres deep, which is complicating efforts to recover the aircraft.

Cue the US Navy, which is contributing a Remora III salvage remotely operated vehicle to the recovery attempt — a capability the Canadian Armed Forces doesn’t have.

The remains of Sub-Lt. Abbigail Cowbrough and partial remains of Capt. Brenden Ian MacDonald have been recovered and identified. Capt. Kevin Hagen, Capt. Maxime Miron-Morin, Sub-Lt. Matthew Pyke, and Master Cpl. Matthew Cousins are missing and presumed dead.

“An operation of this nature is not without challenges, and factors like weather and sea-state could cause delays,” said Rear Admiral Craig Baines, commander of Maritime Atlantic Forces.

“It goes without saying that until our team is on site and the search begins, we cannot speculate on what they may or may not find or how long the operation will ultimately take.”

According to the CBC, one expert nows says a 2017 incident may prove vitally important as investigators probe the cause of the crash. In that case, the Cyclone suffered the failure of its “triple redundant control system” — all three of those computers momentarily failed at once — causing it to suddenly lose altitude.

Thankfully, the pilot managed to recover and land safely. It was a major software glitch, alarming enough to ground the fleet for nine weeks.

Following that investigation, restrictions were applied and the aircraft was barred from practice manoeuvres close to the ground, sloped landings and hoisting equipment and personnel.

The limitations were meant to address the pitch and roll of the aircraft and only applied at certain altitudes and in specific flight control modes.

RCAF officials said the Cyclone’s flight-data and voice recorders have been recovered and are being analyzed by the National Research Council, but most of the wreckage remains on the sea floor nearly two miles deep.

The Phoenix International Remora 6000 ROV is a 6,000 meter-rated work-class vehicle developed for deep ocean salvage, search and broadcast-quality optical documentation.

There are two Remora ROVs: Remora II and Remora III, according to Jane’s. The Remora III is larger, heavier and has more vehicle power than Remora II.

The Phoenix International Remora 6000 ROV is a 6,000 meter-rated work-class vehicle developed for deep ocean salvage, search and optical documentation. Credit: Phoenix International.

Both Remora ROV systems use an industry proven fiber optic cable, have state-of-the-art sensors and telemetry systems, and are equipped with dual manipulators.

The compact design allows these systems to be transported by air or sea, and quickly mobilized aboard vessels to provide support for a wide range of underwater tasks.

Both configurations offer small physical size coupled with axial lateral thruster geometry permitting precisely controlled maneuvers in the tightest of spaces.

“We’ve determined that the most rapid response capability was resident in the US Navy,” Lt.-Gen Mike Rouleau said during a briefing on Parliament Hill.

“Speed in this search and recovery is very important for a number of reasons. The first is for the families. The second relates to our RCAF ethos: We do not leave our fallen behind. And the third reason is because the environment will degrade evidence over time.”

The search site is in the Ionian Sea about 220 nautical miles east of Sicily.

The underwater locator beacon will potentially assist with locating the aircraft, although the RCAF said it would not know if the beacon was still working.

Michael Byers, a University of British Columbia defence policy analyst, said the software fault could be important if investigators end up ruling out pilot error.

Because the aircraft was flying so low, he said, it would have been in a vulnerable position and the two pilots would have been left with very little time to react.

“If you are just a few hundred feet above the water, you have no time to respond,” he said.

Another question investigators will have to address is whether there were other undetected flaws in the Cyclone’s fly-by-wire software, Byers said.

“We don’t know exactly what happened, but [information to date] suggests a change in the flight control system … something went wrong, either a computer problem or perhaps a pilot error, but that seems unlikely,” he said.

The Remora III retrieved the black box 3,900 metres deep from an Air France jet that crashed in the Atlantic in 2009, killing all 228 people aboard.

Sources: CBC, CTV, Jane’s, Phoenix International