The CH-148 Cyclone helicopter has what the air force calls a "triple redundant" flight control system — and during a 2017 training mission off Nova Scotia, all three of those computers momentarily failed at once.
It was a major software glitch, alarming enough to ground the fleet for nine weeks.
At the time, the military described the incident publicly as a "severe bump" which reset the controls and caused the aircraft to briefly and suddenly lose altitude. The pilot managed to recover and land safely.
One defence expert now says that incident may prove to be vitally important as investigators probe the cause of last month's Cyclone crash in the Ionian Sea. The crash, which happened while the chopper was taking part in NATO operations, claimed the lives of six Canadian service members — four aircrew and two sailors.
Chopper 'flew into the ocean,' say sources
Multiple defence sources tell CBC News that at the time of the crash, the Cyclone was conducting a high-speed, low-level photo pass of HMCS Fredericton, a manoeuvre known in the air force as a "Brownie Run" after a NATO standard camera.
Without warning, the helicopter suddenly pitched forward and "flew into the ocean," said the sources, who were granted anonymity because of the sensitivity of the investigation.
The March 9, 2017 incident involving a software glitch aboard a Cyclone is a matter of public record. What wasn't fully revealed at the time, the sources said, was the fact that all three interconnected computers inexplicably reset themselves — something that could have led to a catastrophic crash.
When the nine-month grounding of the fleet ended three years ago, the Cyclones continued to operate for a period of time under a series of flight restrictions while their manufacturer, Sikorsky Aircraft, addressed the software issue through a pre-planned upgrade.
Military Aircraft Every type from fighters to helicopters from air forces around the globe
Classic Airliners Props and jets from the good old days
Flight Decks Views from inside the cockpit
Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior
Cargo Aircraft Pictures of great freighter aircraft
Government Aircraft Aircraft flying government officials
Helicopters Our large helicopter section. Both military and civil versions
Blimps / Airships Everything from the Goodyear blimp to the Zeppelin
Night Photos Beautiful shots taken while the sun is below the horizon
Accidents Accident, incident and crash related photos
Air to Air Photos taken by airborne photographers of airborne aircraft
Special Paint Schemes Aircraft painted in beautiful and original liveries
Airport Overviews Airport overviews from the air or ground
Tails and Winglets Tail and Winglet closeups with beautiful airline logos