Air force returning Cyclone choppers to service soon as investigation focuses on flight software
Director of flight safety calls crash an 'unavoidable accident'
Through a haze of technical jargon, senior air force commanders painted a stark picture Tuesday of the last desperate moments of Stalker-22, the CH-148 Cyclone helicopter which crashed in the Ionian Sea on April 29, killing six military members.
After conducting a low flypast of HMCS Fredericton, the aircraft was turning under the semi-autonomous control of its fly-by-wire computer system when a software "bias" told the helicopter it wasn't moving fast enough.
The computer pitched the nose downward and sped the aircraft up. Investigators suggest the pilot may have tried to manually override the computer and pull up from what had become a swift, fatal dive into the ocean.
Watch: Investigator is asked whether computer was flying chopper when it crashed
It is on the basis of this information, gleaned mostly from the Cyclone's flight data recorder, that the air force has cleared the helicopter to resume service almost immediately.
The air force says it plans to introduce enhanced training for flight crews and new flying restrictions as the investigation into the crash digs deeper for the root cause of the software issue — which the officer in charge of the investigation steadfastly refused to characterize as a glitch.
"The term of a software glitch, that is a bit ... that's a challenging statement to use, because we need to understand the design specifications of what we were wanting those flight control laws to do," said Col. John Alexander, the air force director of flight safety.
Watch | RCAF investigator is asked whether a software 'glitch' caused the Cyclone crash
That statement is significant because it suggests investigators don't know for certain whether they're dealing with a flaw in the Cyclone's flight control computer programming, or with something that might have been overlooked in the specifications when the software was developed.
Alexander acknowledged the aircraft was flying in a semi-autonomous mode — known as the Automatic Flight Control System (AFCS) — as it approached the patrol frigate off the coast of Greece late in the afternoon of April 29.
The aircraft was losing speed in its turn when the computer apparently determined the aircraft wasn't moving enough. The pilot punched in manual commands, but they were "outside of the tested aircraft spectrum," Alexander said.
'An unavoidable accident'
That means the helicopter software did not recognize the pilot's instructions and chose to ignore them — something "for which the crew would have had no previous experience, nor exposure prior to this event," he added.
It was "an unavoidable accident," Alexander said.
The commander of the 1st Canadian Air Division, Lt.-Gen. Alain Pelletier, cautioned that the investigation still has a long way to go before it has a definitive conclusion.
The information collected so far, however, is enough for the air force to resume Cyclone flying operations within the coming days.
"I assure you, the decision was not taken lightly," said Pelletier.
"I have full confidence in our personnel at 12 Wing Shearwater [Nova Scotia] and their ability to resume flying activities in a safe manner."
The air force expects to get training completed and the fleet up to speed in the next week or so.
Still, the investigation to date has raised some uncomfortable questions about whether the Cyclone — a heavily militarized version of the Sikorsky S-92 — was ready for service when it formally replaced the five-decade-old CH-124 Sea King.
It also raises questions about the certification of the Cyclone by Canadian air safety inspectors.
Brig.-Gen. Nancy Tremblay, director-general of the air force's technical airworthiness authority, suggested she was confident the certification process caught everything.
"The information from the investigation so far about the accident on the 29th of April is absolutely unrelated to any previous issues that you would have heard concerning the Cyclone fleet," she said.
The air force has asked the manufacturer to confirm there are no other "software biases."
That's significant because, in 2017, during the run-up to the Cyclone's introduction to service, one aircraft experienced a software "glitch" which caused all three flight control computers to momentarily reset while a helicopter was in the air over Nova Scotia.
The aircraft dropped suddenly in altitude before the pilots recovered. The incident led to a nine-week grounding of the fleet and was addressed through a software update.
Watch | The military's long quest to replace its maritime helicopters
The Canadian military, with the help of a U.S. Navy underwater salvage drone, was able to spot the wreckage of the Cyclone in over 3,000 metres of water and recover selected pieces of the aircraft as well as some remains.
In the immediate aftermath of the crash, the body of Sub-Lt. Abbigail Cowbrough and the partial remains of pilot Capt. Brenden Ian MacDonald were recovered and identified.
Capt. Kevin Hagen, Capt. Maxime Miron-Morin, Sub-Lt. Matthew Pyke, and Master Cpl Matthew Cousins were recorded as missing.
- An earlier version of this story stated that a preliminary report blamed the crash on "aircraft system and human factors." In fact, the report cited those as possible causes.Jun 16, 2020 11:16 AM ET