Flight control software glitch haunted Cyclone helicopter during trials

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.

Six Canadian service members died in the crash. Clockwise from top left: Capt. Kevin Hagen, Sub-Lt. Abbigail Cowbrough, Capt. Brenden Ian MacDonald, Master Cpl. Matthew Cousins, Sub-Lt. Matthew Pyke, Capt. Maxime Miron-Morin. (Department of National Defence)

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 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.

Flight restrictions

Those restrictions, among other things, barred the aircraft 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.

“It’s more of a technical restriction and avoiding certain pieces of the code, really, in the software, making sure we don’t induce a fault,” Col. Peter Allan, commander of 12 Wing Shearwater in Nova Scotia, said at the time. (He was quoted in the aviation publication Global Flight.)

“Sikorsky has narrowed down very specifically what pieces of code are affected in the software and how we would induce those pieces of code to be triggered.”

A tight timetable

The Cyclone software was upgraded on at least 14 of the 28 Cyclones ordered by the air force, including the one that crashed off Greece in late April. The work on the aircraft was on a tight timetable because the air force had started to retire the CH-124 Sea King maritime helicopters after over five decades of service.

The Department of National Defence (DND) was asked recently whether any restricted flight certificates were still outstanding, or if the Cyclones had any limitations imposed on their operations.

“There have not been any additional restrictions added to the fleet following the crash as the investigation is still ongoing,” said Dan LeBouthillier, head of media relations, in an email.

“However, as with every other aircraft in the RCAF inventory, the CH-148 Cyclone is subject to technical limits imposed by the original aircraft manufacturer as well as by operational limits imposed by the RCAF.”

LeBouthillier listed some of those technical limits — which cover things like the inadvisability of operating the aircraft in climates where the temperature exceeds 47 degrees Celsius, and the proper way to fold its rotors.

An ‘operational pause’

DND also refused to say whether the aircraft was observed suddenly pitching forward and accelerating into the ocean.

“As any information of this nature is part of the flight safety investigation, we will not be discussing them publicly in order to ensure the integrity of our investigative efforts,” LeBouthillier said.

An “operational pause” was imposed on the entire Cyclone fleet after the crash; essentially, the fleet is grounded again while investigators analyze data from the aircraft’s twin flight recorders. Last week, Defence Minister Harjit Sajjan said the investigation could take a year or more.

Michael Byers, a University of British Columbia defence policy analyst who has written reports and articles critical of the maritime helicopter program, said the software fault could be important if investigators end up ruling out pilot error.

‘No time to respond’

Because the aircraft was flying close to the ocean’s surface, 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 (FBW) 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 federal government and DND have an obligation to be more transparent about the accident and the investigation, he added.

DND slow to disclose facts

The first reports of the accident came from local media and Greece. It was NATO — not the Canadian government — which initially confirmed the aircraft had gone down.

In subsequent public statements, DND downplayed the notion that the helicopter crashed close to HMCS Fredericton — and the fact it happened in front of witnesses was withheld entirely for almost a week after the accident.

“This is about the safety of the aircrew,” Byers said. “I cannot see how the Canadian government could withhold information.”

The federal government recently was still trying to figure out how to recover the wreckage, and the remains of missing crew members, from water about 3,000 metres deep.

A repatriation ceremony for six military members killed in a recent helicopter crash was held at CFB Trenton on Wednesday. 1:59

The body of Sub-Lt. Abbigail Cowbrough was recovered the day of the crash. Partial remains belonging to Capt. Brenden Ian MacDonald also have been retrieved.

Still missing are the remains of Capt. Kevin Hagen, Master Cpl. Matthew Cousins, Sub-Lt. Matthew Pyke and Capt. Maxime Miron-Morin.

The National Post reported Tuesday that the federal government was in talks with the U.S. about using some of its deep diving technology to retrieve the aircraft.

CBC News asked DND on Monday about the status of the salvage operation. In a statement issued late Tuesday, the department said no decision had been made.

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