The Transportation Safety Board (TSB) said without a flight recorder, there is no way to be sure what caused a plane crash that killed four people, including former Alberta premier Jim Prentice.
“We don’t like having to say we don’t know when asked what caused an accident or why, we want to provide definitive answers to the victim’s families, to Canada’s aviation industry and to the Canadian public,” TSB chair Kathy Fox said.
WATCH: The Transportation Safety Board has renewed calls to make flight recorders mandatory in all non-commercial aircraft across Canada. Bindu Suri explains why.
The plane crash happened on Thursday, Oct. 19, 2016. The Cessna Citation 500 took off from Kelowna International Airport at 9:32 p.m. destined for Calgary/Springbank Airport.
The plane disappeared off the radar and crashed eight minutes later in Winfield, 11 kilometres away. Everyone on the plane — Prentice, pilot Jim Kruk, Dr. Ken Gellatly and Sheldon Reid — died.
READ MORE: TSB officials say no indication of distress call in plane crash that killed Jim Prentice
“After countless hours of analysis from experts pouring over wreckage, radar data and company and personnel records, we aren’t much closer to knowing with certainty what caused this accident,” Fox said.
“We have no flight recorder, we have no voice recorder, they were not required by regulation and therefore we have no detailed sequence of what went on in the flight deck.”
WATCH: The TSB said investigators haven’t been able pinpoint why the small aircraft crashed on Oct. 19, 2016. As Julia Wong reports, experts are calling for changes in flight requirements.
On Thursday, the board said the most plausible guess is that pilot Kruk, who was flying the plane alone, “experienced spatial disorientation and departed from controlled flight shortly after takeoff.”
The report found that shortly after departure from Kelowna, the aircraft entered a steep descending turn to the right until it struck the ground. No emergency call was ever made.
“The radar data, which offer much less detail than flight data recorders, show that the aircraft experienced rapid changes in the initial rate of climb from 4,000 feet per minute down to just 600 feet per minute, then increasing to 6,000 feet per minute, all within 30 seconds,” TSB senior investigator Beverely Harvey said.
WATCH: The TSB explains how frustrating it is to not have the data to provide answers to the cause of the crash.
Harvey said Kruk was an experienced pilot, but the investigation showed he didn’t have a lot of experience flying at night, with two takeoffs in the previous six months before the crash.
“This did not meet Transport Canada requirements to carry passengers at night,” Harvey said. “Pilots who do not have sufficient night proficiency are at a greater risk of experiencing spacial disorientation.”
READ MORE: Jim Kruk, ‘avid aviator’, identified as 4th person killed in BC plane crash
However, Harvey reiterated that without “hard data” investigators can not know for certain what happen that night.
“Spatial disorientation can happen during the day in cloud as well as at night, but when you’re at night and in cloud, the pilots are totally dependent on their instruments to tell them what’s up and what’s going on,” Fox explained.
“Therefore, pilots can be more susceptible to spatial disorientation at night and in cloud.”
WATCH: Kathy Fox explains the phenomenon of spatial disorientation
Because of the undetermined cause, the TSB is recommending the mandatory installation of lightweight flight recording systems by all commercial and private business aircraft operators not currently required to carry them.
The board can recommend change, but can’t mandate it. That’s the job of Transport Canada.
“We’ve seen the benefits in Les lles de Madeleine that a flight recorder can have in terms of helping the TSB determine what happened and why,” Fox said.
“If we don’t know what happened and why then those who need to make changes to prevent similar accidents in the future don’t know what actions to take.
WATCH: TSB calls on Transport Canada to start mandatory installation of data recorders in commercial and private business aircraft.
The TSB also raised concern with the way transport Canada oversees private business aviation in the country. No records were found that indicated this aircraft had ever been inspected by Transport Canada.
WATCH: Kathy Fox says Transport Canada should require all operators to have systems and should be inspecting them.
Transport Minister Marc Garneau thanked the TSB for its work on the investigation.
“The first thing I want to say is to express my sympathies to those who lost their lives in this tragic air accident,” he said. “Of course, all of us know Jim Prentice was one of those people. I got to know Jim and had the greatest respect for him.
“I will remind everybody that soon after this accident occurred, I did announce that Transport Canada would be looking at the question of event recorders in medium-sized commercial aircraft and that work is well underway,” the minister said.
“We’re looking at it from the point of view of technology, we’re looking at it from the point of view of survivability, cost — all of those factors are being taken into account. We decided to follow up on that because we felt it was important. I understand the TSB is also talking about not only commercial aircraft now, but also private aircraft, and we’re doing that.”
Garneau was asked why mandating event recorders in planes was taking so long.
“These things are sometimes very complex to look at — technology, cost, survivability — those are big issues and we have to look at them very, very carefully and we’ve also been waiting for the report from the TSB.”
READ MORE: Light rain, good visibility when plane crashed, killing former Alberta premier Jim Prentice
The family of Jim Prentice issued a statement, thanking the TSB for its work on the report and recommendations.
“While this report cannot restore what has been lost, it is our hope the learnings from this tragic event can be used to prevent similar accidents in the future,” the statement read.
The family added they are proud of Prentice’s accomplishments, both as a family man and as a politician, and that they will always miss him. They also offered their thoughts and prayers for the other families involved in the crash.
The complex investigation included trying to reconstruct events leading up to the crash, sending pieces of the plane to a TSB lab in Ottawa for analysis and looking at drone footage from the scene. The pilot’s training, qualification, proficiency records and medical history were also part of the investigation.
WATCH: Extensive coverage of the plane crash that took four lives, including that of Jim Prentice.