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Dorval, Quebec, 17 August 2016 – The Transportation Safety Board of Canada (TSB) investigation report (A13Q0098) released today shows that fuel exhaustion led to the forced landing of a Beechcraft King Air 100 in a field near the St-Mathieu-de-Beloeil Airport, Quebec, in June 2013. The TSB also identified deficiencies in the pilot’s performance and the company’s supervision of flights, as well as weaknesses in Transport Canada’s (TC) process for approving operators’ appointments of operations management personnel and in the regulatory oversight of flight operations.

On 10 June 2013 at 1700 Eastern Daylight Time, a Beechcraft King Air 100 operated by Aviation Flycie Inc. took off from the Montréal/St-Hubert Airport (CYHU), Quebec, with one pilot and three passengers on board for a test flight. While on its way back to the airport, 24 minutes after take-off, the aircraft ran out of fuel. The pilot decided to divert to the St-Mathieu-de-Beloeil Airport. When the pilot realized that the aircraft would not reach the runway, the pilot attempted a forced landing in a field near the airport. The forced landing ended in an aerodynamic stall and the aircraft struck the ground 30 feet short of the selected field. The aircraft was extensively damaged, and the four occupants sustained minor injuries.

While preparing for the flight, the pilot relied exclusively on the fuel gauges, misread them, and assumed that the aircraft had enough fuel on board for the flight. During the flight, the pilot did not monitor the fuel gauges and, when returning to the airport, decided to extend the flight to practise a simulated instrument landing approach, without noticing there was insufficient fuel to complete it.

The investigation found the pilot had a history of performance that did not meet expected standards to act as pilot-in-command for that aircraft type. Despite a marginal performance during the check flight, the pilot had successfully passed a pilot proficiency check, and TC had approved the individual's appointment to the position of chief pilot.

Meanwhile, the company's operations manager, who had no previous experience in commercial air carrier operations, was unable to fully appreciate the significance of the chief pilot's marginal performance or to detect deviations from regulations in the commercial flights performed over the company's first three months of operations, which preceded the accident. TC had also approved the appointment of the operations manager.

In addition, the investigation revealed that the person responsible for maintenance (PRM), a new co-pilot on the company's BE10, had no previous experience in maintenance or in air taxi flight operations. TC had also approved the appointment of the PRM.

The TSB determined that TC's appointment approval process was not effective and that, once the appointments had been approved, the management team's inability to perform the duties and responsibilities was not grounds for TC to revoke them.

The TSB has identified safety management and oversight as a Watchlist issue. As this occurrence demonstrates, some transportation companies are not effectively managing their safety risks. The Board has been calling on TC to implement regulations requiring all operators in the aviation industry to have formal safety management processes, and for TC to oversee these companies' safety management processes.

See the investigation page for more information.

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Edmonton, Alberta, 11 August 2016 – In its investigation report (A15W0069) released today, the Transportation Safety Board of Canada (TSB) found that during firefighting operations, the aircraft encountered a fire whirl, which led to a loss of control and impact with terrain. The pilot was fatally injured in the accident, which occurred near Cold Lake, Alberta, on 22 May 2015.

The Conair Air Tractor AT-802A Fire Boss was operating as Tanker 692 in support of wildfire management operations 25 nautical miles northwest of Cold Lake. It was the last in a formation of four Fire Boss aircraft that had just completed two drops on the northern edge of the fire. The tankers were conducting their drops at a specified bombing height of approximately 150 to 200 feet above ground level (agl), and after releasing their loads, the aircraft would climb back up to the circuit height of approximately 1000 feet agl. As Tanker 692 was coming out of its third drop, it encountered severe turbulence, which caused the aircraft to enter an undesired nose-up attitude, then roll to the left and pitch nose-down. The aircraft's low altitude while fighting the wildfire made recovery improbable, resulting in impact with the terrain.

The investigation determined that the aircraft had encountered a tornado-like event generated by the fire, which is known as a fire whirl. A number of factors such as a large heat source, unstable atmosphere, and low winds can cause a fire whirl. When Tanker 692 completed its third drop on the fire, the pilot could not see the fire whirl and would not have anticipated it being in the flight path.

The investigation found that if fire behaviour training is not provided to personnel involved in fire-suppression activities, there is a risk of aircraft being flown into unsafe conditions. The investigation also found that not all types of restraint system adequately protect pilots from the effects of severe turbulence, although this did not contribute to the accident.

Following the occurrence, Conair Group Inc. commissioned a fire behaviour study to look into the environmental conditions during the occurrence, and contracted a study into the accident. In addition, the company added a session to its training program focused on awareness of environmental conditions and the dangers around forest fires. It also conducted an operational review and installed five-point harnesses in its AT-802 fleet.

See the investigation page for more information.

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Dartmouth, Nova Scotia, 5 August 2016 – The Transportation Safety Board of Canada (TSB) is issuing a clarification concerning investigation report M15A0189, which it released on 2 August 2016. It emphasizes that the accident and fatality statistics for commercial fishing vessels data in Table 3 of the report, are for Newfoundland and Labrador, not for Canada as a whole.

From 2000 to 2015, there were 31 commercial fishing-related fatalities in Newfoundland and Labrador, and 189 in Canada.

Loss of life on fishing vessels is an issue on the TSB's Watchlist, and the Board completed a Safety Issues Investigation into fishing safety in 2012. The Board continues to call for concerted and coordinated action by federal and provincial authorities and by leaders in the fishing community to improve the safety culture in fishing operations.

See the investigation page for more information.

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Dartmouth, Nova Scotia, 2 August 2016 – In its investigation report (M15A0189) released today, the Transportation Safety Board of Canada (TSB) is again emphasizing the wide range of safety risks that persist for small fishing vessels.

On the evening of 16 June 2015, the small fishing vessel CFV 130214, an open boat with three people on board, was reported overdue from a crab fishing trip in Placentia Bay, Newfoundland and Labrador. Joint Rescue Coordination Centre Halifax initiated a search, and the bodies of all three crew members were found the next day on Bar Haven Island. The crew members were not wearing personal flotation devices. The vessel was not found and is believed to have sunk.

As the vessel was lost at sea and there were no witnesses or survivors, the investigation could not determine with certainty the primary cause or causes of the occurrence.

With only a few weeks left in the fishing season and none of his crab quota filled, the master was under increased pressure to fish. The master had modified a smaller secondary vessel, a 7.1-metre open boat, to use for crab fishing while his primary vessel was under repair, but the modifications were not assessed or tested for stability. The investigation found that the added weight from the modifications, combined with the weight of the crew members, bait, ice, and the catch on board would have significantly reduced the vessel's freeboard, making it more susceptible to taking on water, with a negative impact on the vessel's stability. Deteriorating weather and sea conditions put the heavily loaded vessel at further risk of taking on water.

To lease another vessel, the master would have had to formally ask the Department of Fisheries and Oceans (DFO) for an exemption from the Fisheries Licensing Policy for the Newfoundland and Labrador Region. It could not be determined why the master did not do so, or whether the request would have been approved. It also could not be determined whether the master fully understood that an exemption was an option or how he might have obtained one. The investigation found that there was no information about the exemption on the DFO website or in any other publication. If information about the fisheries licensing policy is not disseminated proactively to fishermen, they may not seek approval to use the safest means available to them to go fishing, thereby increasing the risk to safe fishing operations.

The investigation ascertained that the open boat was not carrying a distress communication device (it was not required to have one on board). Previous TSB investigations have found that carrying an emergency position-indicating radio beacon (EPIRB) can help save lives, and the Board has recommended (TSB Recommendation M00-09) that small fishing vessels carry one or other similar equipment. An EPIRB automatically sends a distress signal once it is immersed in water, so that search and rescue can be initiated immediately.

Loss of life on fishing vessels is a Watchlist issue, and a Safety Issues Investigation into fishing safety was completed in 2012. The Board continues to call for concerted and coordinated action by federal and provincial authorities and by leaders in the fishing community to improve the safety culture in fishing operations.

See the investigation page for more information.

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Richmond, British Columbia, 21 July 2016 – The Transportation Safety Board of Canada (TSB) found that a lack of familiarity with the territory and the misinterpretation of a communication contributed to a Canadian Pacific Railway (CP) train exceeding its limits of authority near Cranbrook, British Columbia, in March 2015, according to its investigation report (R15V0046) released today. No injuries were reported and no dangerous goods were involved.

On 11 March 2015, a CP rail traffic controller stopped a train, consisting of two locomotives and 130 empty cars near Mile 102 on the Cranbrook Subdivision, after the train had departed Cranbrook and travelled east for five miles without authorization. There were no conflicting movements.

The investigation determined that the train had been operated past the east cautionary limits sign at Cranbrook without the required clearance. During the train’s approach to Cranbrook, the train crew had contacted the assistant trainmaster at Fort Steele by radio. The crew members misinterpreted information from the assistant trainmaster, understanding it to be confirmation that the cautionary limits at Cranbrook extended all the way to Fort Steele. As a result, they believed that no additional authority was required and that they could proceed past Cranbrook without requesting a clearance from the rail traffic controller.

These events occurred at about 0120, a time of day that is close to a known circadian rhythm low point when alertness can be compromised. During periods of reduced alertness, there is an increased risk of inadvertent errors such as the misinterpretation of communications.

Although they were qualified for their respective positions, the train crew of three CP management (non-unionized) employees were not familiar with the territory. The investigation identified that if railway management employees who operate trains are not sufficiently familiar with the territory, the limits of operating authority may not be consistently observed, increasing the number of these occurrences and associated risks. It also observed that if the regulations do not adequately address the requirements for training, certification, and territory familiarization for railway management employees who operate trains, trains may be crewed with management employees who are not sufficiently experienced, increasing the risk of unsafe train operations.

Following this occurrence, CP redesignated Cranbrook Yard as a siding. The cautionary limits at the yard were removed, and an adjacent subdivision was combined to operate as one. In addition, CP formalized a requirement for territory familiarization for management crews.

See the investigation page for more information.


The TSB is an independent agency that investigates marine, pipeline, railway and aviation transportation occurrences. Its sole aim is the advancement of transportation safety. It is not the function of the Board to assign fault or determine civil or criminal liability.

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Richmond, British Columbia, 19 July 2016 – In its investigation report (R14V0215) released today, the Transportation Safety Board of Canada (TSB) determined that a seized and locked axle, crew fatigue, and misinterpretation of a fault indicator led to the derailment of a Canadian National Railway (CN) train near Kwinitsa, British Columbia. There were no injuries and no dangerous goods were involved.

On 15 November 2014, a westbound CN train, consisting of 2 locomotives and 153 loaded intermodal flat cars, stopped in a siding to let an oncoming train go by. After exiting the siding, the train seemed to take slightly longer than expected to accelerate. About 12.5 miles west of the siding near Kwinitsa, a surge was felt as the train passed through a switch, and soon after that a train-initiated emergency brake application occurred. After coming to a stop, performing the emergency radio call, and inspecting the train, the crew found that the No. 4 axle of the trailing locomotive was locked and had derailed along with 8 intermodal flat cars consisting of 17 platforms.

The investigation determined that the No. 4 axle of the trailing locomotive had locked when overheating parts on the traction motor assembly cooled down and seized together while the train was stopped in the siding. Extensive wear and heat generation had been occurring within the traction motor assembly due to an undersized traction motor shaft. The locked axle prevented the wheels from rotating and caused the wheels to slide along the rail, become deformed, and then derail as the No. 4 axle passed through the switch near Kwinitsa.

The investigation also found that an intermittent wheel slip indicator had activated when the train resumed its movement and left the siding. These indications are not uncommon when locomotives are pulling with high tractive effort, as they do when accelerating from a stop, and the crew was not concerned by its activation.

The train had passed several wayside inspection systems prior to the derailment without triggering any alarms, including one between the siding and the derailment site. That system however, inspected only 9 axles—even though the train had 424 axles—because the damaged wheel set then dislodged the heat sensors on the inspection system. The scan results for those 9 axles were announced about 30 seconds later. However, the crew did not notice that the announcement had been transmitted much earlier than normal.

The crew members were fatigued at the time of the occurrence, because in the preceding days they had erratic sleep patterns due to work shifts with variable start and end times. Such work/sleep patterns cause circadian rhythm disruptions, which can decrease performance and cognitive function. If shift start times are highly variable, train crew members may not be able to get good quality sleep on a regular basis, increasing the risk of accidents due to fatigue.

Following the occurrence, CN reformatted its wayside inspection systems to include axle counts as part of the post-scan announcement.

See the investigation page for more information.

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Richmond, British Columbia, 14 July 2016 – The Transportation Safety Board of Canada (TSB) today released its investigation report (A14P0132) into the accident in August 2014 in which an Air Tractor AT 802A Fire Boss Amphibian stalled on takeoff and crashed into Chantslar Lake, British Columbia. The pilot received minor injuries and the aircraft was substantially damaged.

On 14 August 2014, the Air Tractor, operating as Tanker 685, was carrying out wildfire management operations during daylight near Chantslar Lake. It was in a group of three similar aircraft working in formation, and was second in line for the touch-and-go runs to scoop water from the lake. On one of Tanker 685’s scooping runs, control was lost during liftoff, and the aircraft’s right wing struck the water. The floats then struck the water and separated from the fuselage as the aircraft yawed 270 degrees to the right. The aircraft remained upright and slowly sank. The pilot exited the cockpit and inflated the personal flotation device being worn. The fourth aircraft jettisoned its load, rejected its takeoff, and taxied to pick up the pilot who had been slightly injured.

The investigation found that a wing stalled, either independently or in combination with an encounter with a wing-tip vortex generated by the lead aircraft. This caused a loss of control moments after liftoff and resulted in both the right-hand wing tip contacting the water and a subsequent water-loop.

The takeoff procedure used, with the aircraft being heavy, its speed below the published power-off stall speed and a high angle-of-attack, contributed to loss of control at an altitude insufficient to permit a recovery.

The investigation also identified that, if takeoff procedures do not specify a liftoff speed, pilots may take advantage of engine power and pitch control capability to get airborne below the published stall speed and risk losing control at an altitude insufficient to permit a recovery. Also, if the aircraft is operated outside of the demonstrated flight envelope, there is a risk pilots will be exposed to aircraft performance for which they are not prepared.

The investigation also found that, even though a safety management system (SMS) and processes were in place, an understaffed management structure during organizational changes likely led to excessive workload for existing managers, and contributed to risks not being addressed through the operator's SMS. Safety management and oversight is an issue on the TSB Watchlist.

After the occurrence and before the 2015 spring training season started, Conair hired a safety manager and a company check pilot for the Fire Boss fleet. Conair also put forward a risk mitigation plan for 2015-16 for the company's AT-802 fleet, which addressed issues found during the investigation.

See the investigation page for more information.

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Dorval, Quebec, 13 July 2016 – The Transportation Safety Board of Canada (TSB) team continues its investigation into the March 2016 collision with terrain of a Mitsubishi MU-2B-60 in Îles-de-la-Madeleine, Quebec.

The occurrence

On 29 March 2016, a private Mitsubishi MU-2B-60 aircraft (United States registration N246W), departed St. Hubert, Quebec, at 0931 local time (Eastern Daylight Time) on a flight to Îles-de-la-Madeleine, Quebec (CYGR). Onboard was the pilot-in-command, a pilot-passenger occupying the right-hand cockpit seat, and 5 passengers.

The autopilot was being used to control the aircraft throughout the flight.

At 1217 Atlantic Daylight Time (ADT), when the aircraft was at approximately 21 000 feet above sea level and 51 nautical miles (nm) from CYGR, the pilot initiated the descent. At 1225, Moncton Area Control Centre cleared the aircraft for an instrument flight rules approach (flying by reference to instruments rather than flying with visual reference to the ground) to CYGR. At 1229, 2.7 nm from Runway 07, the aircraft landing gear was lowered and approach flaps were selected.

Shortly after that, the autopilot was disconnected, and almost immediately the aircraft departed from controlled flight. It rolled quickly into a steep right bank and descended rapidly. The aircraft continued its rapid descent and impacted the ground in a near-level attitude. All 7 occupants were fatally injured.

Investigation teamwork

The Investigator-in-Charge, Mike Cunningham, is being assisted in this investigation by TSB investigators with backgrounds in flight operations, aircraft performance, aircraft systems and engines, human performance, and air traffic control. Representatives from Transport Canada, NAV CANADA, the Sûreté du Québec, the Bureau du coroner du Québec, the National Transportation Safety Board, the Federal Aviation Administration (FAA), the Mitsubishi Aircraft Corporation, Honeywell International Inc., and Hartzell Propeller Inc. are also providing assistance.

Work to date

A site survey was completed and the wreckage was transported to the TSB Engineering Laboratory (Lab) in Ottawa. The field phase of the investigation is complete and the examination and analysis phase is in progress.

TSB investigators have been in contact with the families of the aircraft's occupants to explain the role of the TSB and our investigation process.

A large number of technical and operational documents, weather reports, air traffic control communications, and incident reports have been gathered and reviewed by investigation team members.

Numerous interviews have been conducted with witnesses and individuals from various organizations.

Initial examination and documentation of aircraft systems, components and structural damage has been completed.

What we know

Aircraft

  • The aircraft was certified and equipped to conduct the approved approach into CYGR.
  • The investigation found that both the altitude and the speed of the aircraft's approach to CYGR were higher than recommended.
  • On the MU-2 instrument-approach profile, the standard speed prior to the initial approach fix is 150 knots, slowing to a final approach speed of 125 knots past the final approach fix.
  • In this instance, the aircraft's speed prior to the initial approach fix was 240 knots, and past the final approach fix the speed decreased below 175 knots, only 2.7 nm from Runway 07—much later than prescribed (Figure 1). The aircraft landing gear was lowered and approach flaps were selected at this point.
  • No mechanical deficiencies have been identified with the aircraft's engines, flight controls, landing gear, and navigation systems.
  • Communications with the aircraft throughout the flight were normal.
  • In October 2005, the FAA began a safety evaluation of the MU-2's accident history. As a result, in 2008, it issued a Special Federal Air Regulation (SFAR 108) that requires MU-2 pilots to complete a standardized training program and to use a standardized checklist. At 29 March 2016, this was the third fatal MU-2 accident since SFAR 108's implementation.
  • There are 263 MU-2 aircraft in service; 11 are in Canada.

Lightweight recorder

  • Although not required by regulation, the occurrence aircraft was equipped with a lightweight recording system.
  • It was recovered in good condition from the wreckage.
  • TSB specialists at the Lab have extracted and continue to analyze data from the recorder.
  • The recorder will provide information critical to understanding the circumstances and events that led to the departure from controlled flight—information that would not have been available to the investigation if the aircraft had not been equipped with a recording system.

Aircraft approach path

Figure 1. N246W actual approach (onboard recorder data), compared with the standard aproach
Image of N246W actual approach (onboard recorder data), compared with the standard aproach

Pilot

  • Records indicate the pilot was certified and qualified for the flight in accordance with existing regulations, and had completed the SFAR 108 standardized training program.
  • The pilot had about 2500 hours total flight time, and about 140 hours on the MU-2.

Pilot-passenger

  • The pilot-passenger occupying the right-hand cockpit seat was a commercial pilot and flight instructor.
  • The pilot-passenger was not qualified to fly the MU-2.
  • A second crew member was not required to fly the MU-2.
  • The pilot-passenger was invited to come on the flight to help with some basic piloting functions.

Weather

  • A detailed weather analysis for CYGR on the day of the accident has been completed. Between 0900 and 1500 ADT, visibility varied between 1½ and 3 statute miles. During this same period, ceilings (cloud base heights) varied between 200 and 400 feet above ground level (agl) and northeast winds varied between 20 to 30 knots with gusts as high as 35 knots.
  • Weather forecast for CYGR indicated a potential for moderate mixed icing in cloud, particularly below 10 000 feet in the vicinity of Îles-de-la-Madeleine. There was also the potential for moderate mechanical turbulence below 3000 feet.
  • In accordance with instrument flying rules, the Charlottetown airport (CYYG) had been selected as the alternate airport.

Next steps

The next steps of the investigation include the following work:

  • Analyzing the accident flight profile to understand the approach phase of the flight and the challenges encountered by the pilot.
  • Evaluating aircraft performance and determining if weather affected the performance.
  • Evaluating pilot training and experience, and human performance aspects.
  • Reviewing MU-2B aircraft handling and approach-and-landing issues.
  • Evaluating the SFAR 108 standardized training, and other MU-2 safety action taken in the past.
  • Conducting additional interviews as required.
  • Completing the report phase of the investigation.

Outstanding safety issues

Approach-and-landing accidents

Every year, millions of successful landings occur on Canadian runways. However, there is a risk that accidents resulting in loss of life, injury, and aircraft damage can occur during the approach-and-landing phase of flight. In Canada, from 2009 to 2013, Canadian-registered aircraft were involved in an average of 150 approach-and-landing accidents every year. The TSB Watchlist identifies approach-and-landing accidents as one issue which poses the greatest risk to Canada's transportation system.

Stable approaches significantly increase the chances of a safe landing. Without improvements to stable-approach policy compliance, most unstable approaches will continue to a landing, increasing the risk of approach-and-landing accidents.

Lightweight flight recording systems

In 2013, following its investigation into the March 2011 loss of control/in-flight break-up occurrence, northeast of Mayo, Yukon (TSB Aviation Investigation Report A11W0048), the TSB found that if cockpit or data recordings are not available to an investigation, the identification and communication of safety deficiencies to advance transportation safety may be precluded. It further concluded that in the event that an accident does occur, recordings from lightweight flight recording systems will provide useful information to enhance the identification of safety deficiencies in the investigation. Therefore, the Board recommended that

The Department of Transport work with industry to remove obstacles to and develop recommended practices for the implementation of flight data monitoring and the installation of lightweight flight recording systems by commercial operators not currently required to carry these systems.
TSB Recommendation A13-01

TSB Recommendation A13-01 speaks about the benefits of lightweight flight recording systems for smaller commercial operations. However, this kind of system would also be equally beneficial for aircraft operated by private operators, for flight training and general aviation aircraft as demonstrated in this occurrence. As noted, in this investigation, valuable information was extracted and is being analyzed.

Communication of safety deficiencies

Should the investigation team uncover a safety deficiency that represents an immediate risk to aviation, the Board will communicate immediately so that it may be addressed quickly and the aviation system made safer.

The information posted is factual in nature and does not contain any analysis. Analysis of the accident and the Findings of the Board will be part of the final report.

The investigation is ongoing.

Visit the active investigation page for more information about this investigation.

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Richmond Hill, Ontario, 06 July 2016 – Today, the Transportation Safety Board of Canada (TSB) released its investigation report (A14O0165) into the loss of control occurrence near London, Ontario, involving an ExpressJet Airlines flight. There were no reported injuries to the 3 crew members or 26 passengers, and the aircraft was not damaged.

On 5 September 2014, an Embraer 145LR departed Grand Rapids, Michigan, destined for Newark Liberty International Airport, New Jersey. After departure, the aircraft deviated north of its intended track into Canadian airspace to avoid a line of thunderstorms, and climbed to its cruising altitude with the intention of navigating its way through them. The aircraft flew through a large thunderstorm that it could not avoid and encountered severe turbulence. The flight crew lost control of the aircraft and it descended rapidly, losing approximately 4000 feet, before they were able to regain control. The aircraft continued to its destination, where it landed safely.

The TSB investigation found that the flight crew anticipated that they would be able to navigate between thunderstorms. However, as the flight progressed, the line of thunderstorms intensified, and the intended route became obstructed. As well, the report observed that, during the loss of control, the flight crew momentarily applied flight control inputs that exacerbated the roll attitude of the aircraft. As a result, recovery time and altitude loss were increased. The investigation further found that when flight crews operate an aircraft outside of manufacturer recommendations and its limitations, there is a risk of compromising flight safety, resulting in injury to the occupants or damage to the aircraft.

Following this occurrence, ExpressJet Airlines improved dispatcher use of flight-following software, and developed policy and procedures related to adverse weather phenomena. ExpressJet Airlines also developed a training module for all flight crew members to promote severe weather avoidance and weather radar utilization techniques to identify developing storm activity.

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Dorval, Quebec, 05 July 2016 – In its investigation report (A14Q0068) released today, the Transportation Safety Board of Canada (TSB) found that the failure of an engine oil feed tube seal led to the turbine rotor failure, and a subsequent fire, during Bombardier engine ground tests at the Montréal International (Mirabel) Airport, Quebec.

On 29 May 2014, two pilots and four test engineers onboard a Bombardier CS100 were conducting engine ground runs at the Mirabel Airport; this was part of testing processes prior to aircraft certification by Transport Canada. During the test, the left engine, manufactured by Pratt & Whitney Canada, experienced an uncontained turbine rotor failure and sudden power loss. The crew immediately shut down the engine and declared an emergency after being advised of smoke and fire on the engine. All personnel on board evacuated the aircraft safely, but the engine and aircraft sustained substantial damage.

The investigation determined that “heat soaking,” as a result of insufficient cooldown, caused the seal of a bearing oil feed tube to fail. It was determined that the engine had been shut down after high power operation, without sufficient time for its internal temperatures to reduce at lower power. As a result, when the seal failed, it allowed engine oil to mix with the turbine rotor's cooling air flow. The resulting air/oil mixture ignited due to high ambient temperatures, and the ensuing combustion caused the entire turbine rotor stage to fail. This resulted in major damage to the engine, nacelle and wing.

The investigation identified that Pratt & Whitney had issued a Restriction and/or Special Instruction (RSI) with cooling procedures for their engines before shutdown, with alternate solutions for hot shutdowns. Bombardier interpreted the alternate solutions in the RSI as an alternative equal to the other shutdown options contained in the RSI. This resulted in the engine being exposed to one or more hot shutdowns, which led to heat soaking beyond the design criteria of the bearing oil feed tube's seal.

The investigation also found that, while Bombardier ground personnel successfully extinguished the fire, the engine's fire extinguishing system had not been activated. There is an increased risk that fire may spread if nacelle fire bottles are not deployed in the event of a fire, and/or if ground fire extinguishers are not located in a way to permit quick access.

Following the occurrence, Bombardier grounded the C Series test aircraft fleet until the cause of the occurrence could be clearly established. For its part, Pratt & Whitney proposed a plan to return to flight which included an enhanced seal, a revised cool-down procedure, and other measures to monitor engine temperatures and prevent hot shutdowns. Further, production engines will feature an enhanced oil supply tube and a cooling airflow configuration that will physically separate the turbine rotor airflow from the bearing compartment to eliminate the possibility of recurrence.

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