The three indicators were:
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PROP LOW P: an indication that the propeller had reached its minimum pitch in flight.
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CHIP: a warning that metal particles had been detected in the turboprop engine oil.
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F-FILTER: an alert indicating that the fuel filter was clogged.
These findings are potentially important because they involve the propeller, engine lubrication, and fuel supply.
However, the report also makes an essential qualification: investigators had not yet determined whether the indicators illuminated before or after the loss of control.
That timing matters enormously.
If a warning appeared before the aircraft began losing control, it might provide evidence of a developing technical problem. If it appeared only after the aircraft had already entered an abnormal flight condition or during the impact sequence, its significance could be different.
The warning lights therefore represent clues, not a final explanation.
What the CHIP warning could mean
The CHIP warning is associated with the detection of metal particles in the engine oil.
Metal particles may be produced by wear or damage inside mechanical components. In an engine, the presence of metal contamination can indicate that parts are rubbing, deteriorating, or failing.
But the indicator alone cannot identify which component was involved, how serious the issue was, or when the contamination began.
Investigators would need to examine the oil system, engine components, filters, and any recovered material. They would also need to compare physical findings with the recorded engine data.
The preliminary report does not conclude that the CHIP warning caused the accident.
What the F-FILTER alert could mean
The F-FILTER alert indicates a clogged fuel filter.
A fuel filter is designed to prevent contamination from reaching the engine's fuel system. If a filter becomes obstructed, the flow of fuel may be affected.
A fuel-flow problem could potentially influence engine performance. That makes the warning relevant when investigators are examining the sudden reduction in Ng.
But the presence of the warning lamp does not prove that the fuel filter caused the reduction in engine speed.
The BEA was still examining the fuel system and awaiting laboratory analysis of a fuel sample collected from the aircraft.
The report also notes that the fuel supplier had arranged independent analyses of samples from the airport's tanker and storage tank. Those analyses did not reveal an abnormality.
The investigators therefore had several separate questions to answer: whether the aircraft's fuel system was functioning properly, whether a filter restriction occurred, and whether any such problem could explain the engine's recorded behavior.
The PROP LOW P warning
The PROP LOW P warning indicates that the propeller has reached a minimum pitch in flight.
The propeller's pitch determines the angle of its blades as they move through the air. A variable-pitch propeller adjusts this angle to help the engine operate efficiently under different flight conditions.
An abnormal indication involving propeller pitch could be relevant to a sudden change in aircraft performance.
However, the preliminary report does not establish when the warning appeared or what caused it.
It is therefore too early to conclude that a propeller malfunction was responsible for the crash.
The fuel system examination
The aircraft's fuel system had been heavily damaged in the crash, but investigators were able to reconstruct parts of it for examination.
Fuel was found in the system during dismantling. The left fuel tank provided a sample for laboratory testing, while the right tank had been ruptured and contained only a very small amount of remaining fuel.
The aircraft had received approximately 200 litres of fuel after the first block of three rotations, two flights before the accident flight. The BEA estimated that around 200 litres were present at take-off on the fatal flight.
These details are important because the investigation must consider whether a fuel-supply problem could explain the reduction in engine performance.
The report does not identify fuel contamination as the cause. The independent tests of fuel from the airport supply did not reveal an abnormality, while further analysis of the aircraft's own fuel system was continuing.
The search for the source of smoke
The investigators also carried out a systematic search for physical evidence that smoke had been present inside the aircraft.
They examined the wreckage for soot, unusual heating, damage to insulation, and other signs that might indicate a fire or overheating.
The electrical system was separated from the aircraft structure and examined. The BEA did not identify signs of overheating, damaged insulation, or another anomaly that could have generated smoke.
The air-conditioning system was also removed for examination. Investigators did not find areas of overheating or soot deposits that would confirm smoke in that system.
These findings are important because they make some possible explanations less obvious.
But the absence of soot or visible smoke in the examined material does not automatically explain why two instructors reported seeing smoke.
The investigators still need to determine whether the reported phenomenon came from a system that left little physical evidence, whether it was a visual misinterpretation, or whether another explanation is possible.
Flames seen after the impact
A witness who was driving nearby saw the aircraft take off and then lose control.
After the crash, the witness immediately went to the site and noticed flames near the front-left section of the aircraft, approximately 30 to 40 centimetres behind the propeller.
The witness used a dry-powder extinguisher carried in the vehicle and quickly extinguished the flames. Approximately half of a two-kilogram extinguisher was used.
The BEA stated that further examinations were required to determine whether this fire was a consequence of the impact or whether it had another origin.
That distinction is crucial.
A fire after impact does not prove that a fire was present before impact. The collision could have damaged fuel or other systems and created a fire at the scene.
On the other hand, if investigators can establish that a fire existed before the crash, it could help explain the smoke warnings and the emergency sequence.
The available preliminary findings do not settle that question.
Chapter 5: What Investigators Still Need to Discover
The preliminary report has reconstructed the flight in considerable detail, but it is not the final investigation report.
That distinction is essential. The document was published to provide an initial account of the evidence collected so far, not to assign blame or announce a definitive cause.
The BEA's stated purpose is to improve aviation safety. Its investigation is intended to establish the circumstances of the accident and identify lessons that may help prevent similar events, rather than determine legal responsibility.
Several major areas of work remained open when the preliminary report was published.
The engine must be examined in detail
The turboprop engine was one of the most important subjects for further investigation.
The BEA planned to examine it at Pratt & Whitney's facilities in Canada, with the French investigators present.
This examination could help determine whether the engine experienced an internal mechanical problem, whether a component failed, and whether the observed reduction in gas-generator speed was associated with a specific technical defect.
The investigators will need to compare the physical condition of the engine with the recorded flight parameters.
For example, if a mechanical failure is identified, they will need to determine whether it could explain the timing and magnitude of the Ng reduction. They will also need to assess whether it could have generated smoke or another visible sign inside the cabin.
A finding involving the engine could provide an important link between the first warnings and the aircraft's deteriorating performance.
But until those examinations are complete, it would be premature to identify a specific engine component as the cause.
The fuel system remains an important line of investigation
The fuel system is another area that requires careful examination.
The preliminary report describes the aircraft's fuel configuration, the amount of fuel on board, the fuel added between groups of flights, and the physical condition of the recovered components.
Investigators also found that the warning panel likely showed an F-FILTER alert at impact, although its activation time remains uncertain.
The fuel sample collected from the aircraft must be analyzed, and the reconstructed fuel system must be examined to determine whether a restriction, leak, or other abnormality could have affected engine operation.
The fact that independent samples from the airport's fuel supply did not show an abnormality is useful, but it does not eliminate every possible problem within the aircraft's own fuel system.
What caused the smoke warning?
Perhaps the most difficult unanswered question is still the one that began the emergency.
Two instructors reported smoke in the forward-right area of the cabin. Yet the five GoPro recordings and the available external videos did not show visible smoke.
The electrical and air-conditioning examinations also did not reveal clear signs of overheating or soot.
This leaves several possibilities open.
The instructors may have seen a small amount of smoke that the cameras could not capture. They may have noticed vapor, dust, or another visual phenomenon that resembled smoke. Alternatively, an issue may have occurred in a part of the aircraft that did not leave obvious traces in the recovered components.