Geographical / Geophysical / Scientific

The pilot’s failure to maintain adequate airspeed, which caused the airplane to exceed its critical angle of attack and enter an inadvertent stall and spin.

Findings as to causes and contributing factors:
1. The pilot did not continuously use oxygen above 13 000 feet and likely became hypoxic as the aircraft climbed to 15 000 feet. The pilot did not recognize his symptoms or take action to restore his supply of oxygen.
2. As a result of hypoxia-related cognitive and perceptual degradations, the pilot was unable to maintain effective control of the aircraft or to respond appropriately to the asymmetric power condition.
3. The aircraft departed controlled flight and entered a spin to the right because the airspeed was below both the published minimum control speed in the air and the stall speed, and because there was a significant power asymmetry, a high angle of attack, and significant asymmetric drag from the windmilling propeller of the right engine.
4. When the aircraft exited cloud, the pilot completed only 1 of the 7 spin-recovery steps: reducing the power to idle. As the aircraft continued to descend, the pilot took no further recovery action, except to respond to air traffic control and inform the controller that there was an emergency.

Findings as to risk:
1. If flight crews do not undergo practical hypoxia training, there is a risk that they will not recognize the onset of hypoxia when flying above 13 000 feet without continuous use of supplemental oxygen.

Other findings:
1. The weather information collected during the investigation identified that the loss of control was not due to in-flight icing, thunderstorms, or turbulence.
2. Because the Appareo camera had been bumped and its position changed, the pilot’s actions on the power controls could not be determined. Therefore, the investigation was unable to determine whether the power asymmetry was the result of power-quadrant manipulation by the pilot or of an aircraft system malfunction.
3. The flight path data, audio files, and image files retrieved from the Appareo system enabled the investigators to better understand the underlying factors that contributed to the accident.

Findings:
Findings as to causes and contributing factors:
- Sensation seeking, mental fatigue, and an altered risk perception very likely contributed to the fact that, immediately after completing the magnetometric survey work, the pilot flying descended to an altitude varying between 100 and 40 feet above ground level and maintained this altitude until the aircraft collided with the wires.
- It is highly likely that the pilots were unaware that there was a power transmission line in their path.
- The pilot flying did not detect the power transmission line in time to avoid it, and the aircraft collided with the wires, which were 70 feet above the ground.
- Despite the warning regarding low-altitude flying in the Transport Canada Aeronautical Information Manua, and in the absence of minimum-altitude restrictions imposed by the company, the pilot chose to descend to a very low altitude on the return flight; as a result, this flight segment carried an unacceptable level of risk.

Findings as to risk:
- If pilots fly at low altitude, there is a risk that they will collide with wires, given that these are extremely difficult to see in flight.
- If lightweight flight data recording systems are not used to closely monitor flight operations, there is a risk that pilots will deviate from established procedures and limits, thereby reducing safety margins.
- If Transport Canada does not take concrete measures to facilitate the use of lightweight flight data recording systems and flight data monitoring, there is a risk that operators will be unable to proactively identify safety deficiencies before they cause an accident.
- If safety management systems are not required, assessed, and monitored by Transport Canada in order to ensure continual improvement, there is an increased risk that companies will be unable to effectively identify and mitigate the hazards involved in their operations.
- Not wearing a safety belt increases the risk of injury or death in an accident.
- The current emergency locator transmitter system design standards do not include a requirement for a crashworthy antenna system. As a result, there is a risk that potentially life-saving search‑and‑rescue services will be delayed if an emergency locator transmitter antenna is damaged during an occurrence.

The following factors were identified:
- Controlled flight into terrain,
- Execution of a VFR flight in reduced visibility weather conditions,
- Poor decision making by the crew in continuing VFR operation as they were in an environment of significantly reduced visibility,
- Inadequate operational risk assessment due to the lack of familiarity of the foreign crew with the topography and meteorological evolution of the sector.

Controlled flight into terrain after the pilot was flying under VFR mode in IMC conditions. It was determined that the accident occurred after the pilot suffered a loss of situational awareness while flying under VFR mode in low clouds conditions.

There was sufficient fuel in the tanks at the time of the accident as the aircraft was refueled prior to departure for a 5-hour flight. The exact cause of the double engine failure remains unknown. When the right engine failed, the pilot was flying at an altitude of 330 feet which was below the minimum safe altitude fixed at 500 feet. Also, he was apparently using his cell phone.

Conclusions
Findings as to Causes and Contributing Factors:
1. The right engine lost power when the intermediate spur gear on the torque sensor shaft failed. This resulted in loss of drive to the high-pressure engine-driven pump, fuel starvation, and immediate engine stoppage.
2. The ability of the left-hand No. 2 ejector pump to deliver fuel to the collector tank was compromised by foreign object debris (FOD) in the ejector pump nozzle.
3. When the fuel level in the left collector tank decreased, the left fuel level warning light likely illuminated but was not noticed by the crew.
4. The pilots did not execute the fuel level warning checklist because they did not perceive the illumination of the fuel level left tank warning light. Consequently, the fuel crossfeed valve remained closed and fuel from only the left wing was being supplied to the left engine.
5. The left engine flamed out as a result of depletion of the collector tank and fuel starvation, and the crew had to make a forced landing resulting in an impact with a concrete noise abatement wall.
Findings as to Risk:
1. Depending on the combination of fuel level and bank angle in single-engine uncoordinated flight, the ejector pump system may not have the delivery capacity, when the No. 1 ejector inlet is exposed, to prevent eventual depletion of the collector tank when the engine is operated at full power. Depletion of the collector tank will result in engine power loss.
2. The master caution annunciator does not flash; this leads to a risk that the the crew may not notice the illumination of an annunciator panel segment, in turn increasing the risk of them not taking action to correct the condition which activated the master caution.
3. When cockpit voice and flight data recordings are not available to an investigation, this may preclude the identification and communication of safety deficiencies to advance transportation safety.
4. Because the inlets of the ejector pumps are unscreened, there is a risk that FOD in the fuel tank may become lodged in an ejector nozzle and result in a decrease in the fuel delivery rate to the collector tank.
Other Findings:
1. The crew’s decision not to recover or jettison the birds immediately resulted in operation for an extended period with minimal climb performance.
2. The composition and origin of the FOD, as well as how or when it had been introduced into the fuel tank, could not be determined.
3. The SkyTrac system provided timely position information that would have assisted search and rescue personnel if position data had been required.
4. Saskatoon police, firefighters, and paramedics responded rapidly to the accident and provided effective assistance to the survivors.

Landing gear went through the ice after landing on ice/snow terrain.