British Columbia

Findings as to Causes and Contributing Factors:
1. The take-off was attempted at an aircraft weight that did not meet the performance capabilities of the aircraft to clear an obstacle and, as a result, the aircraft struck a telephone pole and a telephone cable during the initial climb.
2. A take-off and climb to 50 feet performance calculation was not completed prior to take-off; therefore, the flight crew was unaware of the distance required to clear the telephone cable.
3. The southeast end of the airstrip was not clearly marked; as a result, the take-off was initiated with approximately 86 feet of usable airstrip behind the aircraft.
4. The take-off was attempted in an upslope direction and in light tailwind, both of which increased the distance necessary to clear the existing obstacles.
Findings as to Risk:
1. Operational control within the company was insufficient to reduce the risks associated with take-offs from the lodge airstrip.
2. The take-off weight limits for lodge airstrip operations were not effectively communicated to the flight crew.
3. Maximum performance short take-off and landing (MPS) techniques may have been necessary in order to accomplish higher weight Twin Otter take-offs from the lodge airstrip; however, neither the aircraft nor the company were approved for MPS operations.
4. The first officer’s shoulder harness assembly had been weakened by age and ultraviolet (UV) light exposure; as a result, it failed within the design limits at impact.
5. The SeeGeeTM calculator operating index (OI) values being used by Liard Air Twin Otter pilots was between 0.5 and 1.0 units greater than the correct SeeGeeTM OI values; therefore, whenever the SeeGeeTM calculator was used for flight planning, the actual centre of gravity (c of g) of the aircraft would have been forward of the calculated CofG.
6. There are no airworthiness standards specifically intended to contain fuel and/or to prevent fuel ignition in crash conditions in fixed-gear United States Civil Aviation Regulation 3 and United States Federal Aviation Regulation 23 aircraft.

Findings as to Causes and Contributing Factors:
1. A late full flap selection at 300 feet above ground level (agl) likely destabilized the aircraft’s pitch attitude, descent rate and speed in the critical final stage of the precision approach, resulting in an increased descent rate before reaching the runway threshold.
2. After the approach lights were sighted at low altitude, both pilots discontinued monitoring of instruments including the glide slope indicator. A significant deviation below the optimum glide slope in low visibility went unnoticed by the crew until the aircraft descended into the approach lights.
Finding as to Risk:
1. The crew rounded the decision height (DH) figure for the instrument landing system (ILS) approach downward, and did not apply a cold temperature correction factor. The combined error could have resulted in a descent of 74 feet below the DH on an ILS approach to minimums, with a risk of undershoot.
Other Finding:
1. The cockpit voice recorder (CVR) was returned to service following an intelligibility test that indicated that the first officer’s hot boom microphone intercom channel did not record. Although the first officer voice was recorded by other means, a potential existed for loss of information, which was key to the investigation.

Findings as to Causes and Contributing Factors:
1. The pilot entered the valley at an altitude above ground that did not provide sufficient terrain clearance given the aircraft’s performance.
2. The pilot encountered steeply rising terrain, where false horizon and relative scale illusions in the climb are likely. Realizing that the aircraft would not likely be able to out-climb the approaching terrain, he turned to reverse his course.
3. The aircraft’s configuration, relatively high weight, combined with the effects of increased drag from the equipment, density altitude, down-flowing winds, and manoeuvring resulted in the aircraft colliding with terrain during the turn.
Findings as to Risk:
1. A detailed flight plan was not filed and special equipment, such as laser radiation emitting devices and/or hazardous substances were not reported. The absence of flight plan information regarding these devices could delay search and rescue efforts and expose first responders to unknown risks.
2. Transport Canada (TC) does not issue a rating/endorsement for mountain flying training. There are no standards established to ascertain the proficiency of a pilot in this environment. Pilots who complete a mountain flying course may not acquire the required skill sets.
3. There was no emergency locator transmitter (ELT) signal received. The ELT was destroyed in the impact and subsequent fire. Present standards do not require that ELTs resist crash damage.
4. “Flight permits – specific purpose” are issued for aircraft that do not perform as per the original type design but are deemed capable of safe flight. Placards are not required; therefore, pilots and observers approved to board may be unaware of the limitations of the aircraft and the associated risks.
5. The TC approval process allowed the continued operation of this modified aircraft for sustained environmental research missions under a flight permit authority. This circumvented the requirement to meet the latest airworthiness standards and removed the risk mitigation built into the approval process for a modification to a type design.
Other Findings:
1. The fuel system obstruction found during disassembly was a result of the post-crash fire.
2. The aircraft was operated at an increased weight allowance proposed by the design approval representative (DAR). Such operation was to be approved only in accordance with a suitably worded flight permit and instructions contained in the proposed document CN-MSC-011; however, this increased weight allowance was not incorporated to any flight authority issued by TC.

Findings as to Causes and Contributing Factors:
1. The downwind condition on approach contributed to the aircraft landing long and with a high ground speed. This, in combination with hydroplaning, prevented the crew from stopping the aircraft in the runway length remaining.
2. When the decision to abort the landing was made, there was insufficient distance remaining for the aircraft to accelerate to a sufficient airspeed to lift off.
3. The overrun area for Runway 09 complied with regulatory standards, but the obstacles and terrain contour beyond the overrun area contributed to the fatality, the severity of injuries, and damage to the aircraft.
Finding as to Risk:
1. Alert Service Bulletin A25-1124A (dated 01 June 2000), which recommended replacing the inertia reel aluminum shaft with a steel shaft, was not completed, thus resulting in the risk of failure increasing over time.
Other Findings:
1. The weather station at the Powell River Airport does not have any air–ground communication capability with which to pass the flight crew timely wind updates.
2. The decision to make a second approach was consistent with normal industry practice, in that the crew could continue with the intent to land while maintaining the option to break off the approach if they assessed that the conditions were becoming unsafe.

Findings as to Causes and Contributing Factors:
1. The engine lost power when a compressor turbine blade failed as a result of the overstress extension of a fatigue-generated crack. The fracture initiated at a metallurgical anomaly in the parent blade material and progressed, eventually resulting in blade failure due to overstress rupture.
2. The combination of aircraft position at the time of the engine failure, the lack of equipment enabling the pilot to locate and identify high terrain, and the resultant manoeuvring required to avoid entering instrument flight conditions likely prevented the pilot from attempting to glide to the nearest airfield.
Findings as to Risk:
1. Single-engine instrument flight rules (SEIFR) operations in designated mountainous regions have unique obstacle risks in the event of an engine failure. Canadian equipment requirements for such operations do not currently include independent terrain mapping, such as terrain awareness and warning systems (TAWS).
2. Airline operators are not currently required to conduct any additional route evaluation or structuring to ensure that the risk of an off-field landing is minimized during SEIFR operations.
3. Pilots involved in commercial SEIFR operations do not receive training in how to conduct a forced landing under instrument flight conditions; such training would likely improve a pilotís ability to respond to an engine failure when operating in instrument meteorological conditions (IMC).
4. Mean time between failure (MTBF) calculations do not take into account In Flight Shut Downs (IFSDs) not directly attributable to the engine itself; it may be more appropriate to monitor all IFSD events.
5. The design of the Cessna 208B Caravan fuel shutoff valves increases the risk that the valves will open on impact, allowing fuel spillage and increasing the potential for fire.
Other Finding:
1. Sonicblue Airways was not providing downloaded engine parameter data for engine condition trend monitoring (ECTM) evaluation at appropriate intervals.

Findings as to Causes and Contributing Factors:
1. During the take-off, the left engine combustion chamber plenum split open due to a fatigue crack. The rupture was so extensive that the engine flamed out.
2. The crew did not feather the left engine or retract the flaps, and the aircraft entered a moderate left-hand turn after take-off; the resulting drag caused the aircraft to descend until it contacted trees.
3. The first officer’s flying skills may have been challenged during the handling of the engine failure, and the checklist was conducted out of sequence, suggesting that there may have been uncertainty in the cockpit. A contributing factor may have been the captain’s unfamiliarity with handling an emergency from the right seat.
4. The use of flap 20 for take-off, although in accordance with company policy, contributed to the difficulty in handling the aircraft during the emergency.
Findings as to Risk:
1. The TPE331 series engine plenum is prone to developing cracks at bosses, particularly in areas where two bosses are in close proximity and a reinforcing weld has been made. Cracks that develop in this area cannot necessarily be detected by visual inspections or even by fluorescent dye-penetrant inspections (FPIs).
2. Because the wing was wet and the air temperature was at 0°C, it is possible that ice may have formed on top of the wing during the take-off, degrading the wing’s ability to generate lift.
3. Being required to conduct only flap 20 take-offs increases the risk of an accident in the event of an engine problem immediately after take-off.
Other Finding:
1. The plenum manufactured with a single machined casting, incorporating the P3 and bleed air bosses, is an improvement over the non-single casting boss plenum; however, cracks may still develop at bosses elsewhere on the plenum.