Background
On December 11, 2015, the pilot of Wasaya Airways flight 127 (WSG127) reported for duty at the company hangar at Pickle Lake Airport (CYPL), Ontario, at approximately 0815. The flight was the first of three planned cargo trips in a Cessna 208B Caravan (registration C-FKDL, serial number 208B0240) from CYPL to Angling Lake/Wapekeka Airport (CKB6), Ontario. The pilot conducted a pre-flight inspection while ground crew loaded cargo. A fuel-handling technician confirmed with the pilot a planned fuel load of 600 pounds per wing of Jet A fuel, and verified the distribution using cockpit fuel-quantity indicators. The pilot then received a briefing from the station manager, was informed that the first officer had been reassigned to increase payload for a snowmobile, and completed a flight dispatch clearance (FDC) form for WSG127. The FDC indicated the flight would be conducted under visual flight rules, with company flight-following, at an altitude of 5500 feet above sea level, with an en route time of 66 minutes and fuel consumption of 413 pounds.
Flight Sequence
The pilot returned to the aircraft, conducted a final walk-around and upper wing inspection, started the engine at 0854, and performed ground checks. At 0858, the pilot advised on the mandatory frequency (122.2 MHz) that WSG127 was taxiing for departure from Runway 09. The aircraft departed at 0900 and reported airborne at 0901. The flight climbed eastward, turned left toward the track to CKB6, briefly descended about 100 feet over 10 seconds around 3000 feet ASL, then resumed climbing. At 0905, the pilot reported clear of the mandatory frequency zone. WSG127 intercepted the track and climbed northward, reaching a peak altitude of about 4600 feet ASL at 0908:41. At 0908:46, the flight began descending. At 0909:16, the aircraft made a sharp right turn of about 120° while descending through approximately 4000 feet ASL. The descent ended at about 2800 feet at 0909:39, followed by a climb to about 3000 feet before descending again. At approximately 0910, during daylight hours, WSG127 collided with trees and terrain at an elevation of 1460 feet ASL.
Investigation Findings
The official investigation identified several findings as to causes and contributing factors. Although the Cessna 208B was prohibited from flying in known or forecast icing conditions, WSG127 was dispatched into forecast icing conditions. The high take-off weight increased the severity of degraded performance when icing was encountered. The pilot continued the flight in icing conditions for about 6 minutes, leading to progressively degraded performance. Substantial ice accumulation resulted in an aerodynamic stall, loss of control, and collision with terrain. The Type C pilot self-dispatch procedures and practices at Wasaya did not ensure operational risk management to an acceptable level. Wasaya had not fully implemented mitigation strategies from its January 2015 risk assessment of Cessna 208B operations in known or forecast icing, leaving the company exposed to unmitigated hazards. There was a company norm of dispatching Cessna 208B flights into forecast icing despite four of the five such aircraft being prohibited from operating in those conditions.
Additional findings as to risk were noted, including the lack of effective risk-management processes, inadequate tools for pilot self-dispatch risk assessments, dispatching aircraft not certified for icing into such conditions, dispatching certified aircraft at weights exceeding limitations, continuing flights in known icing, exceeding manufacturer-recommended de-icing boot servicing intervals, insufficient pilot training, inaccurate center-of-gravity calculations, and fragile emergency locator transmitter antennas. Other findings noted that Wasaya's satellite flight-following system provided early warning and an accurate last known position for search-and-rescue, and that the investigation could not determine whether the autopilot was used.
Probable Cause
The probable cause, as stated in the official findings, includes: the aircraft was dispatched into forecast icing conditions although prohibited; high take-off weight increased severity of degraded performance; the pilot continued flight in icing for about 6 minutes; ice accumulation led to aerodynamic stall, loss of control, and collision with terrain; Wasaya's self-dispatch procedures did not ensure acceptable risk management; mitigation strategies from a risk assessment were not fully implemented; and there was a company norm of dispatching Cessna 208B flights into forecast icing.