History
At 1503 Central Standard Time, a Construcciones Aeronauticas SA (CASA) C-212-CC40 (registration C-FDKM, serial number 196) operated by Fugro Aviation Canada Ltd. departed Saskatoon/Diefenbaker International Airport, Saskatchewan, on a visual flight rules geophysical survey flight east of Saskatoon. On board were 2 pilots and a survey equipment operator. The aircraft had conducted a normal survey flight earlier that day. After that flight, an aircraft maintenance engineer fuelled the aircraft with 1703 litres of Jet A fuel. Before the occurrence flight, the pilots performed a pre-flight inspection, confirming operational annunciator panel lights, single red line and torque/temperature limiting systems. The aircraft weight and balance were calculated using a spreadsheet. The captain occupied the left seat and the first officer the right seat. Fuel totalizers were reset to zero, and both engine starts were normal.
The survey area was within 30 nautical miles east of Saskatoon over flat terrain at 1700–1800 feet asl. Initial calibration was at 5500 feet asl, then descent to 400 feet agl for survey. The aircraft had no autopilot; the pilot flying maintained altitude by visual reference and radar altimeter. The first 3 hours were normal, with control transfers hourly. At the time of the occurrence, the first officer was flying northbound on the last line of the survey block, with about 10 nautical miles remaining. The aircraft was straight and level, flaps up, with two survey sensors (birds) deployed. Altitude was 2300 feet asl, indicated airspeed 130 knots, engine power stable at 99.7% rpm and 60–65% torque. Both fuel booster pumps were on, crossfeed closed, fuel pressure normal. No annunciators or warning lights were illuminated. Fuel flow was 340 pph left engine and 360 pph right engine.
Right Engine Power Loss
At about 1814, the right engine lost power. The investigation found that the case hardening of gear tooth flanks and roots of two spur gears in the torque sensor gear train was below manufacturer specifications, likely leading to wear. Combined wear of the two gears likely caused abnormal vibration, leading to fatigue cracking in the tooth roots of the intermediate gear. The intermediate spur gear subsequently separated into fragments, causing loss of power transmission to the high-pressure engine-driven fuel pump, resulting in fuel starvation, flameout, and power loss. The shudder felt was almost certainly associated with the gear failure. The engine-driven fuel pump was no longer operating, so restart attempts would have been unsuccessful.
The right engine chip plug did not initially display electrical continuity, so the chip warning light did not illuminate. Metal chips observed on the plug likely fell onto it during wreckage recovery.
One-Engine Inoperative Performance and Bird Recovery
After the right engine power loss, the aircraft was flown with an average 5° left bank, with variability. Climb performance was marginal. Both birds remained deployed for 3–4 minutes after the power loss because pilots were initially uncertain about maintaining altitude, and recovering or jettisoning birds required the survey equipment operator to leave his seat. This high-drag configuration reduced climb performance. The terrain was flat, so this did not pose a hazard.
Left Engine Power Loss
When the flight was 3.5 nautical miles from Runway 27 on final approach, the left engine lost power. The fuel system analysis showed that with the right engine inoperative and uncoordinated flight, usable fuel in the left wing was about 656 pounds. At bank angles exceeding 5.8°, the No. 1 ejector pump inlet would be exposed, leaving only the No. 2 ejector pump to transfer fuel to the collector tank. Foreign object debris (FOD) was found in the No. 2 ejector pump nozzle. Testing demonstrated that with FOD present, the collector tank could supply fuel for approximately 13:21 to 16:03 minutes. The time between right and left engine power losses was 14:05 minutes. The FOD material was dissimilar to sealant used in fuel tank construction, but its origin and introduction method could not be determined. The staining of the No. 2 ejector pump nozzle indicated it had been present for some time. The booster pump check valve fittings were not completely tight, and a small hole was chafed in the No. 2 ejector pump delivery pipe, but these defects did not appreciably diminish fuel supply.
The low fuel level warning system likely functioned normally. The left low fuel level and master caution lamps likely illuminated about 3–4 minutes after the right engine power loss.
Forced Landing
The crew carried out a forced landing adjacent to Wanuskewin Road in Saskatoon. The aircraft impacted a concrete roadway noise abatement wall and was destroyed. The survey equipment operator sustained fatal injuries, the first officer sustained serious injuries, and the captain sustained minor injuries. No ELT signal was received.
Findings
The right engine lost power when the intermediate spur gear on the torque sensor shaft failed, resulting in loss of drive to the high-pressure engine-driven fuel pump. The left engine lost power due to fuel starvation caused by foreign object debris in the No. 2 ejector pump, compounded by uncoordinated flight after the right engine failure.