ASN Wikibase Occurrence # 319781
| Date: | Thursday 2 November 2017 |
| Time: | 19:21 |
| Type: |  Fairchild SA227-AC Metro III |
| Owner/operator: | Perimeter Aviation |
| Registration: | C-FLRY |
| MSN: | AC-756B |
| Year of manufacture: | 1990 |
| Total airframe hrs: | 24672 hours |
| Engine model: | Garrett TPE331-11U-612G |
| Fatalities: | Fatalities: 0 / Occupants: 2 |
| Aircraft damage: | Substantial, written off |
| Category: | Accident |
| Location: | Thompson Airport, MB (YTH) -
 Canada
|
| Phase: | Landing |
| Nature: | Ferry/positioning |
| Departure airport: | Gods River Airport, MB (ZGI/CZGI) |
| Thompson Airport, MB (YTH/CYTH) | |
| Investigating agency: | TSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
On 31 October 2017, a Perimeter Aviation Metro III, registration C-FLRY, was operating as flight 959 from Winnipeg-James Armstrong Richardson International Airport to Gods River Airport, Canada. After landing and selecting the speed levers low for taxi, the crew received a crew alerting system warning for the left engine oil pressure. The aircraft was then taxied to the ramp and a normal engine shutdown was performed.
The pilot checked the oil level in the left engine and discovered it to be low. A maintenance crew was dispatched to Gods River to inspect and repair the oil pressure issue. After arriving, the maintenance crew added 3 quarts of oil and an inspection of the left engine revealed oil leaking from the engine oil pressure snubber. The aircraft was then parked overnight and arrangements were made to get the parts needed for the repair.
The next day, on 1 November 2017, a new maintenance crew arrived with the required parts and replaced the left engine oil pressure snubber. Following a test run of the left engine, there was no evidence of an oil leak and maintenance released the aircraft back to service. During a pre-flight inspection, the aircraft maintenance engineer (AME) noticed a hydraulic fluid leak. The AME checked the hydraulic reservoir and found it to be low. An inspection of the hydraulic system did not reveal the source of the leak and the aircraft was once again parked overnight.
On 2 November 2017, another maintenance and flight crew were sent to Gods River to address the hydraulic leak and fly the aircraft back to base. After a lengthy inspection and engine run, the maintenance crew could not identify the source of the hydraulic leak. It was determined that a ferry flight permit would be required to fly the aircraft to a company base at Thompson Airport, for further inspection and repair. The aircraft was then inspected and serviced to the degree necessary for the 50-minute flight. Hydraulic fluid was added to the reservoir, and 1 quart of oil was added to the left engine. The left engine and engine compartment were dry and did not show any signs of an oil leak. A ferry flight permit was then issued that stated the aircraft was to be flown with essential crew only and with the landing gear extended. The flight crew then contacted the assistant chief pilot for a pre-flight briefing that included the risk factors associated with the ferry flight and a discussion about potential emergencies and contingencies, including retracting the landing gear for emergency situations only.
At approximately 18:30 on 2 November 2017, the aircraft, operating as Perimeter flight 959, departed Gods River on the ferry flight to Thompson Airport with only the 2 flight crew members on board. Approximately 15 minutes after departure, the crew noticed the left engine oil pressure drop into the yellow band range. The crew then consulted with maintenance operations control in flight and it was decided that if the oil pressure dropped below the yellow band and the oil temperature increased beyond the green band, then the engine was to be shut down.
The crew began executing the Preplanned Engine Shutdown checklist in the quick reference handbook (QRH) so that they would be prepared if the left engine indications changed. The crew retracted the landing gear to reduce drag and received a gear up-and-locked indication. Because the oil temperature remained in the green band, the crew paused the checklist at the point where the generators are to be turned off, and continued flying the aircraft with the left engine running. When the aircraft was approximately 40 nautical miles southeast of Thompson Airport, the flight crew told air traffic control (ATC) that they had received a low oil pressure indication on the left engine and that the engine might need to be shut down. No emergency was declared, but aircraft rescue and firefighting services were put on standby.
During the final approach to runway 24, the crew extended the landing gear. As the aircraft approached the runway threshold, the left engine rpm dropped to 96%. The pilot then adjusted the right engine rpm to counter the differential rpm. Although the left engine oil pressure dropped below the yellow band, the oil temperature indication did not rise and the crew elected to keep the engine running. It was reported that the left engine oil pressure dropped to 16 psi and the engine oil temperature indication never exceeded 88 °C.
The aircraft's initial landing touchdown on runway 24 was on the right main gear, with both engines operating, approximately 1200 feet past the runway threshold. The captain pulled the power levers over the flight idle gate. An engine power surge was heard, and the aircraft began to pitch up and roll to the right. As the upset progressed, the right wing made contact with the runway and the aircraft pivoted around the right wingtip. The nose section then suddenly dropped to the ground and the aircraft came to rest off the runway, approximately 1800 feet past the runway threshold, in an upright position, facing the opposite direction with the engines still running. The engines were shut down using the engine stop and feather control, and the crew exited the aircraft via the left overwing emergency exit. There was no post-impact fire. The occurrence took place at 19:20, during the hours of darkness. The aircraft sustained substantial damage to the fuselage, propellers, landing gear, and right wing.
Findings as to causes and contributing factors:
1. The left engine low oil pressure indications during the previous and the occurrence flights were likely the result of a steady oil leak past the rear turbine air-oil seal assembly.
2. The loss of engine oil pressure resulted in a loss of propeller control authority on landing and the upset of the aircraft.
3. After consultation with maintenance, the crew considered the risks associated with landing single engine and without hydraulic pressure for the nose-wheel steering, and decided to continue the flight with both engines running, even though this was not consistent with the QRH procedures for low oil pressure indications.
4. Carbon deposits that accumulated within the inside diameter of the bellows convolutions interfered with the bellows' ability to expand and to provide a positive seal against the rotor seal.
Accident investigation:
 |
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Sources:
TSB A17C0132
Location
Revision history:
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