What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
On August 13, 2019, a Bell 206B jetranger was returning to base in olympia, Washington when the pilot noticed an unusual odor, and noted the engine oil pressure was falling below the minimum pressure limits. The pilot decided to make a precautionary landing in an open field located in Tumwater Washington. During the landing event, the engine chip detector caution light also illuminated.
The operator reported significant venting of engine oil was found in the aircraft engine compartment, and on the helicopter?s main rotor blades.
The operator recovered the aircraft by ground transportation back to their base of operations near olympia airport.
On August 14, 2019, the engine was examined in the aircraft by seattle flight standards office personnel, and northwest helicopters maintenance technicians. The following actions were performed:
1. The engine gearbox chip detectors were removed and examined. Significant ferrous material was noted on the detectors.
2. The engine gearbox was drained of oil. 4 quarts of oil were recovered from the gearbox.
3. The engine oil tank was drained of oil. 24 ounces of oil was recovered. (6.5 quart capacity).
4. Oil return and vent hoses from the engine to the engine oil tank were removed and checked for condition. No blockage was noted.
5. The engine airframe mounted scavenge oil filter was removed and checked for condition. The filter was clean, but only residual oil was noted in the filter bowl, signifying lack of oil flow.
6. The engine pressure feed oil filter was removed and checked for condition. The filter was clean, but a smaller amount of oil was noted in the filter cavity than normal.
7. A flashlight and mirror were used to inspect the lower engine chip detector port in the gearbox. Significant pieces of metal were noted. Using a magnet, the metal was removed, and appeared to be oil pump impeller parts.
8. Significant resistance and grinding of the N1 gear train was noted when rotated at the starter generator drive pad.
9. The N2 drive system could not be rotated by turning the number 4 turbine wheel by hand through the engine exhaust port.
It appears the cause of the low oil pressure event was the failure of the engine oil system scavenge pump inside the gearbox. Failure of this pump would not return the oil in the gearbox to the engine oil tank, causing cavitation of the engine oil pressure pump. This is supported by the oil pump parts recovered from the chip detector port, the lack of metal in the engine oil filters, and the small amount of oil found in the oil filter bowl and cavity.
The cause of the oil pump failure will require further disassembly of the engine gearbox.
Operator to submit malfunction defect report for this incident.
The engine gearbox is a ?on condition? Component of the engine, with no manufacturer?s recommended overhaul period.
Engine gearbox p/n 689471, s/n CAG-20859F history:
Total time: 15111.4 hours. Time since overhaul: 4237.4 hours. Time since last repair 319.1.
As the FAA filed it
ON AUGUST 13, 2019, A BELL 206B JETRANGER WAS RETURNING TO BASE IN OLYMPIA, WASHINGTON WHEN THE PILOT NOTICED AN UNUSUAL ODOR, AND NOTED THE ENGINE OIL PRESSURE WAS FALLING BELOW THE MINIMUM PRESSURE LIMITS. THE PILOT DECIDED TO MAKE A PRECAUTIONARY LANDING IN AN OPEN FIELD LOCATED IN TUMWATER WASHINGTON. DURING THE LANDING EVENT, THE ENGINE CHIP DETECTOR CAUTION LIGHT ALSO ILLUMINATED.
THE OPERATOR REPORTED SIGNIFICANT VENTING OF ENGINE OIL WAS FOUND IN THE AIRCRAFT ENGINE COMPARTMENT, AND ON THE HELICOPTER?S MAIN ROTOR BLADES.
THE OPERATOR RECOVERED THE AIRCRAFT BY GROUND TRANSPORTATION BACK TO THEIR BASE OF OPERATIONS NEAR OLYMPIA AIRPORT.
ON AUGUST 14, 2019, THE ENGINE WAS EXAMINED IN THE AIRCRAFT BY SEATTLE FLIGHT STANDARDS OFFICE PERSONNEL, AND NORTHWEST HELICOPTERS MAINTENANCE TECHNICIANS. THE FOLLOWING ACTIONS WERE PERFORMED:
1. THE ENGINE GEARBOX CHIP DETECTORS WERE REMOVED AND EXAMINED. SIGNIFICANT FERROUS MATERIAL WAS NOTED ON THE DETECTORS.
2. THE ENGINE GEARBOX WAS DRAINED OF OIL. 4 QUARTS OF OIL WERE RECOVERED FROM THE GEARBOX.
3. THE ENGINE OIL TANK WAS DRAINED OF OIL. 24 OUNCES OF OIL WAS RECOVERED. (6.5 QUART CAPACITY).
4. OIL RETURN AND VENT HOSES FROM THE ENGINE TO THE ENGINE OIL TANK WERE REMOVED AND CHECKED FOR CONDITION. NO BLOCKAGE WAS NOTED.
5. THE ENGINE AIRFRAME MOUNTED SCAVENGE OIL FILTER WAS REMOVED AND CHECKED FOR CONDITION. THE FILTER WAS CLEAN, BUT ONLY RESIDUAL OIL WAS NOTED IN THE FILTER BOWL, SIGNIFYING LACK OF OIL FLOW.
6. THE ENGINE PRESSURE FEED OIL FILTER WAS REMOVED AND CHECKED FOR CONDITION. THE FILTER WAS CLEAN, BUT A SMALLER AMOUNT OF OIL WAS NOTED IN THE FILTER CAVITY THAN NORMAL.
7. A FLASHLIGHT AND MIRROR WERE USED TO INSPECT THE LOWER ENGINE CHIP DETECTOR PORT IN THE GEARBOX. SIGNIFICANT PIECES OF METAL WERE NOTED. USING A MAGNET, THE METAL WAS REMOVED, AND APPEARED TO BE OIL PUMP IMPELLER PARTS.
8. SIGNIFICANT RESISTANCE AND GRINDING OF THE N1 GEAR TRAIN WAS NOTED WHEN ROTATED AT THE STARTER GENERATOR DRIVE PAD.
9. THE N2 DRIVE SYSTEM COULD NOT BE ROTATED BY TURNING THE NUMBER 4 TURBINE WHEEL BY HAND THROUGH THE ENGINE EXHAUST PORT.
IT APPEARS THE CAUSE OF THE LOW OIL PRESSURE EVENT WAS THE FAILURE OF THE ENGINE OIL SYSTEM SCAVENGE PUMP INSIDE THE GEARBOX. FAILURE OF THIS PUMP WOULD NOT RETURN THE OIL IN THE GEARBOX TO THE ENGINE OIL TANK, CAUSING CAVITATION OF THE ENGINE OIL PRESSURE PUMP. THIS IS SUPPORTED BY THE OIL PUMP PARTS RECOVERED FROM THE CHIP DETECTOR PORT, THE LACK OF METAL IN THE ENGINE OIL FILTERS, AND THE SMALL AMOUNT OF OIL FOUND IN THE OIL FILTER BOWL AND CAVITY.
THE CAUSE OF THE OIL PUMP FAILURE WILL REQUIRE FURTHER DISASSEMBLY OF THE ENGINE GEARBOX.
OPERATOR TO SUBMIT MALFUNCTION DEFECT REPORT FOR THIS INCIDENT.
THE ENGINE GEARBOX IS A ?ON CONDITION? COMPONENT OF THE ENGINE, WITH NO MANUFACTURER?S RECOMMENDED OVERHAUL PERIOD.
ENGINE GEARBOX P/N 689471, S/N CAG-20859F HISTORY:
TOTAL TIME: 15111.4 HOURS. TIME SINCE OVERHAUL: 4237.4 HOURS. TIME SINCE LAST REPAIR 319.1.