Sunday, January 19, 2020

External Load Event, Sikorsky S-61A, N1043T; accident occurred August 19, 2015 in Ironside, Malheur County, Oregon

GE Aviation

GE Aviation

GE Aviation

GE Aviation

GE Aviation

GE Aviation

GE Aviation

The National Transportation Safety Board did not travel to the scene of this accident.

Additional Participating Entities:
Federal Aviation Administration; Boise, Idaho
GE Aviation; Lynn, Massachusetts
Croman Corp; White City, Oregon
Sikorsky Aircraft; Stratford, Connecticut

Aviation Accident Factual Report - National Transportation Safety Board:

Investigation Docket - National Transportation Safety Board:

Location: Ironside, OR
Accident Number: WPR15LA248
Date & Time: 08/19/2015, 1915 PDT
Registration: N1043T
Aircraft: SIKORSKY S 61A
Aircraft Damage: Substantial
Defining Event: External load event (Rotorcraft)
Injuries: 1 Minor, 1 None
Flight Conducted Under: Part 133: Rotorcraft Ext. Load 

On August 19, 2015, about 1915 Pacific daylight time, a Sikorsky S-61A helicopter, N1043T, experienced a partial loss of power to the No. 2 (right) engine and subsequently landed on a mountainside and rolled over about 7 miles west of Ironside, Oregon. The commercial pilot was not injured; the airline transport pilot sustained minor injuries. The helicopter sustained substantial damage to the tailboom. The helicopter was registered to and operated by Croman Corp as a Title 14 Code of Federal Regulations Part 133 firefighting flight. Visual meteorological conditions prevailed for the flight which operated under a company flight plan. The flight originated from Baker City Municipal Airport (BKE), Baker City, Oregon at 1715.

The commercial pilot reported that they picked up 4,000 pounds of water from a pond then made a climbing left turn to the east towards the fire. About 20 ft above the ground, there was an engine power loss and a drop in RPM. The pilot dumped the water from the bucket at the end of the longline and attempted to gain airspeed and altitude as they entered a small valley. The pilot was keeping the bucket clear of the ground and obstacles when he attempted to release the longline, but it would not fully release from the helicopter fuselage. The second pilot used the emergency throttle, but the engine did not respond; they continued to lose engine RPM and rotor RPM. With the terrain rising, they found the flattest accessible spot and began to slow the helicopter. The pilot landed the helicopter as level as possible, however, the helicopter rolled onto its right side. Prior to the helicopter touching down, the bucket impacted brush and trees and became tangled in a wire fence. 

Pilot Information

Certificate: Commercial
Age: 67, Male
Airplane Rating(s): None
Seat Occupied: Left
Other Aircraft Rating(s): Helicopter
Restraint Used:
Instrument Rating(s): None
Second Pilot Present:Yes 
Instructor Rating(s): None
Toxicology Performed: No
Medical Certification: Class 2 With Waivers/Limitations
Last FAA Medical Exam: 10/14/2014
Occupational Pilot: Yes
Last Flight Review or Equivalent: 04/03/2015
Flight Time:  26062 hours (Total, all aircraft), 14863 hours (Total, this make and model), 24500 hours (Pilot In Command, all aircraft), 145 hours (Last 90 days, all aircraft), 52 hours (Last 30 days, all aircraft), 6 hours (Last 24 hours, all aircraft)

Co-Pilot Information

Certificate: Airline Transport
Age: 65, Male
Airplane Rating(s): Multi-engine Land; Single-engine Land
Seat Occupied: Right
Other Aircraft Rating(s): Helicopter
Restraint Used:
Instrument Rating(s): Helicopter
Second Pilot Present: Yes
Instructor Rating(s): None
Toxicology Performed: No
Medical Certification: Class 2 With Waivers/Limitations
Last FAA Medical Exam: 01/20/2015
Occupational Pilot: Yes
Last Flight Review or Equivalent: 08/15/2015
Flight Time:  17016 hours (Total, all aircraft), 14177 hours (Pilot In Command, all aircraft), 17 hours (Last 90 days, all aircraft), 17 hours (Last 30 days, all aircraft), 6 hours (Last 24 hours, all aircraft)

Aircraft and Owner/Operator Information

Aircraft Make: SIKORSKY
Registration: N1043T
Model/Series: S 61A
Aircraft Category: Helicopter
Year of Manufacture: 1982
Amateur Built:No 
Airworthiness Certificate: Restricted
Serial Number: 61083
Landing Gear Type: Tailwheel
Seats: 2
Date/Type of Last Inspection: 08/09/2015, Continuous Airworthiness
Certified Max Gross Wt.: 21000 lbs
Time Since Last Inspection: 56 Hours
Engines: 2 Turbo Shaft
Airframe Total Time: 40309 Hours as of last inspection
Engine Manufacturer: GE
ELT: Installed, not activated
Engine Model/Series: T58-GE-402
Registered Owner: CROMAN CORP
Rated Power: 1500 hp
Operating Certificate(s) Held: Rotorcraft External Load (133)
Operator Does Business As:
Operator Designator Code: JYEL

The accident helicopter was equipped with two General Electric T58-GE-402 turboshaft military engines. The General Electric T58-GE-402 features a ten-stage axial compressor with variable inlet guide vanes, an annular combustor, a two-stage gas generator turbine, and an independent single stage power turbine.

Maintenance on the helicopter was accomplished by Croman Corp. The last engine light overhaul was completed on August 27, 2014 at which time the helicopter had accumulated 903 hours since major overhaul. This was the first of four light overhauls on the engine that are completed at 1,000-hour intervals. After the fourth light overhaul the TSO is set to zero. The accessory gearbox was separated and examined during the last light overhaul. The last magnetic plug inspection was completed 41.3 hours prior to the accident flight as part of a 35-hour phase inspection. Magnetic plug inspections are required every fourth phase inspection (140 hours). 

Meteorological Information and Flight Plan

Conditions at Accident Site: Visual Conditions
Condition of Light: Day
Observation Facility, Elevation: BKE, 3373 ft msl
Distance from Accident Site: 32 Nautical Miles
Observation Time: 1853 PDT
Direction from Accident Site: 23°
Lowest Cloud Condition: Clear
Visibility:  6 Miles
Lowest Ceiling: None
Visibility (RVR):
Wind Speed/Gusts: 6 knots /
Turbulence Type Forecast/Actual: / None
Wind Direction: 250°
Turbulence Severity Forecast/Actual: / N/A
Altimeter Setting: 29.89 inches Hg
Temperature/Dew Point: 21°C / 11°C
Precipitation and Obscuration: Haze; No Precipitation
Departure Point: Baker City, OR (BKE)
Type of Flight Plan Filed: None
Destination: Baker City, OR (BKE)
Type of Clearance: None
Departure Time: 1715 PDT
Type of Airspace: Unknown

Wreckage and Impact Information

Crew Injuries: 1 Minor, 1 None
Aircraft Damage: Substantial
Passenger Injuries: N/A
Aircraft Fire: None
Ground Injuries: N/A
Aircraft Explosion: None
Total Injuries: 1 Minor, 1 None
Latitude, Longitude: 44.338333, -118.110000 

On scene examination by a Federal Aviation Administration inspector revealed that the bucket was entangled in a barbed wire fence. The line was tight, off the ground, and stretched around a tree before it continued straight towards the main wreckage. Impact damage was consistent with the helicopter impacting the ground on its tailwheel first followed momentarily by main landing gears. The tailwheel was found separated from the airframe and impact marks indicated the tail rotor impacted the ground. In addition, marks consistent with main rotor blade impact were also observed on the ground near the main wreckage.

Examination of the longline revealed that the attachment point on the fuselage of the helicopter indicated that the hook released the longline as expected, however one of the two hydraulic quick disconnect (QD) couplings failed to release. The hard mounted quick disconnect system for the hydraulic lines was examined and it was noted that only one of the fittings released from the coupling. The longline side of the released fitting was undamaged; it had a stretched and fractured a safety wire that was secured to it. The other fitting was fracture separated and did not appear to release from the hard mount system until the helicopter hit the ground. Part of the fitting was still secured to the longline, and the remaining part was still secured to the coupling with a safety wire securing it in place.

Number 1 Engine Examination and Run

Initial visual examination of the number 1 engine revealed minimal damage. The engine was rotated, and continuity was verified through the Ng drivetrain, which included the compressor and gas generator turbine, and Nf drivetrain, which is the independent power turbine spool. The magnetic plugs were removed and all four exhibited light residue accumulation which was considered normal for service run engines according to General Electric and Croman Corp.

The engine was installed into a test cell; the engine started normally and idled with normal indications. Initially, smoke was observed emanating from the power turbine area, however, it ceased after a few minutes of run time. The engine was cycled between idle and about 100% Ng several times to ensure the control system was functioning properly. The fuel control topping set point was checked, and it was recorded at 101.8% Ng, which is 1.9% Ng below manual specifications.

Number 2 Engine Examination

During the examination and disassembly of the number 2 engine, all exterior engine surfaces were intact and in good condition. The magnetic plugs were removed, and all four plugs had metal debris accumulation, with the most debris noted on the accessory gearbox and power turbine accessory plugs. The front frame accessory drive was manually rotated at the inlet, and no concurrent rotation of the centrifugal fuel purifier drive splines was observed. The accessory gearbox, fuel control, and oil lube pump were removed from the engine. The radial driveshaft was then removed from the front frame and scallop shaped wear marks were observed around the shaft, which matched the mating female splines of the pinion assembly. In addition, about 0.10 inch of material wear was observed on the front frame housing consistent with pinion gear assembly contact.

The pinion gear assembly was removed from the accessory gearbox. The pinion gear, which mates with the bevel gear, exhibited wear on the gear teeth and some metal smearing concentrated along the tips, consistent with gear disengagement. The pinion support assembly was disassembled and the upper support bearing exhibited roller ball, bearing cage, and race damage. In addition, the bevel gear exhibited wear on the teeth consistent with what was observed on the mating pinion.

The accessory gearbox pinion, bevel gears, the upper and lower pinion support bearings, and all four magnetic plugs underwent metallurgical examination. An energy dispersive x-ray scan, microstructure analysis, and hardness testing indicated that both the bevel and pinion gears met material specifications. Both the pinion and bevel gears had excessive wear on 50-75% of the outer tooth span at the gear tooth tip, which is also consistent with gear disengagement. In addition, cracks were noted on two adjacent bevel gear teeth.

The pinion upper support bearing was disassembled, and spalling was observed on the balls, inner, and outer raceways. Wear was mostly concentrated on the upper pinion support bearing inner race land. Energy dispersive x-ray and scanning electron microscopy identified aluminum oxide particles embedded in the cage pocket and inner races of both bearings. The debris accumulation on the magnetic plugs was analyzed and found to be consistent with bearing and gear material.

According to the manufacturer, aluminum oxide is not present in any T58-GE-402 bearing or component within the oil lubrication system pathway. Historically, aluminum oxide has been inadvertently introduced into the engine during the engine overhaul/repair process. Aluminum oxide is abrasive and once it is embedded into the bearing it can cause uneven wear and accelerated failure.

No comments:

Post a Comment