Wednesday, February 05, 2020

Loss of Engine Power (Partial): Bell OH-58A, N6251G; accident occurred July 02, 2016 near Brawley Municipal Airport (KBWC), Imperial County, California

Onsite Photo
Federal Aviation Administration

Onsite Photo
Federal Aviation Administration

Onsite Photo
Federal Aviation Administration

Bleed Valve Disassembly
Federal Aviation Administration

Bleed Valve Disassembly
Federal Aviation Administration

Bleed Valve Disassembly 
Federal Aviation Administration

Bleed Valve Disassembly
Federal Aviation Administration

Diaphragm Disassembly
Federal Aviation Administration

Diaphragm Damage
Federal Aviation Administration

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

Additional Participating Entities:

Federal Aviation Administration / Flight Standards District Office; San Diego, California 
Rolls-Royce Corp; Indianapolis, Indiana

Aviation Accident Factual Report - National Transportation Safety Board:

Investigation Docket - National Transportation Safety Board:

Location: Brawley, CA
Accident Number: WPR16LA134
Date & Time: 07/02/2016, 0230 PDT
Registration: N6251G
Aircraft: BELL OH 58A
Aircraft Damage: Substantial
Defining Event: Loss of engine power (partial)
Injuries: 1 None
Flight Conducted Under: Part 137: Agricultural

On July 2, 2016, about 0230 Pacific daylight time, a Bell OH-58A, single-engine, agricultural helicopter, N6251G, experienced a partial loss of engine power while in the vicinity of Brawley Municipal Airport (BWC), Brawley, California. The commercial pilot was not injured. The helicopter was substantially damaged during the precautionary landing to a cropped field. The helicopter was registered to the Bank of Utah, and operated by Farm Aviation, Inc., Brawley, California, as a Title 14 Code of Federal Regulations Part 137 aerial application flight. Night visual meteorological conditions were reported about the time of the accident. A flight plan was not filed for the local flight which departed shortly before the accident.

The pilot reported that after he departed BWC with a full chemical load, he maneuvered about 1/4 mile from the airport and made a 90° turn to line up on the field to be sprayed. Shortly after lining up, the engine started to surge, and the torque meter needle was "bouncing rapidly." The pilot then initiated a precautionary landing. The helicopter landed hard in an open field and came to rest in an upright position.

Examination of the helicopter, which was conducted by a representative from the Federal Aviation Administration (FAA), revealed that the tailboom and tail rotor driveshaft had sustained impact damage consistent with a main rotor strike as a result of the hard landing. The onsite examination of the airframe and engine revealed no anomalies.

Helicopter maintenance documentation was not available during the investigation. According to the pilot, the airframe had a total operating time of 13,688 hours at the time of the accident. The engine had a total operating time of 5,618 hours. The last 100-hour inspection was performed on June 15, 2016, about 74 hours prior to the accident flight.

The helicopter was moved to a secure location and the engine was shipped to a facility for further examination.

Examination of the engine was conducted at Aero Maritime in Phoenix, Arizona on July 28, 2016. An FAA inspector and a Rolls-Royce investigator were present for the examination. The engine was set up in a test cell and during the test run the engine's bleed valve did not close at any speed; the engine produced less than 250 horsepower. When the chip detectors were removed it was revealed that the lower detector had metal debris present and the upper detector had light amounts of metal debris present. When the bleed valve was replaced with an overhauled bleed valve, an additional test run resulted in increased performance rating of about 380 hp being produced (about 7% below minimum allowable power for a serviceable engine) before reaching the maximum specified operating temperature. After the engine test run, the engine was revealed to be unserviceable due to its low power production. No component log card or historical information for the bleed valve was found. According to Rolls-Royce, the compressor, turbine and bleed valve assemblies were overhauled in July 2014, and assembled as an engine. According to Rolls-Royce, the overhaul period for the bleed valve assembly is 1,500 hours. No log cards were available for the bleed valve installed. The engine had 766 hours since overhaul at the time of the accident.

When the accident engine's bleed valve was disassembled it was found that the diaphragm had several holes and cracks. The poppet valve located in the bleed valve assembly, had radial play consistent with worn bushings. According to Rolls-Royce, the non-functioning bleed valve exhibited wear that was not consistent with a bleed valve with comparable service time.

Pilot Information

Certificate: Commercial
Age: 42, Male
Airplane Rating(s): Single-engine Land
Seat Occupied: Right
Other Aircraft Rating(s): Helicopter
Restraint Used:
Instrument Rating(s): Airplane
Second Pilot Present: No
Instructor Rating(s): None
Toxicology Performed: No
Medical Certification: Class 2 Without Waivers/Limitations
Last FAA Medical Exam: 07/29/2015
Occupational Pilot: Yes
Last Flight Review or Equivalent: 05/30/2015
Flight Time:  7000 hours (Total, all aircraft), 1500 hours (Total, this make and model), 7000 hours (Pilot In Command, all aircraft), 150 hours (Last 90 days, all aircraft), 50 hours (Last 30 days, all aircraft), 3 hours (Last 24 hours, all aircraft) 

Aircraft and Owner/Operator Information

Aircraft Make: BELL
Registration: N6251G
Model/Series: OH 58A NO SERIES
Aircraft Category: Helicopter
Year of Manufacture: 1970
Amateur Built: No
Airworthiness Certificate: Restricted
Serial Number: 70-15444
Landing Gear Type: Ski;
Seats: 1
Date/Type of Last Inspection: 06/15/2016, 100 Hour
Certified Max Gross Wt.: 3000 lbs
Time Since Last Inspection: 74 Hours
Engines: 1 Turbo Shaft
Airframe Total Time: 13688 Hours at time of accident
Engine Manufacturer: AMA/EXPR
Engine Model/Series: UNKNOWN ENG
Registered Owner: FARM AVIATION INC
Rated Power: hp
Operating Certificate(s) Held: Agricultural Aircraft (137) 

Meteorological Information and Flight Plan

Conditions at Accident Site: Visual Conditions
Condition of Light: Night
Observation Facility, Elevation: KIPL, -58 ft msl
Distance from Accident Site: 10 Nautical Miles
Observation Time: 0853 UTC
Direction from Accident Site: 198°
Lowest Cloud Condition: Clear
Visibility: 10 Miles
Lowest Ceiling: None
Visibility (RVR):
Wind Speed/Gusts: 9 knots /
Turbulence Type Forecast/Actual:
Wind Direction: 80°
Turbulence Severity Forecast/Actual: 
Altimeter Setting: 29.77 inches Hg
Temperature/Dew Point: 29°C / 18°C
Precipitation and Obscuration: No Obscuration; No Precipitation
Departure Point: Brawley, CA
Type of Flight Plan Filed: None
Destination: Brawley, CA
Type of Clearance: None
Departure Time:  PDT
Type of Airspace: Class G 

Wreckage and Impact Information

Crew Injuries: 1 None
Aircraft Damage: Substantial
Passenger Injuries: N/A
Aircraft Fire: None
Ground Injuries: N/A
Aircraft Explosion: None
Total Injuries: 1 None
Latitude, Longitude: 32.994722, -115.518333 (est)

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