NTSB Final Report: Garey, CA
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Location:
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Garey, California
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Accident Number:
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WPR24LA093
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Date & Time:
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February 23, 2024, 07:40 Local
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Registration:
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N2618W
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Aircraft:
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Bell 47G-3B-1
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Aircraft Damage:
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Substantial
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Defining Event:
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Loss of engine power (total)
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Injuries:
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1 Minor
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Flight Conducted Under:
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Part 137: Agricultural
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Analysis
The pilot of the helicopter was applying a chemical to a field when the engine sustained a loss of power. The pilot entered an autorotation and the helicopter descended to the terrain, where it rolled onto its right side substantially damaging the main rotor system and severing the tailboom.
Postaccident examination of the pneumatic air lines revealed that there was a slight air leak at the accumulator and a large air leak at a pneumatic air line (Pc) between the power turbine governor (PTG) and the fuel control unit (FCU); the Pc line was not connected to the FCU. The B-nut connecting the Pc line to the FCU had backed off, allowing the Pc line to become disconnected. . This Pc line is one of several lines that use air pressure to communicate fuel scheduling commands between the PTG and the FCU. The security of this line is necessary for proper engine operation. Engine operation without the Pc line properly connected would result in the FCU reducing fuel to a sub-idle condition, preventing the engine from producing sufficient power for continued flight.
No other preaccident mechanical malfunctions or failures were found that would have precluded normal operation.
Maintenance was performed on the helicopter 15 days and 29.2 flight hours before the accident that included checking all B-nuts for torque paint to ensure adequate torque remained on the B-nuts. Maintenance personnel likely did not properly inspect the condition of the torque paint on the affected B-nut, which resulted in a disconnection of the B-nut from the FCU and a total loss of engine power.
Probable Cause and Findings
The National Transportation Safety Board determines the probable cause(s) of this accident to be:
Maintenance personnel’s failure to properly check the torque paint on a fuel control unit B-nut, which resulted in the loosening of the B-nut, a loss of engine power at a low altitude, and a subsequent impact with terrain.
Findings
Aircraft Fuel control/carburetor - Incorrect service/maintenance
Aircraft Climb capability - Attain/maintain not possible
Personnel issues Scheduled/routine maintenance - Maintenance personnel
Factual Information
History of Flight
Maneuvering-low-alt flying Loss of engine power (total) (Defining event)
On February 23, 2024, about 0740 Pacific standard time, a Bell 47G-3B-1, N2618W, was substantially damaged when it was involved in an accident near Garey, California. The pilot received minor injuries. The helicopter was operated as a Title 14 Code of Federal Regulations Part 137 aerial application flight.
According to the pilot, he was about 5 ft above ground level (agl) at an airspeed of 40 knots conducting an aerial application of fungicide on a field when he then initiated a climb to clear a set of power lines. As he increased power for the climb, he noticed the engine out/low rotor audible warning and the engine simultaneously exhibited a loss of power. He performed an autorotation to an off-airport site. During the autorotation the helicopter entered an uncommanded roll to the left. Despite his control inputs, the pilot was unable to arrest the roll and the helicopter impacted terrain in a nose-down, left-side-low attitude. The helicopter came to rest on its right side with substantial damage to the tailboom and main rotor system.
Postaccident examination of the airframe revealed the fuselage exhibited impact damage to the right side. The right skid fractured at the struts and separated from the fuselage. The bubble canopy fractured and separated from the fuselage. The tailboom exhibited a fracture and separation consistent with impact from the main rotor blades.
Postaccident examination revealed the engine remained secured to the airframe by the mounts. Manual rotation of the main engine driveshaft resulted in the rotation of the stage four turbine wheel, confirming continuity of the N2 drivetrain. Motoring the engine by the starter generator resulted in smooth rotation of the compressor rotor, confirming continuity of the N1 drivetrain. Engine control continuity was confirmed from the throttle to the fuel control unit. All engine oil and fuel lines were found secured with all B-nuts being at least hand tight and with no evidence of leakage.
A check of the pneumatic system by application of about 25 psi of air pressure at the Pc filter resulted in the detection of minor air leakage at both B-nuts on both ends of the accumulator and a large leak at the PTG to FCU Pc input line. Closer examination revealed the B-nut had no thread engagement and had slid aft down the Pc line, as shown in figure 1. The input union on the FCU exhibited evidence of green colored torque paint that was similar in color to the other B-nuts and inputs on the FCU.
Figure 1. Image of the accident fuel control, showing the B-nut, the flared end of the Pc line, and the threads of the attachment fitting of the fuel control.
According to Rolls-Royce, the engine manufacturer, the Pc line connecting the PTG to the FCU is the third of three Pc lines in the system. Pc air is the power supply or motive force that allows the fuel control to modulate fuel delivered to the engine fuel nozzle. With this line disconnected, the engine would reduce power to an unpowered static-state or sub-idle condition.
Further examination of the fuel control, fuel governor, and fuel nozzle revealed normal operation. No other preaccident mechanical malfunctions or failures with the engine or airframe were found that would have precluded normal operation.
According to maintenance records, on June 23, 2023, the fuel control was installed on the accident engine along with several other engine components, including the fuel pump, governor, fuel nozzle, bleed control assembly, and a tachometer generator.
On February 8, 2024, about 15 days before the accident, at a Hobbs time of 902.5, a maintenance facility completed the 150-hour/300-hour engine inspections, along with several airframe inspections. According to the Rolls-Royce Alternate Inspection Schedule, the 150/300-hour inspection states, in part, “Inspect all B-nuts for application and alignment of torque paint. If missing, loosen the B-nut, retighten, and apply torque paint.” The Hobbs meter at the time of the accident read 931.7. The maintenance technician who signed off the work did not recall the specifics of the annual inspection conducted on February 8, 2024, as he did several inspections during the shift, but did report the use of the checklists for each inspection.
Rolls-Royce released commercial service letter (CSL) 2373 that addressed a special tool to access the subject B-nut. The CSL provides details on how to manufacture the tool locally and the tool is also available for purchase.
Pilot Information
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Certificate:
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Commercial
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Age:
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63,Male
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Airplane Rating(s):
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None
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Seat Occupied:
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Left
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Other Aircraft Rating(s):
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Helicopter
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Restraint Used:
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4-point
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Instrument Rating(s):
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Helicopter
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Second Pilot Present:
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Instructor Rating(s):
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Helicopter
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Toxicology Performed:
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Medical Certification:
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Class 2 With waivers/limitations
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Last FAA Medical Exam:
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April 13, 2023
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Occupational Pilot:
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Yes
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Last Flight Review or Equivalent:
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April 2, 2022
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Flight Time:
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15000 hours (Total, all aircraft), 15000 hours (Total, this make and model)
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Aircraft and Owner/Operator Information
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Aircraft Make:
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Bell
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Registration:
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N2618W
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Model/Series:
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47G-3B-1
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Aircraft Category:
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Helicopter
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Year of Manufacture:
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1966
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Amateur Built:
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Airworthiness Certificate:
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Restricted (Special)
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Serial Number:
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6580
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Landing Gear Type:
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Skid
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Seats:
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2
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Date/Type of Last
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February 8, 2024 Annual
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Certified Max Gross Wt.:
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2950 lbs
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Inspection:
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Time Since Last Inspection:
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Engines:
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1 Turbo shaft
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Airframe Total Time:
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12450.7 Hrs
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Engine Manufacturer:
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Rolls-Royce
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ELT:
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Not installed
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Engine Model/Series:
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250 SERIES
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Registered Owner:
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ENGLISH AIR SERVICE LLC
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Rated Power:
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420 Horsepower
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Operator:
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ENGLISH AIR SERVICE LLC
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Operating Certificate(s)
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Agricultural aircraft (137)
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Held:
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Meteorological Information and Flight Plan
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Conditions at Accident Site:
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Visual (VMC)
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Condition of Light:
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Day
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Observation Facility, Elevation:
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KSMX,243 ft msl
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Distance from Accident Site:
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6 Nautical Miles
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Observation Time:
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07:51 Local
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Direction from Accident Site:
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272°
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Lowest Cloud Condition:
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Visibility
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9 miles
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Lowest Ceiling:
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Broken / 20000 ft AGL
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Visibility (RVR):
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Wind Speed/Gusts:
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/
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Turbulence Type
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None / None
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Forecast/Actual:
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Wind Direction:
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Turbulence Severity
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N/A / N/A
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Forecast/Actual:
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Altimeter Setting:
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30.08 inches Hg
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Temperature/Dew Point:
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8°C / 7°C
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Precipitation and Obscuration:
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No Obscuration; No Precipitation
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Departure Point:
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Santa Maria, CA (SMX)
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Type of Flight Plan Filed:
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Company VFR
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Destination:
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Santa Maria, CA (SMX)
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Type of Clearance:
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None
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Departure Time:
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06:45 Local
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Type of Airspace:
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Class D
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Airport Information
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Airport:
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Santa Maria SMX
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Runway Surface Type:
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Airport Elevation:
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261 ft msl
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Runway Surface Condition:
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Vegetation
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Runway Used:
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IFR Approach:
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None
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Runway Length/Width:
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VFR Approach/Landing:
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None
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Wreckage and Impact Information
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Crew Injuries:
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1 Minor
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Aircraft Damage:
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Substantial
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Passenger
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N/A
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Aircraft Fire:
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None
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Injuries:
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Ground Injuries:
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Aircraft Explosion:
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None
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Total Injuries:
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1 Minor
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Latitude,
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34.894958,-120.32216(est)
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Longitude:
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Administrative Information
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Investigator In Charge (IIC):
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Salazar, Fabian
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Additional Participating
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David Riser; Rolls-Royce; Indianapolis, IN
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Persons:
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Jerry Dees; Federal Aviation Administration; Van Nuys, CA
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Original Publish Date:
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July 23, 2025
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Last Revision Date:
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Investigation Class:
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Class 3
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Note:
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The NTSB did not travel to the scene of this accident.
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Investigation Docket:
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https://data.ntsb.gov/Docket?ProjectID=193831
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The National Transportation Safety Board (NTSB) is an independent federal agency charged by Congress with investigating every civil aviation accident in the United States and significant events in other modes of transportation— railroad, transit, highway, marine, pipeline, and commercial space. We determine the probable causes of the accidents and events we investigate, and issue safety recommendations aimed at preventing future occurrences. In addition, we conduct transportation safety research studies and offer information and other assistance to family members and survivors for each accident or event we investigate. We also serve as the appellate authority for enforcement actions involving aviation and mariner certificates issued by the Federal Aviation Administration (FAA) and US Coast Guard, and we adjudicate appeals of civil penalty actions taken by the FAA.
The NTSB does not assign fault or blame for an accident or incident; rather, as specified by NTSB regulation, “accident/incident investigations are fact-finding proceedings with no formal issues and no adverse parties … and are not conducted for the purpose of determining the rights or liabilities of any person” (Title 49 Code of Federal Regulations section 831.4). Assignment of fault or legal liability is not relevant to the NTSB’s statutory mission to improve transportation safety by investigating accidents and incidents and issuing safety recommendations. In addition, statutory language prohibits the admission into evidence or use of any part of an NTSB report related to an accident in a civil action for damages resulting from a matter mentioned in the report (Title 49 United States Code section 1154(b)). A factual report that may be admissible under 49 United States Code section 1154(b) is available here.
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