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Location:
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Yuma, Arizona
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Accident Number:
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WPR23LA107
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Date & Time:
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February 6, 2023, 21:35 Local
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Registration:
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N36FA
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Aircraft:
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Bell OH-58A
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Aircraft Damage:
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Substantial
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Defining Event:
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Unknown or undetermined
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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 conducting an agricultural application flight in dark night conditions. He stated that, after completing the chemical application, he landed on the load truck and the hopper was filled with 50 gallons of water to rinse out the applicator system. The pilot departed from the load truck toward an open field about 200 yards away. The pilot stated that, while maneuvering about 40 ft above ground level when the spray tank was almost empty, the helicopter began to “bounce and tilt in all directions,” then “fish-tailed” before the engine lost total power. The pilot stated that he was unable to judge the helicopter’s height above the ground, and the helicopter subsequently landed hard, during which the main rotor blades severed the tail rotor drive shaft.
Postaccident examination of the helicopter and engine revealed no anomalies or malfunctions that would have precluded normal operation. About 5 gallons of fuel was found in the fuel tank, 1.4 gallons of which was unusable. No engine abnormalities were found during an engine run on a test stand.
Based on the available information, the reason for the loss of engine power could not be determined.
Probable Cause and Findings
The National Transportation Safety Board determines the probable cause(s) of this accident to be: A total loss of engine power for reasons that could not be determined.
Findings
Not determined (general) - Unknown/Not determined
Organizational issues Maintenance records - Maintenance provider
Factual Information
History of Flight
Maneuvering-hover Unknown or undetermined (Defining event)
On February 6, 2023, about 2140 mountain standard time, a Bell OH-58A helicopter, N36FA, was substantially damaged when it was involved in an accident near Yuma, Arizona. The commercial pilot sustained minor injuries. The helicopter was operated as a Title 14 Code of Federal Regulations Part 137aerial application flight.
The pilot stated that he landed in night conditions on the load truck and the chemical hopper was filled with 50 gallons of water to rinse out the applicator system. The pilot departed from the load truck toward an open field about 200 yards away. While maneuvering about 40 ft above ground level, with a speed near effective translational lift, and about 80% transmission torque, the helicopter suddenly started to bounce and yaw. The pilot stated that, when the spray tank was almost empty, the helicopter began to “bounce and tilt in all directions,” then “fish-tailed” before the engine lost total power. The pilot arrested the helicopter’s forward movement by pulling back on the control stick and leveled the helicopterwhile lowering the collective. Unable to judge his height above the ground, the pilot alternately raised and lowered the collective to control the descent, and the helicopter landed hard in the dirt field, and a main rotor blade struck and severed the tail rotor driveshaft. The main rotor and blades assembly separated from the mast and landed about 100 ft from the upright helicopter, as shown in Figure 1.
Figure 1 - Main rotor yoke and blades (Photo courtesy of operator)
The airframe had accrued a total of 9,629.8 hours at the time of the accident; its most recent annual inspection was 8 months before the accident. Flight control continuity was established from the cyclic and collective control to the hydraulic servos and from the hydraulic servos to the non-rotating swashplate. Flight control continuity was established from the anti-torque pedals to the tail rotor pitch control rods. Continuity was established from the throttle twist grip to the fuel control, and from the collective to the fuel governor. The master fuel valve lever was observed in the ON position. Fuel was present from the airframe filter to the fuel spray nozzle. A visual assessment of the fuel remaining found approximately 5 gallons of clean and clear fuel in the fuel tank. The fuel quantity gauge, when energized, did not display an accurate depiction of the actual amount of fuel on board, registering near zero. The fuel supply hose from the airframe fuel filter canister to the engine fuel pump inlet was removed. Fuel dripped from the engine fuel pump after the hose was removed. The fuel pump was found operable when power was applied to it. A general visual inspection of the engine’s various fuel, oil, air, and electrical connections, including B-nuts, indicated that they were tight and painted with torque stripe.
The helicopter was powered by an Allison M250-C20C (T-63-A720), a turbo-shaft, gas-coupled free-power turbine engine. The most recent engine replacement was annotated in the engine logbook and was completed on October 18, 2022, about 4 months before the accident flight. The most recent 100-hour inspection was completed on December 27, 2022, at an aircraft total time of 9,573.8 hours. During a postaccident test run, the engine produced sufficient power and revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation.
Pilot Information
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Certificate:
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Commercial
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Age:
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66,Male
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Airplane Rating(s):
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Single-engine land; Multi-engine
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Seat Occupied:
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Right
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land
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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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Airplane
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Second Pilot Present:
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Instructor Rating(s):
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None
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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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June 17, 2022
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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 1, 2022
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Flight Time:
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20770 hours (Total, all aircraft), 7800 hours (Total, this make and model), 20700 hours (Pilot In
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Command, all aircraft), 143 hours (Last 90 days, all aircraft), 65.7 hours (Last 30 days, all
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aircraft), 2.5 hours (Last 24 hours, all aircraft)
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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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N36FA
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Model/Series:
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OH-58A
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Aircraft Category:
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Helicopter
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Year of Manufacture:
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1968
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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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68-16765
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Landing Gear Type:
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None; High skid
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Seats:
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2
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Date/Type of Last
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June 2, 2022 Annual
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Certified Max Gross Wt.:
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3200 lbs
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Inspection:
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Time Since Last Inspection:
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56 Hrs
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Engines:
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1 Turbo shaft
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Airframe Total Time:
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9629.8 Hrs at time of accident
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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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T63-A720
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Registered Owner:
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TRI ROTOR SPRAY &
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Rated Power:
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420 Horsepower
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CHEMICAL
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Operator:
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TRI ROTOR SPRAY &
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Operating Certificate(s)
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Agricultural aircraft (137)
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CHEMICAL
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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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Night
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Observation Facility, Elevation:
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KNYL,213 ft msl
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Distance from Accident Site:
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4 Nautical Miles
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Observation Time:
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20:57 Local
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Direction from Accident Site:
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237°
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Lowest Cloud Condition:
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Clear
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Visibility
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10 miles
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Lowest Ceiling:
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None
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Visibility (RVR):
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Wind Speed/Gusts:
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7 knots /
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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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300°
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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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30.02 inches Hg
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Temperature/Dew Point:
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16°C / -2°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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Somerton, AZ (AZ25)
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Type of Flight Plan Filed:
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None
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Destination:
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Yuma, AZ
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Type of Clearance:
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None
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Departure Time:
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18:35 Local
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Type of Airspace:
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Class D
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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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32.6895,-114.54555
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Longitude:
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Administrative Information
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Investigator In Charge (IIC):
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Johnson, Scott
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Additional Participating
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Ryan Armenta; Federal Aviation Administration; Scottsdale, AZ
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Persons:
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Daniel Gilligan; Federal Aviation Administration; Scottsdale, AZ
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Original Publish Date:
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November 14, 2024
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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=106695
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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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