# NTSB WPR23LA107: Bell OH-58A, N36FA, Yuma, AZ, February 7, 2023 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Class 3 · Limited · Final report - Date: February 6, 2023, 21:35 local (Feb 7, 2023, 04:35 UTC) - Place: Yuma, AZ · Field near El Prado Estates - Coordinates: 32.6895, -114.54555 - Nearby events: https://openairdocs.org/map.md?lat=32.6895&lon=-114.5456&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering-hover: Unknown or undetermined](https://openairdocs.org/ntsb-events/000) - Highest injury: Minor injuries - Injuries: 1 minor - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 106695 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR23LA107 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/106695/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=106695 - Page: https://openairdocs.org/ntsb/WPR23LA107 ## Probable cause A total loss of engine power for reasons that could not be determined. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Not determined](https://openairdocs.org/ntsb-findings/05000000): Not determined › Not determined · Unknown/Not determined (probable cause); cases with it: [Bell OH-58A, 8 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md?model=1181579), [All aircraft, 2,247 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md) - [Documentation/record keeping: maintenance records](https://openairdocs.org/ntsb-findings/04033025): Organizational issues › Support/oversight/monitoring · Maintenance provider; cases with it: [Bell OH-58A, 1 case](https://openairdocs.org/ntsb-findings/04033025/cases.md?model=1181579), [All aircraft, 16 cases](https://openairdocs.org/ntsb-findings/04033025/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering-hover: Unknown or undetermined](https://openairdocs.org/ntsb-events/000) (defining event); cases with it: [Bell OH-58A, 2 cases](https://openairdocs.org/ntsb-events/000/sequence.md?model=1181579), [All aircraft, 1,703 cases](https://openairdocs.org/ntsb-events/000/sequence.md) ## 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. ## Factual narrative 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 137 aerial 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 helicopter while 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 recentengine 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. ## Aircraft - Registration: [N36FA](https://openairdocs.org/aircraft/N36FA), registered now, S/N 68-16765, built 1968 (OpenAirDocs) - Reported make and model: BELL OH-58A - Registry model: [Bell OH-58A](https://openairdocs.org/model/bell-oh-58a) (registry code 1181579) (OpenAirDocs) - Registry engine: [Allison T63 series](https://openairdocs.org/engine/allison-t63-series) (registry code 03031, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: 68-16765 - Year built: 1968 - Airframe hours: 9629.8 - Engines: Rolls Royce T63-A720 420 horsepower turbo shaft - Damage: Substantial damage - Flight: Aerial application, Part 137 - Operator: Tri Rotor Spray & Chemical - Registered owner: Tri Rotor Spray & Chemical - Airworthiness certificate: Special, Restricted (Special) - Last inspection: Annual, June 2, 2022, 56 hours before - Departed: AZ25, Somerton, AZ - Destination: Same as departure ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 66; injuries: minor; commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review April 1, 2022; seat: right; restraint: 4-point; flight hours: 20,770 total, 7,800 in this make and model, 20,700 as pilot in command, 143 in the last 90 days, 65.7 in the last 30 days, 2.5 in the last 24 hours ## Weather - Conditions: Visual (VMC), Night - Wind: 300° at 7 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 61 °F, dew point 28 °F - Altimeter: 30.02 inHg - Observed at: KNYL, 4 nm away - METAR: METAR KNYL 060457Z AUTO 30007KT 10SM CLR 16/M02 A3002 ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 20230206001639A](https://openairdocs.org/incident/20230206001639A), Feb 6, 2023: Bell OH-58A, Yuma, AZ, Substantial damage. Aircraft took off from the load truck to dump rinse water through the system. At aproximantly 200 yards away and 40 feet up in altitude. The engine quit… ## Docket (15 files) The files NTSB released with the investigation on November 14, 2024, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=106695. 146 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 8 pages, 3.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16533652&FileExtension=pdf&FileName=6120Yuma%20AZ%20N36FA_Redacted-Rel.pdf - Other pertinent forms and reports (item 2, PDF, 1 page, 844 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15095933&FileExtension=pdf&FileName=6120Boling%20narrative%20correction-Rel.pdf - Maintenance records from engine transfer to N36FA (item 3, PDF, 13 pages, 53.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17146110&FileExtension=pdf&FileName=N36FA%20Maintenance%20records%20from%20engine%20transfer%20to%20N36FA_Redacted-Rel.pdf - Arrow falcon exporters LLC inspection guide checklist (item 4, PDF, 20 pages, 71.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17228360&FileExtension=pdf&FileName=Arrow%20Falcon%20Exporters%20LLC%20Inspection%20Guide%20Checklist_Redacted-Rel.pdf - Mm tm 55-1520-228-23-1 (item 5, PDF, 10 pages, 266 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17112790&FileExtension=pdf&FileName=TECH%20MAN%20pg1_61%20-%201_66_2%20TM%2055%201520%20228-Rel.pdf - Mm M250 C20-series omm - 300 hr fuel system inspection (item 6, PDF, 17 pages, 562 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17114096&FileExtension=pdf&FileName=M250%20C20-Series%20OMM%20-%20300%20Hr%20%20Fuel%20System%20Inspection-Rel.pdf - GPS device - specialist's factual report (item 7, PDF, 10 pages, 2.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16374483&FileExtension=pdf&FileName=GPS%20Device%20-%20Specialist%27s%20Factual%20Report_WPR23LA107-Rel.pdf - Attachment 1 to GPS device - specialist's factual report (item 8, CSV, 518 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16374853&FileExtension=csv&FileName=Attachment%201%20to%20GPS%20Device%20-%20Specialist%27s%20Factual%20Report_WPR23LA107-Rel.csv - Pylon whorl mast fracture lab findings email (item 9, PDF, 3 pages, 428 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17106987&FileExtension=pdf&FileName=WPR23LA107%20-%20Yuma,%20AZ%20-%20Materials%20Laboratory%20Examination%20Report%20EMAIL_Redacted-Rel.pdf - Wreckage exam WPR23LA107 (item 10, PDF, 29 pages, 5.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17106997&FileExtension=pdf&FileName=Wreckage%20Exam%20AP%20WPR23LA107%20Master-Rel.pdf - Engine exam notes WPR23LA107 (item 11, PDF, 6 pages, 616 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17107163&FileExtension=pdf&FileName=ENGINE%20EXAM%20NOTES%20WPR23LA107-Rel.pdf - Rr engine investigation report (item 12, PDF, 14 pages, 2.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17140128&FileExtension=pdf&FileName=WPR23LA107%20-%20Rolls-Royce%20Engine%20Report%20-%20Bell%20OH-58A%20-%20Somerton,%20AZ%20FINAL-Rel.pdf - NTSB party form (item 13, PDF, 14 pages, 180 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17106394&FileExtension=pdf&FileName=NTSB_Investigation_Party_Form_Redacted-Rel.pdf - Mor director of maintenance (item 14, PDF, 1 page, 98 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17141679&FileExtension=pdf&FileName=MOR%20Conrad%20M%202-Rel.pdf - Photos (item 15, PDF, 10 pages, 3.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17228374&FileExtension=pdf&FileName=Pic%20file%20WPR23LA107%20Yuma,%20AZ-Rel.pdf From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.