# NTSB WPR17LA071: Bell 206B, N211CS, Firebaugh, CA, March 1, 2017 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: March 1, 2017, 10:30 local (18:30 UTC) - Place: Firebaugh, CA - Coordinates: 36.881389, -120.466392 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=36.8814&lon=-120.4664&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering-low-alt flying: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report November 6, 2018 - Report: Approved by Office Director - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration, Bell, Rolls Royce - NTSB case key (mKey): 94799 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR17LA071 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/94799/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=94799 - Page: https://openairdocs.org/ntsb/WPR17LA071 ## Probable cause A total loss of engine power due to fuel exhaustion. Contributing to the accident was the improper calibration of the fuel quantity gauge, which led the pilot to believe that there was adequate fuel onboard. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Fluids: fuel](https://openairdocs.org/ntsb-findings/01071010): Aircraft › Fluids/misc hardware · Fluid management (probable cause); cases with it: [Bell 206B, 15 cases](https://openairdocs.org/ntsb-findings/01071010/cases.md?model=1181511), [All aircraft, 1,695 cases](https://openairdocs.org/ntsb-findings/01071010/cases.md) - [Fluids: fuel](https://openairdocs.org/ntsb-findings/01071010): Aircraft › Fluids/misc hardware · Fluid level (probable cause); cases with it: [Bell 206B, 15 cases](https://openairdocs.org/ntsb-findings/01071010/cases.md?model=1181511), [All aircraft, 1,695 cases](https://openairdocs.org/ntsb-findings/01071010/cases.md) - [Fuel system: fuel quantity indicator](https://openairdocs.org/ntsb-findings/01022841): Aircraft › Aircraft systems · Malfunction (probable cause); cases with it: [Bell 206B, 1 case](https://openairdocs.org/ntsb-findings/01022841/cases.md?model=1181511), [All aircraft, 35 cases](https://openairdocs.org/ntsb-findings/01022841/cases.md) - [Fuel system: fuel indication system](https://openairdocs.org/ntsb-findings/01022840): Aircraft › Aircraft systems · Malfunction (probable cause); cases with it: [Bell 206B, 1 case](https://openairdocs.org/ntsb-findings/01022840/cases.md?model=1181511), [All aircraft, 30 cases](https://openairdocs.org/ntsb-findings/01022840/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering-low-alt flying: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event); cases with it: [Bell 206B, 17 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=1181511), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) - [Enroute-cruise: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Bell 206B, 21 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=1181511), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) - [Autorotation: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Bell 206B, 21 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=1181511), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) ## Analysis The commercial pilot of the helicopter reported that, while conducting an aerial application flight, he heard a loud bang followed by a total loss of engine power. The pilot initiated an autorotation to a plowed field; however, during the landing sequence, the main rotor blades struck the tailboom. Postaccident examination revealed that, when power was applied, the fuel quantity gauge indicated about 15 gallons of fuel when the actual amount present was about 6.5 gallons. This erroneous fuel level indication led the pilot to believe that more fuel was available than was actually in the fuel tanks. The helicopter flight manual indicated that, due to possible fuel sloshing in unusual attitudes or out-of-trim conditions, and one or both fuel pumps inoperative, the unusable fuel is 10 gallons. The engine was subsequently installed on a test stand and several test runs revealed no anomalies. Further testing revealed that the aft fuel boost pump was inoperative. The thermal fuse was found open, consistent with overheating due to the lack of fuel being transferred through the pump. It is likely that, during the flight, the attitude of the helicopter was slightly nose-down. This allowed the fuel to transfer to the forward portion of the tank, which resulted in a lack of fuel flow through the aft fuel pump; the subsequent overheating triggered the thermal fuse, which caused the aft fuel pump to become inoperative. It is likely that the total loss of engine power was the result of fuel exhaustion. ## Factual narrative On March 1, 2017, about 1030 Pacific standard time, a Bell 206B helicopter, N211CS, was substantially damaged during a forced landing following a loss of engine power near Firebaugh, California. The commercial pilot was not injured. The helicopter was registered to and operated by West Valley Aviation Inc., under the provisions of Title 14 Code of Federal Regulations Part 137. Visual meteorological conditions prevailed, and no flight plan was filed for the local aerial application flight, which originated from a nearby staging area about 1 minute prior to the accident. The pilot reported that during an agricultural aerial application flight, he was flying about 5 ft over the crop at an airspeed of 70 mph, when he heard a loud bang followed by a loss of engine power. The helicopter shook violently as he rolled down the throttle twist-grip to the detent stop. As he reached over with his right hand to press the throttle detent switch, he inadvertently rolled on the throttle slightly and heard the engine begin to spool up in RPM, at which time he was able to reach the throttle detent switch to close the throttle. An autorotation was executed and upon touchdown in a freshly plowed soft field, the main rotor blade struck the tailboom and the helicopter came to rest upright. The pilot stated that he had refueled the helicopter about 20 minutes prior to the accident with 20 to 25 gallons of fuel. He estimated that at the time of the accident, he had about 10 gallons of fuel on board. Postaccident examination of the helicopter by the pilot revealed that the tailboom was separated forward of the tail rotor gearbox. The helicopter was recovered to a secure location for further examination. Examination of the helicopter by representatives of Bell Helicopter and Rolls Royce under the supervision of a Federal Aviation Administration inspector revealed that when power was applied to the helicopter, the fuel quantity gauge indicated about 15 gallons of fuel. The fuel tank was drained and contained about 6.5 gallons of fuel. When the fuel was poured into the fuel tank, the fuel quantity gauge displayed about 6 gallons. The forward boost pump was found operational; however, the aft boost pump was inoperative. No preimpact anomalies were observed with the main rotor assembly, main rotor drive system, or flight controls. The engine was removed and subsequently sent to Keystone Aviation for further examination. The engine was installed on a test stand and subsequently run. Throughout 6 test runs, the engine appeared to run normally with the exception of various chip detector lights throughout about 33 minutes of total run time. The engine was disassembled to gain access to the gearbox. Damage was noted to the forward face of the separator on the #3 bearing, which could have been sustained during replacement of the double lip seal with a single lip seal to accommodate the engine test run. No additional anomalies were noted with the engine. Examination of the fuelpump revealed that the thermal fuse was open consistent with over-heating. Representatives from Parker Hannifin stated that the fuel pump thermal fuse is designed to shut power off to the fuel pump when the fuel pump casing builds excess heat due to being run without fluid (fuel). The Bell Helicopter Flight Manual, section 3, page 3-8, states "Due to possible fuel sloshing in unusual attitudes or out of trim conditions, and one or both fuel pumps inoperative, the unusable fuel is ten gallons. ## Aircraft - Registration: [N211CS](https://openairdocs.org/aircraft/N211CS), registered now, S/N 2775 (OpenAirDocs) - Reported make and model: BELL 206B (B) - Registry model: [Bell 206B](https://openairdocs.org/model/bell-206b) (registry code 1181511) (OpenAirDocs) - Registry engine: [Rolls-Royce 250-C20B](https://openairdocs.org/engine/rolls-royce-250-c20b) (registry code 54385, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: 2775 - Year built: 1979 - Engines: ROLLS-ROYCE 250-C20B 420 horsepower turbo shaft - Damage: Substantial damage - Flight: Aerial application, Part 137 - Operator: West Valley Aviation Inc - Registered owner: West Valley Aviation Inc - Airworthiness certificate: Standard, Normal; Special, Restricted (Special) - Last inspection: Continuous airworthiness, February 22, 2017, 20 hours before - Departed: Firebaugh, CA - Destination: Firebaugh, CA - Equipment: None ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 46; injuries: none; commercial; medical: class 2, without waivers/limitations; seat: right; restraint: 4-point; flight hours: 4,599 total, 4,200 in this make and model, 4,559 as pilot in command, 160 in the last 90 days, 100 in the last 30 days, 3.7 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 54 °F, dew point 41 °F - Altimeter: 30.42 inHg - Observed at: KMAE, 18 nm away ## Docket (7 files) The files NTSB released with the investigation on July 5, 2018, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=94799. 18.3 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 5.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40464748&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Bell Report (item 2, .PDF, 140 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40464749&FileExtension=.PDF&FileName=Bell%20Report-Master.PDF - Rolls Royce Report (item 3, .PDF, 5.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40464750&FileExtension=.PDF&FileName=Rolls%20Royce%20Report-Master.PDF - Parker Hannifin Fuel Pump Report (item 4, .PDF, 6.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40464751&FileExtension=.PDF&FileName=Parker%20Hannifin%20Fuel%20Pump%20Report-Master.PDF - Portion of the Bell Helicopter Flight Manual (item 5, .PDF, 54 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40464752&FileExtension=.PDF&FileName=Portion%20of%20the%20Bell%20Helicopter%20Flight%20Manual-Master.PDF - Bell Helicopter Email Correspondence Regarding Flight Manual Usage (item 6, .PDF, 210 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40464753&FileExtension=.PDF&FileName=Bell%20Helicopter%20Email%20Correspondence%20Regarding%20Flight%20Manual%20Usage-Master.PDF - Release of Aircraft Wreckage, NTSB Form 6120.15 (item 7, .PDF, 95 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40464754&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Master.PDF From the NTSB's public API. 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