# NTSB LAX97GA235: Bell BHT-206L-1, N27591, Highland, CA, July 7, 1997 - Type: NTSB accident investigation - Classification: Accident · Fatal · Final report - Date: July 6, 1997, 17:03 local (Jul 7, 1997, 00:03 UTC) - Place: Highland, CA - Coordinates: 34.130203, -117.150726 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=34.1302&lon=-117.1507&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Highest injury: Fatal - Injuries: 1 fatal - Status: Completed, report September 28, 1999 - Report: Approved by Office Director - NTSB case key (mKey): 29641 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX97GA235 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/29641/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=29641 - Page: https://openairdocs.org/ntsb/LAX97GA235 ## Probable cause Loss of engine power due to fuel contamination. Also causal was the ingestion of entrapped air that occurred during an abrupt maneuver and fuel-borne contamination that caused the fuel system check valves to leak, resulted in a lower than expected fuel level in the main fuel cell. A related factor was mountainous terrain. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Abrupt maneuver, maneuvering - aerial application - fluid,fuel - contamination,other than water (cause) - fluid,fuel - flow restricted (cause) - fuel system,transfer pump - leak (cause) - fuel system,tank - low level (cause) - Loss of engine power(total) - nonmechanical, maneuvering - aerial application - autorotation - initiated, pilot in command - air/ground communications - initiated, pilot in command - Forced landing, emergency descent/landing - In flight collision with terrain/water, emergency descent/landing - terrain condition - mountainous/hilly (contributing factor) ## Analysis The pilot was conducting water dropping operations as part of an ongoing forest fire fighting effort. A firefighter reported that the helicopter made two water drops before the accident. A battalion fire chief, who was directing the effort, reported that he saw the helicopter making water drops on a slope. After a water drop which involved an abrupt pull up and turn after the water was released from the bucket, he reported hearing the words 'May Day,' 'I have a flame out' and finally 'I'm going down'. Several other people who were monitoring the common frequency also reported hearing a transmission with the phrase 'flame out.' The helicopter impacted the bottom of the canyon. An inspection revealed that the lines from the engine fuel nozzle to the fuel control and the airframe fuel filter contained fuel. The lines and in-line filters contained both fuel and particulate matter in the bottom of both filter housings. Testing revealed that the manifold check valve leaked from both inlet ports. When the valves were disassembled additional foreign material was found. The material was found to be a combination of organic and inorganic materials. A 5-gallon fuel sample was taken from the refueling truck on the day of the accident. The analytical report stated that the sample submitted was that of aviation turbine fuel. No contamination was noted. According to historical records, there have been a series of engine flameout related accidents and incidents related to this engine make and model. Controlled tests have demonstrated that should entrapped air migrate through the fuel system to the engine, an engine flame out can occur. ## Factual narrative HISTORY OF FLIGHT On July 6, 1997, about 1703 hours Pacific daylight time, a Bell BHT-206L-1, N27591, operating with the call sign H-520, crashed in the San Bernardino mountains north of Highland, California. The pilot was conducting water dropping operations as part of an ongoing forest fire fighting effort. The aircraft was destroyed and the commercial rated helicopter pilot, the sole occupant, received fatal injuries. The aircraft was being operated by the USDA Forest Service under contract as an exclusive public-use aircraft when the accident occurred. The flight originated about 1630 from the Patton Helibase in Highland, California. Visual meteorological conditions prevailed with localized smoke in the fire areas. No flight plan was filed. About 1630 all helicopters on station were directed to begin dropping water on the Hemlock fire that had just jumped across a fire line. A battalion fire chief, onboard Air Attack 310, was directing the effort. The chief reported that he saw H-527 and H-520 making water drops on a slope in Division B at 1703. The drops involved an abrupt pull up and turn after the water was released from the bucket. As the two aircraft were departing the area, he heard the words "May Day," "I have a flame out" and finally "I'm going down". He then observed H-520 impact the bottom of the canyon. He stated that it appeared to him as if the aircraft's main rotor struck the west canyon wall before the aircraft came to rest. After making a water drop, the pilot of H-527 was heading back to the water point when he saw H-520 heading toward the fire area. A few seconds later he reported hearing "I've got a flame out" and subsequently turned back toward the fire area. He reported seeing a cloud of dust and flew closer to investigate. As he neared the crash site, he saw H-520 on the ground at the bottom of the canyon. A ground scar was visible on the west side of the canyon about 5 to 10 feet from the top. A firefighter with Vista Grande Hotshots, reported that H-520 made two water drops before the accident. Several other people who were monitoring the common frequency also reported hearing a transmission with the phrase "flame out." PERSONNEL INFORMATION The pilot satisfactorily completed initial company training on May 9, 1995. He satisfactorily completed recurrent Bell 206 company training on May 30, 1997. That training included instruction in refueling procedures, fuel consumption computations, emergency procedures, performance characteristics, and operating limitations. He satisfactorily completed a company FAR 135 proficiency check on May 30, 1997. That check required him to perform emergency procedures, simulated engine failures, and autorotations. He had been issued a USDA/USDI Interagency Helicopter Pilot Qualification card on April 7, 1997. The card had an expiration date of April 30, 1998. The card indicated that he was approved for external load operations, fire suppression and retardant/water dropping. A review of the pilot's duty log revealed that he worked 12 days and then had 2 days off duty. His standard duty day was 9 hours but on two occasions he worked 12-hour days. During the preceding month he flew a total of 13.9 hours. He flew on 12 duty days, averaging about 1.2 hours on those days. On June 24th he flew a total of 5 hours. AIRCRAFT INFORMATION The aircraft had originally been manufactured with an Allison 250-C28 engine. The aircraft had a supplemental type certificate for an Allison 250-C30P that was installed at the time of the accident. A review of the aircraft maintenance records revealed entries indicating that the aircraft was being maintained in an airworthy condition. Bell Helicopter Alert Service Bulletin No. 206L-86-41, requiring the airframe fuel filter is modified with a bleed hole for entrapped air had been applied. The aircraft was equipped with a cargo hook that had both manual and electrical cargo releases. The flight following log showed a total of six flights for a total flight time of 6.8 hours. Total fuel onboard, dispensed by the fuel trucks, was computed by the owner and refueler as 240.6 gallons. The refueler reported that the H-520 began the duty day at Trimmer Helibase with 95.6 gallons of fuel. The basis for this statement is the assumption that the fuel quantity gauge was properly calibrated. There was no evidence or history found to suggest it was not operating accurately. The pilot made his first refueling stop at Fox Field in which 30.7 gallons were added. The flight time for the first flight was recorded as 1.3 hours. From Fox Field, the pilot completed the remainder of has flight to Patton Helibase in .7 hours. After arrival at Patton, the pilot flew a reconnaissance flight for 2.2 hours and then external load flight for .8 hours. The aircraft was next refueled with 47 gallons from a from a fuel truck belonging to ERA, another contract company. It was later refueled with an additional 39 gallons from a fuel truck belonging to Rogers Helicopters. The pilot flew another reconnaissance flight for 1.2 hours and then returned for refueling. The refueler reported that he added 14 gallons at that time. The pilot then departed on the sixth and final water dropping flight for .6 hours or until the accident. The operator reported that was standard practice for the pilot to monitor his remaining fuel quantity with a watch. According to the manufacturer, the low fuel light is designed to illuminate at between 7.4 and 11 gallons or between 50 and 75 pounds. The aircraft was equipped with an external 'Bambi' water bucket with a 144-gallon capacity. COMMUNICATIONS A voice, believed to be the pilot's, was heard over the common use frequency. Listeners to the transmission generally agreed that the voice they heard stated "flame out." Of those who replied, all agreed that they did not hear any reply after they responded to the call. The frequency in use at the time of the accident was an internal channel. Consequently, no recording of the communications traffic is available for review. WRECKAGE AND IMPACT INFORMATION The crash site was located .3 mile west of the fire in Little Sand Canyon at 34 degrees 09 minutes 29 seconds north latitude and 117 degrees 13 minutes 26 seconds west longitude. The elevation of the site was about 1,660 feet msl. The terrain at the bottom of the canyon sloped away from the wall toward a creek at approximately -10 degrees. The aircraft came to rest in an upright position on a heading of 252 degrees. The water bucket was still attached to the sling line. Fragments of Plexiglas were found near ground scars at the top of the canyon wall about 50 feet above the final position of the aircraft. Both landing gear skid tubes were separated from the airframe. The forward cross tube was still attached to the fuselage while the aft cross tube was separated from the fuselage with portions of the belly structure remaining attached to the cross tube saddles. The rear cross tube was deformed downward with its lower surface 11.75 inches from a level surface. The main fuselage exhibited multiple examples of overstress fractures. The belly section was fractured at FS stations 43, 96, and 142. The structure surrounding the aft fuel cell was fractured and the fuel cell was ruptured. The roof was fractured downward beneath the transmission. The structure beneath the right front seat was crushed downward 5.5 inches. There was evidence of compression buckling at the base of the center console. The right and left doorposts were fractured, as was the windscreen center post. There was evidence of structural penetration at FS 220. The underside of the nose between the chin bubbles was crushed upward. The manual cargo release functioned when tested. The tailboom was separated at BS (Boom Station) 44. The aft portion of the tailboom wa ## Aircraft - Registration: [N27591](https://openairdocs.org/deregistered/N27591-2013-05-15), registration cancelled 2013-05-15, S/N 45273 (OpenAirDocs) - Reported make and model: Bell BHT-206L-1 - Registry model: [Bell Helicopter Textron 206L-1](https://openairdocs.org/model/bell-helicopter-textron-206l-1) (registry code 1182107) (OpenAirDocs) - Category: Helicopter - Serial number: 45273 - Airframe hours: 7705 - Engines: Allison 250-C30P 650 horsepower turbo shaft - Damage: Destroyed - Flight: Public use - Operator: Usda Forest Service, doing business as Regional Office, R5 - Registered owner: Rogers Helicopters, Inc. - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, May 26, 1997, 39 hours before ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 50; commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, valid medical--no waivers/lim.; seat: right; toxicology performed; flight hours: 11,000 total, 2,900 in this make and model, 61 in the last 90 days, 13 in the last 30 days, 6 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 240° at 16 knots - Visibility: 15 statute miles - Lowest ceiling: none - Temperature: 90 °F, dew point 59 °F - Altimeter: 29.00 inHg - Observed at: ONT, 23 nm away ## Docket (31 files) The files NTSB released with the investigation on March 26, 1999, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=29641. 5.0 MB in all. - Supplement C (item 1, .PDF, 257 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40102926&FileExtension=.PDF&FileName=Supplement%20C-Master.PDF - Supplement D (item 2, .PDF, 344 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40102927&FileExtension=.PDF&FileName=Supplement%20D-Master.PDF - Supplement K (item 3, .PDF, 259 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40102928&FileExtension=.PDF&FileName=Supplement%20K-Master.PDF - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 4, .PDF, 727 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40411738&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Witness Statements (item 5, .PDF, 371 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40411739&FileExtension=.PDF&FileName=Witness%20Statements-Redacted.PDF - Map of the accident area (item 6, .PDF, 135 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40102931&FileExtension=.PDF&FileName=Map%20of%20the%20accident%20area-Master.PDF - Wreckage diagram (item 7, .PDF, 21 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40102932&FileExtension=.PDF&FileName=Wreckage%20diagram-Master.PDF - U.S. Forest Service helicopter data record (item 8, .PDF, 127 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40411740&FileExtension=.PDF&FileName=U.S.%20Forest%20Service%20helicopter%20data%20record-Redacted.PDF - Department of the Interior pilot qualification record (item 9, .PDF, 160 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40411741&FileExtension=.PDF&FileName=Department%20of%20the%20Interior%20pilot%20qualification%20record-Redacted.PDF - U.S. Forest Service flight report (item 10, .PDF, 109 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40411742&FileExtension=.PDF&FileName=U.S.%20Forest%20Service%20flight%20report-Redacted.PDF - Reports from San Bernardino County Sheriff's Office (item 11, .PDF, 176 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40411743&FileExtension=.PDF&FileName=Reports%20from%20San%20Bernardino%20County%20Sheriff%27s%20Office-Redacted.PDF - Rogers Helicopters Inc. record of recurrent training (item 12, .PDF, 243 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40411744&FileExtension=.PDF&FileName=Rogers%20Helicopters%20Inc.%20record%20of%20recurrent%20training-Redacted.PDF - Rogers Helicopters Inc. time and duty log (item 13, .PDF, 64 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40102938&FileExtension=.PDF&FileName=Rogers%20Helicopters%20Inc.%20time%20and%20duty%20log-Master.PDF - Bell Helicopters fuel flow estimate (item 14, .PDF, 33 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40102939&FileExtension=.PDF&FileName=Bell%20Helicopters%20fuel%20flow%20estimate-Master.PDF - Bell Helicopter checklist excerpt (item 15, .PDF, 91 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40411745&FileExtension=.PDF&FileName=Bell%20Helicopter%20checklist%20excerpt-Redacted.PDF - Pilot's Operating Handbook fuel flow charts (item 16, .PDF, 76 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40102941&FileExtension=.PDF&FileName=Pilot%27s%20Operating%20Handbook%20fuel%20flow%20charts-Master.PDF - Allison Engine performance report (item 17, .PDF, 192 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40102942&FileExtension=.PDF&FileName=Allison%20Engine%20performance%20report-Master.PDF - Airframe and engine logbook excerpts (item 18, .PDF, 127 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40102943&FileExtension=.PDF&FileName=Airframe%20and%20engine%20logbook%20excerpts-Master.PDF - Core Lab fuel analysis (item 19, .PDF, 129 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40411746&FileExtension=.PDF&FileName=Core%20Lab%20fuel%20analysis-Redacted.PDF - Circle Seal Control, Inc. manifold check valve (item 20, .PDF, 112 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40411747&FileExtension=.PDF&FileName=Circle%20Seal%20Control,%20Inc.%20manifold%20check%20valve-Redacted.PDF - Circle Seal Control, Inc. check valve (item 21, .PDF, 87 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40411748&FileExtension=.PDF&FileName=Circle%20Seal%20Control,%20Inc.%20check%20valve-Redacted.PDF - Seal Laboratories foreign material analysis (item 22, .PDF, 417 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40411749&FileExtension=.PDF&FileName=Seal%20Laboratories%20foreign%20material%20analysis-Redacted.PDF - Statement of Party Representatives to NTSB Investigation (item 23, .PDF, 261 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40411750&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Redacted.PDF - Release of Aircraft Wreckage, NTSB Form 6120.15 (item 24, .PDF, 49 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40411751&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Redacted.PDF - Toxicological Report (item 25, .PDF, 73 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40102950&FileExtension=.PDF&FileName=Toxicological%20Report-Master.PDF - Photo 1: Aerial view of the accident site. (item 26, .PDF, 50 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40102951&FileExtension=.PDF&FileName=Photo%201%3A%20Aerial%20view%20of%20the%20accident%20site.-Master.PDF - Photo 2: View of the left side of the aircraft. (item 27, .PDF, 65 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40102952&FileExtension=.PDF&FileName=Photo%202%3A%20View%20of%20the%20left%20side%20of%20the%20aircraft.-Master.PDF - Photo 3: Aft view of the aircraft. (item 28, .PDF, 64 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40102953&FileExtension=.PDF&FileName=Photo%203%3A%20Aft%20view%20of%20the%20aircraft.-Master.PDF - Photo 4: Front view of the aircraft. (item 29, .PDF, 53 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40102954&FileExtension=.PDF&FileName=Photo%204%3A%20Front%20view%20of%20the%20aircraft.-Master.PDF - Photo 5: Initial point of impact. (item 30, .PDF, 65 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40102955&FileExtension=.PDF&FileName=Photo%205%3A%20Initial%20point%20of%20impact.-Master.PDF - Photo 6: Fuel boost pump circuit breakers. (item 31, .PDF, 38 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40102956&FileExtension=.PDF&FileName=Photo%206%3A%20Fuel%20boost%20pump%20circuit%20breakers.-Master.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.