# NTSB WPR21LA268: Bell 212HP, N911KW, Weed, CA, July 7, 2021 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: July 7, 2021, 16:45 local (23:45 UTC) - Place: Weed, CA · Lake - Coordinates: 41.537, -122.378 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=41.5370&lon=-122.3780&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering-low-alt flying: External load event (Rotorcraft)](https://openairdocs.org/ntsb-events/480) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: USFS, FAA, TSB, Bell Helicopters Inc, Pratt & Whitney - NTSB case key (mKey): 103465 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR21LA268 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/103465/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=103465 - Page: https://openairdocs.org/ntsb/WPR21LA268 ## Probable cause The pilot’s failure to maintain altitude during an approach to a lake. Contributing to the accident was the pilot’s failure to release the full water bucket as the helicopter was settling, which reduced the helicopter’s out-of-ground-effect performance. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Performance/control parameters: altitude](https://openairdocs.org/ntsb-findings/01062012): Aircraft › Aircraft oper/perf/capability · Not attained/maintained (probable cause); cases with it: [Bell 212, 1 case](https://openairdocs.org/ntsb-findings/01062012/cases.md?model=1181420), [All aircraft, 1,310 cases](https://openairdocs.org/ntsb-findings/01062012/cases.md) - [Info processing/decision: decision making/judgment](https://openairdocs.org/ntsb-findings/02041520): Personnel issues › Action/decision · Pilot; cases with it: [Bell 212, 2 cases](https://openairdocs.org/ntsb-findings/02041520/cases.md?model=1181420), [All aircraft, 3,098 cases](https://openairdocs.org/ntsb-findings/02041520/cases.md) - [Action: lack of action](https://openairdocs.org/ntsb-findings/02041030): Personnel issues › Action/decision · Pilot; cases with it: [Bell 212, 1 case](https://openairdocs.org/ntsb-findings/02041030/cases.md?model=1181420), [All aircraft, 792 cases](https://openairdocs.org/ntsb-findings/02041030/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: External load event (Rotorcraft)](https://openairdocs.org/ntsb-events/480) (defining event); cases with it: [Bell 212, 1 case](https://openairdocs.org/ntsb-events/480/sequence.md?model=1181420), [All aircraft, 51 cases](https://openairdocs.org/ntsb-events/480/sequence.md) - [Maneuvering-low-alt flying: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Bell 212, 3 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=1181420), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The flight was on an approach to a lake to retrieve water for a water bucket drop operation. During the approach, the instruments scanned normal, and the radar altimeter was set to 200 ft above ground level to provide a buffer between the bucket and terrain. When the helicopter crossed the shoreline, the pilot visually confirmed that the 100-ft long line and bucket were slightly trailing the helicopter and had not dipped in the water. Shortly afterward, he felt a “sudden onset of a significant vibration.” The pilot aborted the water retrieval and noticed that helicopter lost altitude. He applied forward cyclic and raised the collective, but the helicopter continued to descend. The pilot realized that he would not be able to fly out of the descent, so he decided to make a forced water landing. The pilot did not jettison the long line and bucket. After he leveled the helicopter and the skids touched down on the water, he made another attempt to take off, but the helicopter settled into the lake. The pilot reduced both throttle settings to idle in preparation to ditch the helicopter and applied right cyclic as the main rotors slowed. The helicopter rolled right, and the main rotor blades struck the water, which resulted in substantial damage to the fuselage, rotor, and drive systems. Postaccident examination of the engine revealed no preimpact mechanical anomalies. The airframe examination revealed an out-of-tolerance condition of both pylon damper rod end bearings that likely caused the vibration reported by the pilot. It is likely that, after the lateral vibration, the pilot allowed the helicopter to descend while he tried to determine the source of the vibration. As the helicopter settled into the lake, the bucket filled with water. The resulting increased weight, combined with the pilot’s failure to release the water bucket, decreased the helicopter’s out-of-ground-effect performance. ## Factual narrative On July 7, 2021, about 1450 Pacific daylight time, a Bell 212 helicopter, N911KW, was substantially damaged when it was involved in an accident near Weed, California. The pilot was not injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 133 external load flight. The pilot reported that he was supporting a US Forest Service contract involving water drop operations and that the accident flight was on approach to a lake to retrieve water using a 100-ft long line and bucket. When the helicopter was about 400 ft above ground level (agl), the pilot performed an instrument scan and noted no anomalies. The pilot added that the radar altimeter was set to 200 ft agl at the time. When the helicopter crossed the shoreline, the pilot observed that the long line and bucket were “not yet in view and still out behind [him].” Shortly afterward, he felt a “sudden onset of a significant vibration,” which he also described as once-per-minute rotation. (An inspector with the US Forest Service explained that the term “indicates an imbalance in main rotor head or main rotor blades.) The pilot scanned the instrument panel and saw no annunciator lights or indications that the engines had stopped producing power. He then glanced outside and realized that the helicopter had descended. The pilot aborted the water retrieval, made a forward cyclic input, and raised the collective, but the helicopter continued to descend. The pilot determined that he would be unable to stop the descent, and he did not want the engines or transmission to overspeed, so he performed a forced landing on water. After he leveled the helicopter and the skids touched down on the water, the pilot made a last attempt to take off, which was unsuccessful. The pilot reduced both throttle settings to idle in preparation to ditch the helicopter and applied right cyclic as the main rotors slowed. The pilot stated that the helicopter controls responded normally and that the helicopter did not yaw significantly. The helicopter rolled right, causing the main rotor blades to strike the water, and the helicopter subsequently sank into the lake. Automatic dependent surveillance-broadcast data showed that the bucket was about 35 ft above the water when the last data point was recorded. At that time, the helicopter's descent rate was about 768 ft per minute. The pilot did not jettison the long line and bucket because he thought that he would be able to fly away. The helicopter sustained substantial damage to the fuselage, main and tail rotor blades, and drive systems. Training records showed that the pilot completed six recurrent long-line training flights from May 3 to 29, 2021. On May 31, 2021, the pilot completed a helicopter pilot evaluation checkride with a US Forest Service pilot inspector and was cleared for solo external-load water bucket operations. The 240-gallon water bucket was configured to gather 90% of its total capacity, which would add an additional weight of about1,966 pounds to the helicopter and increase its 8,150-pound gross weight to about 10,116 pounds. The bucket was recovered attached to the helicopter by a cargo hook and the long line. Postaccident examination of the bucket and engine powerpack revealed no preimpact mechanical malfunctions or failures that would have precluded normal operations. The pylon corner mounts and pylon dampers were hydraulically tested with dynamic loads and exhibited normal operational performance. The rod end bearings for the pylon dampers had tolerances that were more than the Bell 212 Maintenance Repair and Overhaul Manual tolerance of 0.004-inch radial play: the right aft damper bearing play was 0.006 inch, and the left aft damper bearing play was 0.016 inch. According to Bell Textron, the excessive radial clearance of rod end bearings reduces the amount of damper stroking to counteract vibratory motion of the pylon. Also, a flight crew in a separate event experienced a vibration that was traced back to excessive radial wear of the pylon damper rod end bearings. The helicopter’s hover out of ground effect (OGE) performance was computed using the helicopter operator’s Rotorcraft External Load Manual, which included a performance chart from Bell Helicopter’s BHT-212-MD-1 manual. According to the performance chart, at an air temperature of 35°C, heater OFF, engine rpm at 100%, skid height of 50 ft, a 15-knot headwind, and generator values of 150 amperes, the helicopter had an OGE takeoff power gross weight limitation of about 10,250 pounds. According to the Bell 212 Rotorcraft Flight Manual: Supplement Cargo Hook, at a helicopter gross weight of 8,150 pounds, an air temperature of 35°C, heater OFF, engine rpm at 100%, skid height of 60 ft, and generator values of 150 amperes, the helicopter had an OGE takeoff power limitation at a pressure altitude of about 8,000 ft and a maximum continuous power setting limitation at a pressure altitude of about 6,600 ft. The Bell Helicopters manual also showed that, at a gross weight of about 10, 116 pounds, the helicopter had an OGE takeoff power limitation at a pressure altitude of about 3,700 ft and a maximum continuous power setting limitation of 9,300 pounds. ## Aircraft - Registration: [N911KW](https://openairdocs.org/aircraft/N911KW), registered now, S/N 30592, built 1973 (OpenAirDocs) - Reported make and model: BELL 212HP - Registry model: [Bell 212](https://openairdocs.org/model/bell-212) (registry code 1181420) (OpenAirDocs) - Registry engine: [Pratt & Whitney PT6 series](https://openairdocs.org/engine/pratt-whitney-pt6-series) (registry code 52033, turbo-prop) (OpenAirDocs) - Category: Helicopter - Serial number: 30592 - Year built: 1973 - Airframe hours: 14543.5 - Engines: Pratt & Whitney PT6T-3B turbo shaft; Pratt & Whitney PT6T-3B turbo shaft - Damage: Substantial damage - Flight: Firefighting, Part 133 - Operator: Rogers Helicopters Inc - Registered owner: Rogers Helicopters Inc - Airworthiness certificate: Standard, Utility - Last inspection: Continuous airworthiness, June 29, 2021 - Departed: 1O6, Dunsmuir, CA - Equipment: None ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 35; injuries: none; commercial, flight instructor; airplane ratings: single-engine land; instrument ratings: helicopter; medical: class 1; last flight review May 5, 2021; seat: left; restraint: lap only; flight hours: 4,636 total, 239 in this make and model, 4,407 as pilot in command, 19 in the last 90 days, 8 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 20° at 15 knots, gusting 20 - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 93 °F, dew point 25 °F - Altimeter: 29.96 inHg - Observed at: KSIY, 16 nm away - METAR: KSIY 072153Z AUTO 33007G17KT 10SM CLR 34/M04 A2996 RMK AO2 SLP128 T03441044= ## 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 20210707016999A](https://openairdocs.org/incident/20210707016999A), Jul 7, 2021: Bell 212, Substantial damage. A phone interview with pilot[privacy data omitted] July 17, 2021 by inspector [privacy data omitted] assistant to the iic revealed that [privacy data omitted]… ## Docket (26 files) The files NTSB released with the investigation on June 28, 2023, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=103465. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 2.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15384954&FileExtension=pdf&FileName=911KW%20accident%20report%209_21_21_Redacted-Rel.pdf - Memorandum for record - pilot interview with usfs (item 2, PDF, 3 pages, 113 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15424389&FileExtension=pdf&FileName=MEMORANDUM%20FOR%20RECORD%20-%20Pilot%20Interview%20with%20USFS-Rel.pdf - Accident photos (item 3, PDF, 3 pages, 1.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15431743&FileExtension=pdf&FileName=Accident%20Photos-Rel.pdf - Pilot training records external load (item 4, PDF, 5 pages, 16.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15431924&FileExtension=pdf&FileName=Pilot%20Training%20Records%20External%20Load_Redacted-Rel.pdf - Engine and airframe examination notes (item 5, PDF, 9 pages, 1.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15390572&FileExtension=pdf&FileName=WPR21LA268%20Examination%20Notes_Redacted-Rel.pdf - Memorandum for record - bucket examination (item 6, PDF, 1 page, 95 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15678571&FileExtension=pdf&FileName=MEMORANDUM%20FOR%20RECORD%20-%20FAA%20Bucket%20Inspection-Rel.pdf - Pylon mounts examination notes (item 7, PDF, 10 pages, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15434745&FileExtension=pdf&FileName=Transmission%20Mounts%20%26%20Friction%20Damper%20Examination%20Notes%20WPR21LA268-Rel.pdf - Pylon support examination notes comments (item 8, PDF, 2 pages, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15390293&FileExtension=pdf&FileName=Transmission%20Mounts%20%26%20Friction%20Damper%20Examination%20Comments%20via%20Email_Redacted-Rel.pdf - Memorandum for record - power pack engine exam summation (item 9, PDF, 3 pages, 200 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15549652&FileExtension=pdf&FileName=MEMORANDUM%20FOR%20RECORD%20-%20Engine%20Exam%20WPR21LA268%20PWC-Rel.pdf - Ipad examination narrative (item 10, PDF, 2 pages, 103 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15392968&FileExtension=pdf&FileName=iPad%20Exam%20Narrative%20MFR-Rel.pdf - Recorded air traffic control radar data (plot) (item 11, KMZ, 28 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15389879&FileExtension=kmz&FileName=12067_20210707233000_Once-Rel.kmz - Adsb data csv (item 12, CSV, 365 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15389754&FileExtension=csv&FileName=12067_20210707233000_Once-Rel.csv - Pylon support illustrated parts catalog excerpt (item 13, PDF, 1 page, 263 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15391064&FileExtension=pdf&FileName=212_PylonSupportInstallation-Rel.pdf - Pilot training records (item 14, PDF, 13 pages, 11.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15550132&FileExtension=pdf&FileName=Pilot%20Carding%20Documents,%20Benjamin%20Neel,%20Rogers%20Helicopters,%202021_Redacted-Rel.pdf - Maintenance due report (item 15, PDF, 13 pages, 417 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15432613&FileExtension=pdf&FileName=n911kw%20mx%20due%20report%2029jun21-Rel.pdf - Operator fire training manual excerpt (item 16, PDF, 3 pages, 196 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15431369&FileExtension=pdf&FileName=Operator%20Fire%20Training%20Manual%20Excerpt%20-%20Bambi%20Buckets-Rel.pdf - Hover gross weight performance chart excerpt (item 17, PDF, 1 page, 470 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15431864&FileExtension=pdf&FileName=Hover%20Gross%20Weight%20Performance%20Calculation%20Chart-Rel.pdf - Oge performance chart BHT-12-FMS-3 excerpt - takeoff power (item 18, PDF, 2 pages, 608 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15431874&FileExtension=pdf&FileName=OGE%20Performance%20Chart%20BHT-12-FMS-3%20Excerpt%20-%20Takeoff%20Power-Rel.pdf - Party form - manufacture (item 19, PDF, 1 page, 265 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15389764&FileExtension=pdf&FileName=Bell%20Party%20Form-Rel.pdf - Wreckage release form (item 20, PDF, 1 page, 67 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15424766&FileExtension=pdf&FileName=Wreckage%20Release%20Form%20N911KW_Redacted-Rel.pdf - Party representative form - usfs (item 21, PDF, 1 page): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15457283&FileExtension=pdf&FileName=CERTIFICATION%20OF%20PARTY%20REPRESENTATIVE%20USFS%20N911KW_Redacted-Rel.pdf - Evidence control form bambi bucket - 001 (item 22, PDF, 2 pages, 191 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15551195&FileExtension=pdf&FileName=Evidence%20Control%20Form%20Bucket%20Release%20WPR21LA268-Rel.pdf - Evidence control form - 002 (item 23, PDF, 2 pages, 329 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15427955&FileExtension=pdf&FileName=Evidence-Control-Form%20IPADs%20WPR21LA268%20N911KW-Rel.pdf - Evidence control form - 003 (item 24, PDF, 2 pages, 274 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15428714&FileExtension=pdf&FileName=Evidence-Control-Form%20N911KW%20mounts%20and%20dampers-Rel.pdf - Evidence control form - 004 (item 25, PDF, 2 pages, 337 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15550581&FileExtension=pdf&FileName=Evidence-Control-Form%20N911KW%20power%20pack-Rel.pdf - Evidence control form 005 (item 26, PDF, 2 pages, 139 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15456945&FileExtension=pdf&FileName=Evidence%20Control%20Form%20Logbooks%20%20WPR21LA268-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.