# NTSB ANC21FA015: Cessna 185, N9725Z, Chitina, AK, February 4, 2021 - Type: NTSB accident investigation - Classification: Accident · Fatal · Class 3 · Field · Final report - Date: February 4, 2021, 10:51 local (19:51 UTC) - Place: Chitina, AK - Coordinates: 61.584722, -144.04583 - Nearby events: https://openairdocs.org/map.md?lat=61.5847&lon=-144.0458&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Aircraft structural failure](https://openairdocs.org/ntsb-events/337) - Highest injury: Fatal - Injuries: 2 fatal - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Alaska Regional Office - Parties: Copper Valley Air Service, Federal Aviation Administration, Cessna / Textron Aircraft - NTSB case key (mKey): 102605 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC21FA015 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/102605/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=102605 - Page: https://openairdocs.org/ntsb/ANC21FA015 ## Probable cause An in-flight breakup during cruise flight for reasons that could not be determined based on available evidence. ## 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: [Cessna A185E, 2 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md?model=2072818), [All aircraft, 2,247 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-cruise: Aircraft structural failure](https://openairdocs.org/ntsb-events/337) (defining event); cases with it: [Cessna A185E, 1 case](https://openairdocs.org/ntsb-events/337/sequence.md?model=2072818), [All aircraft, 290 cases](https://openairdocs.org/ntsb-events/337/sequence.md) ## Analysis The pilot was conducting a scheduled passenger flight in the single-engine airplane in day visual meteorological conditions. Recovered data from an onboard GPS unit revealed that, after reaching a GPS altitude of about 7,500 ft, the airplane flew on a southeast track for about 10 minutes with a groundspeed between 120 and 130 knots. About 2 minutes before the accident, the airplane initiated a gradual right turn to the south and began a descent that averaged about 734 ft per minute. The last fully recorded in-flight data point showed the airplane at a GPS altitude of 5,715 ft with a groundspeed of 154 kts. The distribution of the wreckage at the accident site indicated a high-speed, near vertical impact, with portions of the right wing and empennage scattered between 400 and 700 ft from the main wreckage, consistent with an in-flight breakup. Fractured areas of the right wing, the left deformation of the vertical stabilizer and rudder, and the fractured attach points were consistent with overload separation of the right wing, which caused the airplane to snap roll to the right, creating the necessary torsional forces to deform the vertical stabilizer and twist the empennage from the fuselage. Examinations on the engine and airframe did not reveal evidence of any pre-existing anomalies that would have precluded normal operation. Flight control continuity was established, and the propeller showed evidence of rotation at impact. All of the fractured surfaces exhibited a dull, grainy appearance consistent with overstress separation. There was no evidence of fatigue or corrosion noted on any of the areas examined. The reason for the overstress and subsequent in-flight breakup could not be determined based on the available information. ## Factual narrative The accident airplane was involved in a collision in May 2014 that damaged the right wing, vertical stabilizer, rudder, right horizontal stabilizer, and right elevator. The right wing was replaced with a wing from a Cessna 180H. The differences between the Cessna 180H wing and the Cessna A185E wing are not structurally significant. Some repairs were performed to the outboard upper skin and ribs of the replacement right wing. The vertical stabilizer, rudder, right horizontal stabilizer, and right elevator were repaired. On February 4, 2021, about 1051 Alaska standard time, a Cessna A185E, N9725Z, sustained substantial damage when it was involved in an accident about 14 miles northeast of Chitina, Alaska. The commercial pilot and passenger were fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 135 scheduled passenger flight. A Garmin 696 GPSMAP was recovered from the accident site. GPS data logs for the day of the accident revealed that, after reaching a GPS altitude of about 7,500 ft, the airplane continued on a southeasterly track for about 10 minutes with a groundspeed between 120 and 130 knots. About 2 minutes before the accident, the airplane initiated a gradual right turn to the south and began a descent, which averaged about 734 ft per minute. The last fully recorded in-flight data point was at 1050:52, when the airplane was at a GPS altitude of 5,715 ft with a groundspeed of 154 kts and on a track of 282° (see figure 1). Figure 1. Flight track Two pilots that responded to the accident site shortly after the accident reported no turbulence or significant winds aloft from the surface to 5,500 ft msl. The wreckage was scattered over mountainous, wooded terrain northeast of Chitina on the north side of the Chitina River Valley. The main wreckage included both landing gear with wheel penetration skis, engine, firewall, main fuselage, instrument panel, and left wing. The right wing, right aileron, right lift strut, and empennage were not found with the main wreckage. The part (top skin of right wing) located farthest from the main wreckage was about 710 ft from the main wreckage; the empennage was located about 446 ft from the main wreckage; and the inboard portion of the right wing was located about 407 ft from the main wreckage. The debris path and separated sections of the right wing and empennage were consistent with an in-flight breakup (see figure 2). Figure 2. Debris field Examination of the main wreckage revealed evidence consistent with the airplane impacting the ground in a high-speed, near-vertical descent. The lower end of the left-wing strut was separated from the fuselage. The left-wing strut bolt was intact in the fitting and the fuselage lugs were fractured through the hole. The left wing remained attached at the fuselage attach points and exhibited compressive buckling on the inboard portion of the wing consistent with impact damage and the left wing being fully attached and intact beforeground impact. The skis remained attached to their respective attach points and all ski arresting cables, bungees, and rigging were intact and attached at their respective attach points. No preimpact mechanical anomalies were noted with the skis or their rigging. All airframe parts were located within the main wreckage and surrounding woods. Flight control continuity was confirmed to all flight control surfaces except where recovery and overload separations existed. Both right-wing attach points exhibited damage and deformation in an upward direction at the wing root, consistent with a positive overload separation of the right wing before ground impact. The right-wing strut separated from the lower strut fitting with the rivets showing shear overstress signatures consistent with positive overload. The left deformation of the vertical stabilizer and rudder and the fractured attach points were consistent with the right wing failing first. Cable tears in the left fuselage and right empennage were consistent with the tail departing to the left side. All of the fracture surfaces examined had a dull, grainy appearance consistent with overstress separation. There was no evidence of corrosion or fatigue noted on any of the areas examined. The two-bladed, constant speed propeller remained attached to the crankshaft flange; however, the crankshaft was fractured behind the crankshaft flange near the front of the engine case. The fractured surface had an angular, dull, grainy appearance consistent with overstress separation. One of the propeller blades was slightly bent aft and rotated freely in the hub. The other propeller blade was bent aft about 180° with minor leading-edge chunking, chordwise scratching, and gouging on the cambered face. Examination of the engine did not reveal evidence of any preimpact anomalies that would have precluded normal operation. ## Aircraft - Registration: [N9725Z](https://openairdocs.org/deregistered/N9725Z-2022-02-25), registration cancelled 2022-02-25, S/N 185-1035, built 1966 (OpenAirDocs) - Reported make and model: CESSNA 185 (E) - Registry model: [Cessna A185E](https://openairdocs.org/model/cessna-a185e) (registry code 2072818) (OpenAirDocs) - Registry engine: [Continental IO-520 series](https://openairdocs.org/engine/continental-io-520-series) (registry code 17032, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 185-1035 - Year built: 1966 - Airframe hours: 6569.75 - Engines: Continental IO-520-D 300 horsepower reciprocating - Damage: Substantial damage - Flight: Business, Part 135 - Operator: Copper Valley Air Service - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, November 6, 2020 - Departed: PAGK, Glennallen, AK - Destination: PMXY, McCarthy, AK - Flight plan: Company VFR - Equipment: Handheld GPS, Satellite tracking device, Stall warning system ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 46; injuries: fatal; commercial; airplane ratings: multi-engine land, single-engine sea, single-engine land; instrument ratings: airplane; medical: class 2, without waivers/limitations; last flight review June 22, 2020; seat: left; restraint: 4-point; toxicology performed; flight hours: 2,883 as pilot in command, 62 in the last 90 days, 19 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 10 statute miles - Temperature: -8 °F, dew point -15 °F - Altimeter: 30.26 inHg - Observed at: PAGK, 53 nm away - METAR: PAGK 042153Z AUTO 00000KT 10SM CLR M22/M26 A3026 RMK AO2 SLP329 T12221256 TSNO ## 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 20210204001379A](https://openairdocs.org/incident/20210204001379A), Feb 4, 2021: Cessna A185E, Chitna, AK, Destroyed, 2 fatal. Aircraft sustained an inflight breakup due to unknown reasons while enroute from pagk to pamx. The cause for the inflight breakup is still under investigation. ## Docket (11 files) The files NTSB released with the investigation on April 26, 2022, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=102605. 23.3 MB in all. - Structures group chairman's factual report (item 1, PDF, 9 pages, 9 photos, 1.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13089828&FileExtension=pdf&FileName=ANC21FA015%20Structures%20Factual-Rel.pdf - Structures group chairman's factual report appendix a-maintenance records (item 2, PDF, 28 pages, 14 photos, 12.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13089848&FileExtension=pdf&FileName=ANC21FA015%20Structures%20Appendix%20A-Mx%20Records_Redacted-Rel.pdf - Global positioning system device - specialist's factual report (item 3, PDF, 5 pages, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13132132&FileExtension=pdf&FileName=ANC21FA015_G696_Factual-Rel.pdf - Global positioning system device - specialist's factual report - attachment 1 (item 4, CSV, 4 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13130674&FileExtension=csv&FileName=ANC21FA015_G696_Factual_Attachment_1-Rel.csv - Personal electron devices report (item 5, PDF, 4 pages, 1.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13229333&FileExtension=pdf&FileName=Photo%20PED%20report-Rel.pdf - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 6, PDF, 9 pages, 3.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13064333&FileExtension=pdf&FileName=N9725Z%20NTSB%206120_Redacted-Rel.pdf - Witness statements (item 7, PDF, 2 pages, 133 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13064547&FileExtension=pdf&FileName=Witness%20Statements-Rel.pdf - Wreckage examination summary (item 8, PDF, 3 pages, 285 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13076203&FileExtension=pdf&FileName=ANC21FA015%20Wreckage%20Examination%20Summary-Rel.pdf - Memorandum for record a�� medical and pathological information (item 9, PDF, 1 page, 116 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13084674&FileExtension=pdf&FileName=Autopsy%20Memo%20for%20Record-Rel.pdf - Toxicological report (item 10, PDF, 1 page, 167 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13222533&FileExtension=pdf&FileName=Tox%20dms_Redacted-Rel.pdf - Photos (item 11, PDF, 4 pages, 2.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13752356&FileExtension=pdf&FileName=Photo%20Array%20DMS-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.