# NTSB ANC22LA007: Cessna 207A, N9794M, Bethel, AK, November 21, 2021 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: November 20, 2021, 17:55 local (Nov 21, 2021, 02:55 UTC) - Place: Bethel, AK - Coordinates: 60.779217, -161.8368 - Nearby events: https://openairdocs.org/map.md?lat=60.7792&lon=-161.8368&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Fire/smoke (non-impact)](https://openairdocs.org/ntsb-events/150) - Highest injury: No injuries - Injuries: 6 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Alaska Regional Office - Parties: Textron Aviation (Cessna), Federal Aviation Administration - NTSB case key (mKey): 104287 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC22LA007 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/104287/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=104287 - Page: https://openairdocs.org/ntsb/ANC22LA007 ## Probable cause The improper installation of an avionics wire harness over a fuel line, which resulted in chafing of the wire harness, arcing, and a subsequent fire. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Misc hardware: misc wiring](https://openairdocs.org/ntsb-findings/01071497): Aircraft › Fluids/misc hardware · Not serviced/maintained; cases with it: [Cessna 207A, 1 case](https://openairdocs.org/ntsb-findings/01071497/cases.md?model=2073605), [All aircraft, 3 cases](https://openairdocs.org/ntsb-findings/01071497/cases.md) - [Electrical power system: electrical pwr sys wiring](https://openairdocs.org/ntsb-findings/01022497): Aircraft › Aircraft systems · Fatigue/wear/corrosion (probable cause); cases with it: [Cessna 207A, 1 case](https://openairdocs.org/ntsb-findings/01022497/cases.md?model=2073605), [All aircraft, 44 cases](https://openairdocs.org/ntsb-findings/01022497/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-cruise: Fire/smoke (non-impact)](https://openairdocs.org/ntsb-events/150) (defining event); cases with it: [Cessna 207A, 1 case](https://openairdocs.org/ntsb-events/150/sequence.md?model=2073605), [All aircraft, 504 cases](https://openairdocs.org/ntsb-events/150/sequence.md) ## Analysis The pilot was conducting a scheduled air taxi flight with five passengers onboard. Shortly after departure, the pilot began to smell an electrical burn odor, and he elected to return to the airport. About 1 minute later, the electrical burn smell intensified, which was followed by visible smoke in the cockpit, and the pilot declared an emergency to the tower. After landing and all the passengers had safely departed the airplane, heavy smoke filled the cockpit and passenger compartment, and the pilot saw a candle-like flame just behind the pilot and co-pilot seats, just beneath the floorboards of the airplane. Moments later, the airplane was engulfed in flames. Postaccident examination of the airframe revealed the origin of the fire to be centered behind the pilot’s row of seats, where a wire harness was found improperly installed on top of the aft fuel line from the left tank. Examination of the wire harness found a range of thermal and electrical damage consistent with chafing from the fuel line. It is likely that the installation of the wire harness permitted contact with the fuel line, which resulted in chafing, arcing, and the subsequent fire. ## Factual narrative On November 20, 2021, about 1755 Alaska standard time, a Cessna 207 airplane, N9794M, sustained substantial damage when it was involved in an accident near Bethel, Alaska. The pilot and five passengers were not injured. The airplane was operated by Yute Commuter Service as a Title 14 Code of Federal Regulations Part 135 scheduled passenger flight. The purpose of the flight was to transport five passengers and cargo to Kwethluk, Alaska, which is located about 12 miles east of Bethel. The pilot reported that shortly after departure, he noticed that the red emergency locator transmitter (ELT) light on the instrument-panel-mounted remote switch had illuminated. The pilot then asked the Bethel tower operator if they were hearing an ELT signal, and the tower operator responded that no signal was being received. Moments later, the pilot began to smell an electrical burn smell and elected to return to Bethel. The pilot said that about 1 minute later, the electrical burn smell intensified, which was followed by visible smoke in the cockpit, and he then declared an emergency to the Bethel tower. The pilot then turned off the airplane’s master electrical switch, and subsequently opened his side window for ventilation and smoke removal. He said he briefly turned the master switch back on to again declare an emergency with Bethel tower, and to inform the tower operator that he was planning to land on runway 1L. The pilot said that during the landing roll, he realized that the nosewheel steering system and brake system were both inoperative. After the airplane rolled to a stop on the left side of runway 1L, he ordered all the passengers to evacuate the airplane. The pilot reported that after all the passengers had safely departed the airplane, heavy smoke filled the cockpit and passenger compartment, and he saw a candle-like flame behind the pilot and co-pilot seats, just beneath the floorboards of the airplane. Moments after all the passengers and pilot had exited the airplane, it was immediately engulfed in flames. See figure 1. Figure 1 Photo of accident airplane while still on Runway 1L. Examination of the maintenance records showed that on January 27, 2011, the Capstone system, phase 1, was installed on the accident airplane under Federal Aviation Administration (FAA) Supplemental Type Certificate (STC) number STC2154AK. The Capstone Program is a voluntary safety demonstration involving the installation, at FAA expense, of avionics suites in approximately 200 aircraft operated in western Alaska. The avionics suites, manufactured by UPS Aviation Technologies, consist of an MX-20 multifunction display (MFD), a GX-60 GPS nav/com, a Universal Access Transceiver (UAT), and an installation kit with all necessary cables, antennas, and mounting hardware, and an instruction book. A National Transportation Safety Board (NTSB) postaccident examination of the airplane wreckage revealed the origin of the fire to be centered behind the pilot’s row of seats, where awire harness, which was discovered to be part of the Capstone Program equipment, was found improperly installed on top of the aft fuel line from the left fuel tank. The fuel line exhibited chafing and thermal damage. Following removal of the fuel line, a small pinhole was detected in the fuel line utilizing a flashlight. NTSB Materials Laboratory examination of the wire harness found a range of thermal and electrical damage, from thermal discoloration and sooting to beading and welding in areas on individual conductors. The damage was consistent with the wire being energized at the time the damage occurred. During the on-scene NTSB examination of the accident airplane wreckage, a second Cessna 207, which was purchased at the same time as the accident airplane, was examined in the operator’s hangar. The NTSB IIC, along with the entire investigative team, discovered that the same Capstone wire harness condition found in the accident airplane existed in the second Cessna 207 in the same location. As a result of the NTSB investigation, the FAA issued a notification letter to alert registered aircraft owners and operators of the need to inspect the area inside inspection panels from the rear door frame forward under the pilots and passengers’ floorboards at the next maintenance function, 100 hour, or Annual inspections. FAA database records indicate there is over 200 aircraft that had the CAPSTONE phase 1 equipment installation under STC2154AK and therefore need to be inspected. ## Aircraft - Registration: [N9794M](https://openairdocs.org/aircraft/N9794M), registered now, S/N 20700730, built 1981 (OpenAirDocs) - Reported make and model: CESSNA 207A - Registry model: [Cessna 207A](https://openairdocs.org/model/cessna-207a) (registry code 2073604) (OpenAirDocs) - Registry engine: [Continental IO-520-F](https://openairdocs.org/engine/continental-io-520-f) (registry code 17237, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 20700730 - Year built: 1981 - Airframe hours: 15727.9 - Engines: CONT MOTOR IO-520-R 300 horsepower reciprocating - Damage: Substantial damage - Fire: Both - Flight: Business, Part 135 - Operator: Paklook Air Inc, doing business as Yute Commuter Service - Registered owner: Yr-Aircraft Leasing LLC - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, November 13, 2021 - Destination: Same as departure - Flight plan: Company VFR - Airport: BET, Bethel, runway 1L, 6,400 × 150 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 28; injuries: none; flight instructor, commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review March 30, 2021; seat: left; restraint: 3-point; flight hours: 1,480 total, 659 in this make and model, 1,128 as pilot in command, 293 in the last 90 days, 128 in the last 30 days, 7 in the last 24 hours ## Weather - Conditions: Visual (VMC), Dusk - Wind: 10° at 16 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: -0 °F, dew point -8 °F - Altimeter: 29.92 inHg - Observed at: PABE - METAR: PABE 210253Z 01016KT 10SM CLR M18/M22 A2992 RMK AO2 SLP136 T11831217 56003 $ ## 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 20211120016929A](https://openairdocs.org/incident/20211120016929A), Nov 20, 2021: Cessna 207A, Bethel, AK, Substantial damage. On November 20, 2021 at approximately 1800 Alaska time, Cessna C-207A N9794M incurred substancial damage in a post landing fire. All 5 passenger including the… ## Other investigations on N9794M (1) 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. - [NTSB ANC01LA099](https://openairdocs.org/ntsb/ANC01LA099), Aug 3, 2001: Cessna 207 (N9794M), Healy, AK, substantial damage. Probable cause: The pilot's continued flight into adverse weather conditions after becoming lost/disoriented. Factors in the accident were rising terrain, a blind/box canyon, low clouds, and rain. ## Docket (7 files) The files NTSB released with the investigation on September 20, 2023, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=104287. 11.2 MB in all. - Materials laboratory factual report (item 1, PDF, 5 pages, 1.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14202835&FileExtension=pdf&FileName=22-036%20Factual-Rel.pdf - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 2, PDF, 9 pages, 3.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14202624&FileExtension=pdf&FileName=ANC22LA007%206120%20redacted-Rel.pdf - Wreckage examination (item 3, PDF, 14 pages, 1.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16089440&FileExtension=pdf&FileName=ANC22LA007%20Wreckage%20examintion-Rel.pdf - FAA notification letter for wiring issue STC2154AK (item 4, PDF, 3 pages, 894 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15965817&FileExtension=pdf&FileName=FAA%20Notification%20Letter%20for%20Wiring%20Issue%20STC2154AK-Rel.pdf - Statement of party representatives to NTSB investigation (item 5, PDF, 3 pages, 3.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15260280&FileExtension=pdf&FileName=ANC22LA007%20Party%20Rep%20forms-Rel.pdf - Release of aircraft wreckage, NTSB form 6120.15 (item 6, PDF, 2 pages, 23 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15160195&FileExtension=pdf&FileName=ANC22LA007%20Wreckage%20Release%20Form_Redacted-Rel.pdf - Investigative photographs (item 7, PDF, 3 pages, 901 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13768557&FileExtension=pdf&FileName=Photo%20Array%20ANC22LA007%20BET-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.