# NTSB CEN21LA274: Beech U-8F, N62069, Goodland, KS, June 17, 2021 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Class 3 · Limited · Final report - Date: June 16, 2021, 19:05 local (Jun 17, 2021, 01:05 UTC) - Place: Goodland, KS · Ramp - Coordinates: 39.370627, -101.69898 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=39.3706&lon=-101.6990&mi=10 - Phase of flight: [Standing](https://openairdocs.org/ntsb-phases/150) (OpenAirDocs' grouping) - Defining event: [Standing-engine(s) start-up: Explosion (non-impact)](https://openairdocs.org/ntsb-events/160) - Highest injury: Minor injuries - Injuries: 1 minor - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Central Region - Parties: Flight Standards District Office, Textron Aviation, Bemidji Aviation - NTSB case key (mKey): 103280 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN21LA274 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/103280/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=103280 - Page: https://openairdocs.org/ntsb/CEN21LA274 ## Probable cause Maintenance personnel’s inadequate inspection of the airplane, which failed to detect and correct chafed electrical wiring and a degraded fuel bladder with holes, which resulted in ignition of fuel vapor and a right wing explosion. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Inspection: scheduled/routine inspection](https://openairdocs.org/ntsb-findings/02061520): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Beech U-8F, 1 case](https://openairdocs.org/ntsb-findings/02061520/cases.md?model=1152801), [All aircraft, 167 cases](https://openairdocs.org/ntsb-findings/02061520/cases.md) - [Policy/procedure: adequacy of policy/proc](https://openairdocs.org/ntsb-findings/04021015): Organizational issues › Management · Maintenance provider; cases with it: [Beech U-8F, 1 case](https://openairdocs.org/ntsb-findings/04021015/cases.md?model=1152801), [All aircraft, 106 cases](https://openairdocs.org/ntsb-findings/04021015/cases.md) - [Fuel system: fuel sys wiring](https://openairdocs.org/ntsb-findings/01022897): Aircraft › Aircraft systems · Inadequate inspection (probable cause); cases with it: [Beech U-8F, 1 case](https://openairdocs.org/ntsb-findings/01022897/cases.md?model=1152801), [All aircraft, 5 cases](https://openairdocs.org/ntsb-findings/01022897/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Standing-engine(s) start-up: Explosion (non-impact)](https://openairdocs.org/ntsb-events/160) (defining event); cases with it: [Beech U-8F, 2 cases](https://openairdocs.org/ntsb-events/160/sequence.md?model=1152801), [All aircraft, 20 cases](https://openairdocs.org/ntsb-events/160/sequence.md) ## Analysis The pilot heard a loud bang while starting the right engine and noticed flames exiting the right wing. An airport surveillance camera captured a wing explosion that lasted about 1 second, which substantially damaged the right wing. Examination revealed that the right wing outboard aft fuel bladder was brittle, with several holes due to age-related oxidation, and electrical wiring to the navigation lights was chafed in two locations, with evidence of electrical arcing. Review of maintenance records indicated that the airplane was inspected about 50 hours before the accident; the inspection included checking the fuel tanks for leakage, and electrical wiring for chafing. Based on the condition of the fuel bladder and wiring, it is likely that the most recent inspection was inadequate. About 2 years before the accident, the airplane’s left wing exploded due to ignition of fuel vapor. Following the most recent wing explosion accident, the operator instituted several maintenance protocols to aid in detection of a fuel leak, including top-off of the fuel system in conjunction with the wing inspection procedure checklist or unscheduled fuel system maintenance. ## Factual narrative On June 16, 2021, at 1905 mountain daylight time, a Beech U-8F airplane, N62069, was substantially damaged when it was involved in an accident near Goodland, Kansas. The pilot sustained minor injuries. The airplane was operated by Bemidji Aviation Services Inc. as a Title 14 Code of Federal Regulations Part 135 cargo flight. The pilot stated that, while starting the right engine, he heard a loud bang and noticed flames coming out of the right wing. An airport surveillance video captured flames from the right wing for about 1 second. The pilot shut down the right engine with the mixture control and egressed the airplane. Examination revealed that the outboard 12 ft of the right wing was heavily damaged, with the forward spar deflected significantly aft and the right-wing leading edge curled aft. The outboard aft fuel bladder for the right wing was removed and observed to be in a degraded condition, with indications of fire damage. Electrical wiring to the navigation light was chafed and conductor was exposed in two locations. The outboard aft fuel bladder and wiring bundle from the right wing were both submitted to the National Transportation Safety Board Materials Laboratory for examination. The fuel bladder was constructed of nitrile butadiene rubber and was brittle in several areas, with multiple holes. A sample from the edge of one of the holes examined using a Fourier Transform Infrared spectrometer indicated degradation due to oxidation, with the embrittlement consistent with physical aging of the bladder material. The right wing wire bundle contained several areas where the insulation for the wires was chafed. One chafed area of the wiring for the navigation lights showed evidence of electrical arcing and welding. Electrical damage to the conductor surface indicated that the wire was energized at the time the damage occurred. The operator maintained the airplane with a maintenance manual accepted by the Federal Aviation Administration. The manual contained a continuous care inspection guide that required a routine inspection of the entire airplane every 60 flight hours, as well as eight more detailed inspections of specific portions of the airplane every 480 flight hours. On May 22, 2021, about 50 flight hours before the accident, a detailed inspection occurred that required following areas be checked: 1) Fuel Tanks, Vents, and Pumps – Check cells for leaks, plugged vents, pumps for leakage. 2) Fuel Caps and O-Rings – Check fuel caps and O-rings for fit and seal. 3) Fuel Quantity Transmitters – Check for leakage or visible damage. 4) Plumbing – Check for chaffing, leakage and damage, and proper attachment. 5) Electrical Wiring and Equipment – Check for security, chaffing damage and attachment. On July 9, 2019, the airplane was involved in a similar accident that the NTSB investigation attributed to an explosion of the outboard left wing due to electrical arcing and ignition of fuel vapors. Following the most recent wing explosion accident,the operator instituted several maintenance protocols to aid in detection of a fuel leak, including top-off of the fuel system in conjunction with the wing inspection procedure checklist or unscheduled fuel system maintenance. ## Aircraft - Registration: [N62069](https://openairdocs.org/aircraft/N62069), registered now, S/N 62-3866 (OpenAirDocs) - Reported make and model: BEECH U-8F - Registry model: [Beech U-8F](https://openairdocs.org/model/beech-u-8f) (registry code 1152801) (OpenAirDocs) - Category: Airplane - Serial number: 62-3866 - Year built: 1962 - Airframe hours: 9624 - Engines: Lycoming IO-720-A1B 400 horsepower reciprocating; Lycoming IO-720-A1B 400 horsepower reciprocating - Damage: Substantial damage - Flight: Business, Part 135 - Operator: Bemidji Aviation Services Inc - Registered owner: Bemidji Aviation Services Inc - Airworthiness certificate: Standard, Normal - Last inspection: Continuous airworthiness, May 20, 2021, 50 hours before - Departed: GLD, Goodland, KS - Destination: DEN, Denver, CO - Flight plan: IFR - Airport: GLD, Renner Fld /Goodland Muni/ ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 20; injuries: minor; commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, without waivers/limitations; last flight review May 28, 2021; seat: left; restraint: 4-point; flight hours: 2,210 total, 477 in this make and model, 2,096 as pilot in command, 164 in the last 90 days, 59 in the last 30 days, 3 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 190° at 6 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 88 °F, dew point 52 °F - Altimeter: 30.01 inHg - Observed at: KGLD - METAR: KGLD 170053Z AUTO 19006KT 10SM CLR 31/11 A3001 ## 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 20210617013169A](https://openairdocs.org/incident/20210617013169A), Jun 17, 2021: Beech U-8F, Goodland, KS, Substantial damage. Pilot statement: I started up the right engine and as I began to lean the mixture to stabilize the engine I heard a loud bang from the area of the right wing.… ## Other investigations on N62069 (2) 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 CEN19LA215](https://openairdocs.org/ntsb/CEN19LA215), Jul 9, 2019: Beech 65 (N62069), Sidney, NE, substantial damage. Probable cause: The improper maintenance of the outboard left wing, which allowed electrical arcing and leaking of the fuel sending unit and subsequently resulted in ignition of fuel vapors and an explosion of the… - [NTSB CEN19LA086](https://openairdocs.org/ntsb/CEN19LA086), Feb 22, 2019: Beech 65 (N62069), Colby, KS, substantial damage. Probable cause: The pilot’s failure to properly secure the crew hatch door before takeoff, which resulted in his distraction and his failure to maintain airplane control and airspeed. ## Docket (9 files) The files NTSB released with the investigation on August 25, 2022, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=103280. 194 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 10 pages, 2.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14156059&FileExtension=pdf&FileName=6120_Redacted-Rel.pdf - Video of explosion from airport surveillance (item 2, AVI, 2.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14022685&FileExtension=avi&FileName=Airport%20video-Rel.avi - Video of explosion from airport surveillance - 400% zoom at 10% speed (item 3, MP4, 185 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14022570&FileExtension=mp4&FileName=Airport%20video%20-%20400%25%20Zoom%2010%25%20Speed-Rel.mp4 - Photos of airplane (item 4, PDF, 2 pages, 197 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14032475&FileExtension=pdf&FileName=Photos-Rel.pdf - NTSB maintenance records review - factual report (item 5, PDF, 18 pages, 309 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12932262&FileExtension=pdf&FileName=Maintenance%20Factual-Rel.pdf - NTSB exam of fuel bladder and wiring bundle - factual report (item 6, PDF, 7 pages, 2.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14022284&FileExtension=pdf&FileName=Bladder%20and%20Wiring%20-%20Factual%20Report%20-%20CEN21LA274-Rel.pdf - Similar accident of the airplane - NTSB accident report (item 7, PDF, 6 pages, 151 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14032233&FileExtension=pdf&FileName=Similar%20Accident%20of%20Airplane-Rel.pdf - Operator initiatives following accident (item 8, PDF, 1 page, 152 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14142975&FileExtension=pdf&FileName=Follow%20up%20initiatives-Rel.pdf - Statement of party representatives to NTSB investigation (item 9, PDF, 2 pages, 774 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14022552&FileExtension=pdf&FileName=Party%20Statements%20-%20combined%20-%20redacted-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.