# NTSB WPR11FA348: Cessna 210-5(205), N8427Z, Darby, MT, July 22, 2011 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Field investigation · Final report - Date: July 22, 2011, 12:25 local (18:25 UTC) - Place: Darby, MT - Coordinates: 45.883335, -114.199996 - Nearby events: https://openairdocs.org/map.md?lat=45.8833&lon=-114.2000&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) - Highest injury: Minor injuries - Injuries: 2 minor - Status: Completed, report November 7, 2012 - Report: Approved by Office Director - NTSB office: Western Pacific Region - Parties: FAA FSDO - NTSB case key (mKey): 81223 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR11FA348 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/81223/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=81223 - Page: https://openairdocs.org/ntsb/WPR11FA348 ## Probable cause The fatigue failure of the aluminum air intake duct, which resulted in material being ingested into the engine cylinders and a subsequent loss of engine power during cruise flight. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Power plant: air intake](https://openairdocs.org/ntsb-findings/01057160): Aircraft › Aircraft power plant · Fatigue/wear/corrosion (probable cause); cases with it: [Cessna 210-5(205), 1 case](https://openairdocs.org/ntsb-findings/01057160/cases.md?model=2073202), [All aircraft, 50 cases](https://openairdocs.org/ntsb-findings/01057160/cases.md) - [Aircraft](https://openairdocs.org/ntsb-findings/01050000): Aircraft › Aircraft power plant · Failure (probable cause); cases with it: [Cessna 210-5(205), 1 case](https://openairdocs.org/ntsb-findings/01050000/cases.md?model=2073202), [All aircraft, 151 cases](https://openairdocs.org/ntsb-findings/01050000/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-cruise: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event); cases with it: [Cessna 210-5(205), 4 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=2073202), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) - [Emergency descent: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Cessna 210-5(205), 4 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=2073202), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) - [Landing-landing roll: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Cessna 210-5(205), 6 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=2073202), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The pilot reported that, while in a cruise flight, the engine began to run rough and eventually lost power. The pilot subsequently initiated a forced landing to a gravel road, and the airplane collided with a tree during the landing roll. Postaccident examination of the engine found a 4-inch by 2-inch hole and material loss on the bottom side of the aluminum air intake duct assembly. The circumference of the hole was an irregular shape with both jagged and smooth edges/fracture surfaces. The fractures were consistent with fatigue and were possibly the result of vibration. Internal borescope examination of the cylinders revealed mechanical etching to the No. 4 and No. 6 combustion chambers and associated valve heads. The corresponding spark plugs were removed and mechanical damage was noted. The ground electrodes were bent down onto the insulators and center electrodes. No other mechanical failures were noted with the engine or airframe. It is likely that the missing aluminum duct material was ingested into the cylinders, which resulted in a loss of engine power. Although there was evidence that a weld repair had been performed on the air intake duct near the area of the hole, it could not be determined if it contributed to the hole and loss of material. A review of the airplane’s maintenance records showed no recent modifications or repairs to the engine air intake duct. ## Factual narrative HISTORY OF FLIGHT On July 22, 2011, at 1225 mountain daylight time, a Cessna 210-5, N8427Z, sustained substantial damage following a loss of engine power and subsequent forced landing near Darby, Montana. The airplane was registered to the pilot and operated under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The commercial pilot and passenger sustained minor injuries. The flight departed Lemhi County Airport, Salmon, Idaho, at 1155, with a planned destination of Chamberlin, Idaho. Visual meteorological conditions (VMC) prevailed and no flight plan was filed for the cross-country flight. The pilot reported that the airplane was in a cruise flight configuration when the engine began to run rough and eventually lost power. The pilot maneuvered the airplane towards a nearby open valley and gravel road. The pilot positioned the airplane to land downwind to the road and prepared for a short/soft field landing. He reported that the airplane touched down on the gravel road about 200 feet beyond a cattle guard and began to skid. The pilot reduced braking pressure and crossed a second cattle guard. During the landing rollout, the airplane's left wing impacted a tree and the airplane pivoted approximately 90-degrees to the left before it came to an abrupt stop. The airplane sustained substantial damage to the left wing and forward fuselage. AIRCRAFT INFORMATION The accident airplane (serial number 205-0427) was manufactured in 1963. The single engine airplane was equipped with a Continental IO-470 S engine and constant-speed propeller manufactured by McCauley. The most recent annual inspection of the airplane, engine, and propeller was completed on January 9, 2011. At the time of the accident, the airplane had accumulated 7,343 total hours and the engine had accumulated 475 total hours since new. The airplane had accumulated approximately 56 hours between the annual inspection and the accident. TESTS AND RESEARCH The NTSB conducted a postaccident examination of the engine and airframe after the airplane was transported to a storage facility in Phoenix, Arizona. The examination revealed a dark residue that covered the left side of the engine accessory section (aft) and associated baffling and hoses. The residue was concentrated in the area of the outboard engine air intake duct assembly, just aft of the bracket air filter. The air filter, bracket assembly and aluminum air intake duct were removed. A large hole (approximately 4.25 inches by 1.75 inches) and material loss was noted on the bottom side of the duct. The circumference of the hole was an irregular shape with both jagged and smooth edges/fracture surfaces. A dark residue was noted to the face of the fracture surfaces. A weld repair was noted adjacent to the hole. A section of fuel pump baffle tubing was routed adjacent to the hole in the outboard intake duct. Rub marks and dark residue was noted along the baffle tubing, concentrated in the area of the hole in the duct. Materialloss and deformation was noted to the baffle tubing in the area adjacent to the hole in the intake duct. Internal borescope examination of the piston cylinders revealed mechanical etching to the No. 4 and No. 6 combustion chambers and associated valve heads. The corresponding spark plugs were removed and mechanical damage was noted. The ground electrodes were bent down onto the insulators and center electrodes. The examination of the airframe and engine revealed no additional findings or anomalies. Additional examination notes are located in the public docket associated with this case file. A senior NTSB metallurgist examined the engine air intake duct and reported that the fractures were consistent with fatigue and possibly the result of vibration. Although there was evidence that a weld repair had been performed near this area, it was not determined if it contributed to the hole and loss of material. A review of the airplane’s maintenance records showed no recent modifications or repairs to the engine air intake duct. ## Aircraft - Registration: [N8427Z](https://openairdocs.org/deregistered/N8427Z-2014-03-11), registration cancelled 2014-03-11, S/N 205-0427, built 1963 (OpenAirDocs) - Reported make and model: CESSNA 210-5(205) - Registry model: [Cessna 210-5(205)](https://openairdocs.org/model/cessna-210-5-205) (registry code 2073202) (OpenAirDocs) - Registry engine: [Continental I0-470 series](https://openairdocs.org/engine/continental-i0-470-series) (registry code 17027, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 205-0427 - Airframe hours: 7343 - Engines: CONT MOTOR IO-470 SERIES 260 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: Finkle Richard G - Registered owner: Finkle Richard G - Airworthiness certificate: Standard, Normal - Last inspection: Annual, January 1, 2011, 56 hours before - Departed: KSMN, Salmon, ID - Destination: U79, Chamberlain, ID ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 66; injuries: minor; commercial; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 3, without waivers/limitations; last flight review August 5, 2010; seat: left; flight hours: 7,521 total, 7,107 in this make and model, 7,107 as pilot in command, 70 in the last 90 days, 17 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 340° at 3 knots - Visibility: 75 statute miles - Lowest ceiling: none - Temperature: 75 °F, dew point 48 °F ## 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 20110722015599A](https://openairdocs.org/incident/20110722015599A), Jul 22, 2011: Cessna 210-5(205), Darby, MT, Substantial damage. On July 22, 2011, at 1225 MDT, a Cessna 210-5, N8427Z, registered to [privacy data omitted], struck a tree while executing a forced landing approximately 25… ## Docket (4 files) The files NTSB released with the investigation on July 31, 2012, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=81223. 5.1 MB in all. - Materials Laboratory 15 - Factual Report 12-059 (7 embedded images) (item 1, .PDF, 7 photos, 1.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40371599&FileExtension=.PDF&FileName=Materials%20Laboratory%2015%20-%20Factual%20Report%2012-059%20(7%20embedded%20images)-Master.PDF - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 2, .PDF, 1.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40370281&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Airframe and Engine Examination Report (9 Embedded Photos) (item 3, .PDF, 9 photos, 2.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40370413&FileExtension=.PDF&FileName=Airframe%20and%20Engine%20Examination%20Report%20(9%20Embedded%20Photos)-Master.PDF - Statement of Party Representatives to NTSB Investigation (item 4, .PDF, 65 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40372475&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Redacted.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.