# NTSB ANC09LA086: Cessna 180, N4601A, Chugiak, AK, August 25, 2009 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: August 24, 2009, 17:20 local (Aug 25, 2009, 01:20 UTC) - Place: Chugiak, AK - Coordinates: 61.456665, -149.370285 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=61.4567&lon=-149.3703&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) - Highest injury: Minor injuries - Injuries: 4 minor - Status: Completed, report May 28, 2010 - Report: Approved by Office Director - NTSB office: Alaska Regional Office - Parties: Federal Aviation Administration (Airworthiness) - NTSB case key (mKey): 74585 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC09LA086 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/74585/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=74585 - Page: https://openairdocs.org/ntsb/ANC09LA086 ## Probable cause The pilot’s delayed use of carburetor heat while operating in conditions conducive to carburetor icing. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine controls](https://openairdocs.org/ntsb-findings/01057600): Aircraft › Aircraft power plant · Not used/operated (probable cause); cases with it: [Cessna 180, 1 case](https://openairdocs.org/ntsb-findings/01057600/cases.md?model=2072602), [All aircraft, 51 cases](https://openairdocs.org/ntsb-findings/01057600/cases.md) - [Action: delayed action](https://openairdocs.org/ntsb-findings/02041025): Personnel issues › Action/decision · Pilot (probable cause); cases with it: [Cessna 180, 4 cases](https://openairdocs.org/ntsb-findings/02041025/cases.md?model=2072602), [All aircraft, 894 cases](https://openairdocs.org/ntsb-findings/02041025/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event); cases with it: [Cessna 180, 9 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=2072602), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) - [Emergency descent: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Cessna 180, 54 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=2072602), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The airline transport pilot reported that he was approaching his destination airport at the conclusion of a local personal flight. He said that while in cruise flight at 1,200 feet above ground level, the engine began to run rough and lose power. He noticed that the carburetor air temperature was just above the carburetor ice zone marked in red on the gauge, so he applied full carburetor heat, which was followed by a complete loss of engine power. Unable to restart the engine, he selected a marshy tree-covered site as a forced landing area. The airplane sustained substantial damage to the fuselage and wings during the forced landing. A Federal Aviation Administration airworthiness inspector’s postaccident inspection disclosed no evidence any preimpact mechanical problems. An aviation weather reporting station indicated that the temperature was 57 degrees F, and the dew point was 45 degrees F. When these values are entered into a carburetor icing probability chart, the results are in the "serious icing-cruise power" category. Given the lack of any mechanical anomalies it is likely that the formation of carburetor ice resulted in the loss of engine power. ## Factual narrative On August 24, 2009, about 1720 Alaska daylight time, a wheel-equipped Cessna 180 airplane, N4601A, sustained substantial damage during a forced landing, about 5 miles northeast of the Birchwood Airport, Chugiak, Alaska. The airplane was being operated as a visual flight rules (VFR) personal flight under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91, when the accident occurred. The airline transport pilot and three passengers all sustained minor injuries. Visual meteorological conditions prevailed, and no flight plan was filed. The flight originated at the Birchwood Airport, about 1600. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on August 24, the pilot noted that the purpose of the flight was to show his passengers some Alaskan scenery. He said that as he approached his destination airport in level cruise flight at 1,200 feet agl, the engine began to run rough and lose power. He noticed that the carburetor air temperature was just above the carburetor ice zone marked in red on the gauge, so he applied full carburetor heat, which was followed by a complete loss of engine power. After completing the emergency procedures for a loss of engine power, the pilot said he was unable to restart the engine, and he selected a marshy tree-covered site as a forced landing area. During the forced landing, the airplane collided with trees, and sustained substantial damage to the fuselage and wings. The airplane was equipped with a naturally aspirated Teledyne Continental Motors O-470-K engine. The closest official weather observation station is at the Birchwood Airport. At 1753, an Aviation Routine Weather Report (METAR) was reporting, in part: Wind, 300 degrees (true) at 4 knots; visibility, 10 statute miles; clouds and sky condition, clear; temperature, 57 degrees F; dew point, 45 degrees F; altimeter, 29.58 inHg. The Birchwood Airport is situated adjacent to the ocean waters of the Cook Inlet. The temperature and dew point were entered into a carburetor icing probability chart, which coincided with the "serious icing-cruise power" category. On September 15, 2009, a Federal Aviation Administration (FAA) airworthiness inspector from the Anchorage Flight Standards District Office traveled to the Big Lake Airport, Big Lake, Alaska, and examined the airplane after it was recovered. The inspector reported that he was unable to find any preaccident mechanical problems with the airplane. ADDITIONAL INFORMATION The FAA's Advisory Circular (AC) 61-23C, Pilot's Handbook of Aeronautical Knowledge, Chapter 2, Carburetor Icing, states, in part: "... if the temperature is between -7 degrees C (20 degrees F) and 21 degrees C (70 degrees F), with visible moisture or high humidity, the pilot should be constantly on the alert for carburetor ice. During low or closed throttle setting, an engine is particularly susceptible to carburetor icing.” The FAA's AC 20-113, Pilot Precautions andProcedures to be taken in Preventing Aircraft Reciprocating Engine Induction System and Fuel System Icing Problems, states, in part: "Vaporization icing may occur at temperatures from 32 degrees F to as high as 100 degrees F with a relative humidity of 50 percent or above... . Since aviation weather reports normally include air temperature and dew point temperature, it is possible to relate the temperature/dew point spread to relative humidity. As the spread becomes less, relative humidity increases and becomes 100 percent when temperature and dew point are the same. In general, when the temperature/dew point spread reaches 20 degrees or less, you have a relative humidity of 50 percent or higher and are in potential icing conditions." ## Aircraft - Registration: [N4601A](https://openairdocs.org/deregistered/N4601A-2011-03-02), registration cancelled 2011-03-02, S/N 32199, built 1956 (OpenAirDocs) - Reported make and model: CESSNA 180 - Registry model: [Cessna 180](https://openairdocs.org/model/cessna-180) (registry code 2072602) (OpenAirDocs) - Registry engine: [Continental O-470 series](https://openairdocs.org/engine/continental-o-470-series) (registry code 17026, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 32199 - Airframe hours: 5824 - Engines: CONT MOTOR O-470 SERIES 230 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: Beam Douglas Jade - Registered owner: Beam Douglas Jade - Airworthiness certificate: Standard, Normal - Last inspection: Annual, February 26, 2009, 27 hours before - Departed: BCV, Chugiak, AK - Destination: BCV, Chugiak, AK ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 39; injuries: minor; airline transport; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review June 17, 2009; seat: left; flight hours: 6,266 total, 655 in this make and model, 4,855 as pilot in command, 112 in the last 90 days, 50 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: 8,000 ft broken - Temperature: 63 °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 20090824048579A](https://openairdocs.org/incident/20090824048579A), Aug 24, 2009: Cessna 180, Eklutna, AK, Substantial damage. During the return from a 1.5 hour local sightseeing flight, while @ 1200 AGL, the engine power hesitated. Pilot climbed to 1600 AGL and after leveling out, the… ## Other investigations on N4601A (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 ANC69D0104](https://openairdocs.org/ntsb/ANC69D0104), Jan 16, 1969: Cessna 180 (N4601A), Dillingham, AK, substantial damage - [NTSB ANC68F0024](https://openairdocs.org/ntsb/ANC68F0024), May 2, 1967: Cessna 180 (N4601A), Dillingham, AK, substantial damage ## Docket (1 files) The files NTSB released with the investigation on April 2, 2010, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=74585. 744 KB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 744 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40327949&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-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.