# NTSB CEN24LA362: Cessna 172N, N739JU, Arboles, CO, September 17, 2024 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Class 3 · Limited · Final report - Date: September 17, 2024, 10:55 local (16:55 UTC) - Place: Arboles, CO - Coordinates: 37.12, -107.39 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=37.1200&lon=-107.3900&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Fuel related](https://openairdocs.org/ntsb-events/190) - Highest injury: Serious injuries - Injuries: 1 serious, 1 minor - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Central Region - Parties: FAA - NTSB case key (mKey): 195158 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN24LA362 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/195158/pdf - Page: https://openairdocs.org/ntsb/CEN24LA362 ## Probable cause A loss of engine power due to carburetor ice. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Temp/humidity/pressure: conducive to carburetor icing](https://openairdocs.org/ntsb-findings/03031030): Environmental issues › Conditions/weather/phenomena · Effect on equipment (probable cause); cases with it: [Cessna 172N, 6 cases](https://openairdocs.org/ntsb-findings/03031030/cases.md?model=2072434), [All aircraft, 435 cases](https://openairdocs.org/ntsb-findings/03031030/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-cruise: Fuel related](https://openairdocs.org/ntsb-events/190) (defining event); cases with it: [Cessna 172N, 3 cases](https://openairdocs.org/ntsb-events/190/sequence.md?model=2072434), [All aircraft, 361 cases](https://openairdocs.org/ntsb-events/190/sequence.md) - [Emergency descent: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Cessna 172N, 31 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=2072434), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) ## Analysis The pilot reported that during the flight, at an altitude of 1,800 ft above the ground, she encountered an area of light rain, so she applied carburetor heat as a precaution. Once carburetor heat was applied, the engine began to run rough and lose power. The pilot turned the carburetor heat on and off a few times because she was not sure if the introduction of the carburetor heat was making the loss of power worse. The pilot also completed the checklist for engine roughness. Unable to clear up the engine roughness and unable to maintain airplane altitude, the pilot performed a forced landing. The fuselage and right wing sustained substantial damage when the airplane impacted trees and terrain. A postaccident examination of the engine and fuel system did not reveal any preexisting anomalies or failures that would have precluded normal operation. Ample fuel drained from the wing fuel tanks before the wreckage was recovered; however, the amount of fuel drained was not documented. The recorded temperature and dew point near the accident site were conducive to “serious icing” at cruise engine power settings. Based on this information, it is likely that carburetor ice formed and there was insufficient time/altitude for the carburetor heat to melt the accumulated ice. ## Factual narrative On September 17, 2024, about 1055 mountain daylight time, a Cessna 172N, N739JU, was substantially damaged when it was involved in an accident near Arobles, Colorado. The pilot sustained minor injuries, and the passenger was seriously injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot was taking a friend on a local flight when, about 1,800 ft above ground level, the airplane flew into an area of light rain. The pilot applied carburetor heat as a precaution. Despite having the carburetor heat engaged while the airplane flew in the rain, the engine began to run rough and lose power. The pilot turned the carburetor heat on and off a few times because they were not sure if the introduction of the carburetor heat was making the situation worse. The pilot also completed the checklist for engine roughness. Unable to clear up the engine roughness and unable to maintain airplane altitude, the pilot initiated an off airport forced landing, and the airplane fuselage and right wing sustained substantial damage when it impacted trees and terrain. The pilot estimated that the flight departed with a 26-gallon fuel load. The accident occurred about 35 minutes after departure, and according to airplane performance charts, the airplane’s expected fuel consumption rate was 5 to 8.5 gallons per hour. After the accident, ample fuel was drained from the wing tanks before the wreckage was recovered; however, the amount of fuel drained was not documented. The recorded temperature and dew point near the accident site were conducive to “serious icing” at cruise engine power settings. The pilot stated that the carburetor heat was working properly when checked before departure. According to FAA Advisory Circular 20-113, "To prevent accident due to induction system icing, the pilot should regularly use [carburetor] heat under conditions known to be conducive to atmospheric icing and be alert at all times for indications of icing in the fuel system." The circular recommended that when operating in conditions where the relative humidity is greater than 50 percent, "…apply carburetor heat briefly immediately before takeoff, particularly with float type carburetors, to remove any ice which may have been accumulated during taxi and runup." It also stated, "Remain alert for indications of induction system icing during takeoff and climb-out, especially when the relative humidity is above 50 percent, or when visible moisture is present in the atmosphere." ## Aircraft - Registration: [N739JU](https://openairdocs.org/aircraft/N739JU), registered now, S/N 17270587, built 1978 (OpenAirDocs) - Reported make and model: CESSNA 172N - Registry model: [Cessna 172N](https://openairdocs.org/model/cessna-172n) (registry code 2072434) (OpenAirDocs) - Registry engine: [Lycoming 0-320 series](https://openairdocs.org/engine/lycoming-0-320-series) (registry code 41508, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 17270587 - Year built: 1978 - Airframe hours: 6206 - Engines: Lycoming O-320 160 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: Gregg Flying Service Inc - Registered owner: Gregg Flying Service Inc - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, September 1, 2024 - Departed: 00C, Durango, CO - Airport: 00C, Animas Airpark - Equipment: Stall warning system, ADS-B ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 33; injuries: minor; airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review July 8, 2024; seat: right; restraint: 3-point; flight hours: 3,180 total, 220 in this make and model, 2,390 as pilot in command, 120 in the last 90 days, 16 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Visibility: 4 statute miles - Lowest ceiling: 2,600 ft broken - Temperature: 57 °F, dew point 54 °F - Altimeter: 30.10 inHg - Observed at: KDRO, 18 nm away - METAR: KDRO 171653Z AUTO VRB04KT 4SM TSRA BR SCT016 BKN026 OVC060 14/12 A3010 ## 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 20240917017209A](https://openairdocs.org/incident/20240917017209A), Sep 17, 2024: Cessna 172N, Pagosa Springs, CO, Substantial damage. Aircraft departed animas airpark (00C) near durango at 10:00 a.m. for lake navajo, CO for a discovery flight. After approximately 30 minutes after taking off,… 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.