# NTSB CEN24LA350: Cessna 172, N20747, Englewood, CO, September 11, 2024 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Class 3 · Limited · Final report - Date: September 11, 2024, 09:40 local (15:40 UTC) - Place: Englewood, CO - Coordinates: 39.544742, -104.84893 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=39.5447&lon=-104.8489&mi=10 - Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping) - Defining event: [Initial climb: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) - Highest injury: Minor injuries - Injuries: 1 minor, 1 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Central Region - Parties: All ATP, FAA FSDO, Lycoming Engines - NTSB case key (mKey): 195102 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN24LA350 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/195102/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=195102 - Page: https://openairdocs.org/ntsb/CEN24LA350 ## Probable cause A partial loss of engine power due to fuel-oil contamination of the fuel injection servo. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine fuel and control: fuel control/carburetor](https://openairdocs.org/ntsb-findings/01057322): Aircraft › Aircraft power plant · Damaged/degraded (probable cause); cases with it: [Textron 172S, 1 case](https://openairdocs.org/ntsb-findings/01057322/cases.md?model=2072449), [All aircraft, 195 cases](https://openairdocs.org/ntsb-findings/01057322/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Initial climb: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) (defining event); cases with it: [Textron 172S, 2 cases](https://openairdocs.org/ntsb-events/340/sequence.md?model=2072449), [All aircraft, 820 cases](https://openairdocs.org/ntsb-events/340/sequence.md) - [Initial climb: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342); cases with it: [Textron 172S, 3 cases](https://openairdocs.org/ntsb-events/342/sequence.md?model=2072449), [All aircraft, 1,858 cases](https://openairdocs.org/ntsb-events/342/sequence.md) - [Initial climb: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Textron 172S, 3 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=2072449), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) - [Landing: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Textron 172S, 6 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=2072449), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis While performing touch-and-go landings, the flight instructor and student pilot noticed a partial loss of engine power on climbout, about 200 ft above ground level (agl). The flight instructor reported the tachometer read 2,100 and then 1,600 rpm. During a forced landing to a golf course, the airplane’s nose landing gear collapsed and the airplane came to rest inverted. A postimpact test of the engine’s fuel injection servo found fuel flow below the minimum service limit at most test points. When the servo was disassembled, a thick blue liquid consistent with a fuel-oil mixture was found in the venturi chambers. Oil residue was noted in the hex plug and air diaphragm, the spring and stem assembly, and the air passage to the air diaphragm. No other anomalies were detected with the engine. A service bulletin from the fuel injection servo manufacturer states that this type of contamination could cause an engine to exhibit “gradually deteriorating idle, difficulty starting and/or cold engine acceleration performance.” The flight school was aware of the service bulletin and was inspecting airplanes that had the engine symptoms listed in the service bulletin. It is likely that contamination of the fuel injection servo resulted in a partial loss of engine power and subsequent forced landing. ## Factual narrative On September 11, 2024, about 0940 mountain daylight time, a Cessna 172S airplane, N20747, was substantially damaged when it was involved in an accident near Englewood, Colorado. The flight instructor was not injured and the student pilot sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. The pilots were performing touch-and-go landings on runway 17R at Centennial Airport (APA), Englewood, Colorado. On climbout for the traffic pattern, when the airplane was about 200 ft agl, the pilots noticed a partial loss of engine power. The instructor reported the tachometer read 2,100 and then 1,600 rpm. He performed a forced landing to a golf course. During the landing roll, the airplane’s nose landing gear collapsed and the airplane came to rest inverted. A review of maintenance logbook entries found that on September 5, 2024, about one week before the accident flight, another pilot reported that the airplane “was only getting 2,000 rpm at max power and was backfiring constantly in the run-up.” However, maintenance personnel found that the engine operated satisfactorily during a subsequent ground run-up. The airplane was then flown daily without any reported engine problems until the accident takeoff. A postimpact examination of the engine revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation. However, during a bench test of the engine’s fuel injection servo (AVStar part number LFR-NNSS5), fuel flow was below the minimum service limit at most test points. When the servo was disassembled, a thick blue liquid consistent with a fuel-oil mixture was found in the venturi chambers. Oil residue was noted in the hex plug and air diaphragm, the spring and stem assembly, and the air passage to the air diaphragm. The AVStar LFR-NNSS5 is a variant of the RSA-5AD1 fuel injection servo and was mounted in an updraft configuration on the accident airplane. AVStar service bulletin AFS-SB10, Fuel Servos Installed in an Updraft Configuration, is applicable to RSA-5AD1 servos and states: There have been occasional reports of servo equipped engines that exhibit one or more of the following characteristics - gradually deteriorating idle, difficulty starting and/or cold engine acceleration performance. These engines may have the servo mounted in an updraft, or nearly updraft configuration. Close inspection of the servo may reveal oily contaminant in the bore of the servo that is green/blue in color. It is also possible for this contaminant to migrate into the air section of the regulator. The Precision Airmotive service information letter SIL RS-40, Service Information For RSA-5 Series Fuel Injection Servos Installed in Updraft Configuration, similarly notes reports of reduced engine performance and recommends inspection of fuel injection servos for contamination if these problems are experienced. The flight school’s maintenance personnelstated they were aware of AVStar AFS-SB10 and Precision Airmotive SIL ARS-40 and routinely inspected their airplanes that had any symptoms listed in AFS-SB10. In addition, they reported that they caution their pilots against over-priming the engine during engine starts. ## Aircraft - Registration: [N20747](https://openairdocs.org/aircraft/N20747), registered now, S/N 172S12578, built 2020 (OpenAirDocs) - Reported make and model: CESSNA 172 (S) - Registry model: [Textron 172S](https://openairdocs.org/model/textron-172s) (registry code 2072449) (OpenAirDocs) - Registry engine: [Lycoming IO-360-L2A](https://openairdocs.org/engine/lycoming-io-360-l2a) (registry code 41597, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 172S12578 - Year built: 2020 - Airframe hours: 3448 - Engines: LYCOMING IO-360-L2A 180 horsepower reciprocating - Damage: Substantial damage - Flight: Instructional, Part 91 - Operator: ATP Flight School - Registered owner: Atpce LLC - Airworthiness certificate: Standard, Normal; Standard, Utility - Last inspection: 100 hour, August 28, 2024, 65 hours before - Equipment: Electronic multifunction display, Electronic flight bag or handheld device, ADS-B, Stall warning system, Onboard weather, Electronic primary flight display ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 25; injuries: none; flight instructor, commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, with waivers/limitations; last flight review March 6, 2024; seat: right; restraint: 3-point; flight hours: 720 total, 607 in this make and model, 675 as pilot in command, 283 in the last 90 days, 64 in the last 30 days, 5 in the last 24 hours - Student pilot; age 33; injuries: minor; seat: left; restraint: 3-point; flight hours: 18 total, 18 in this make and model, 18 in the last 90 days, 18 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 300° at 7 knots - Visibility: 10 statute miles - Lowest ceiling: 22,000 ft broken - Temperature: 72 °F, dew point 39 °F - Altimeter: 30.02 inHg - Observed at: KAPA, 1 nm away - METAR: KAPA 111553Z 30007KT 10SM FEW130 BKN220 22/04 A3002 RMK AO2 SLP095 T02220039 ## 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 20240911012829A](https://openairdocs.org/incident/20240911012829A), Sep 11, 2024: Textron Aviation Inc 172S, Centennial, CO, Substantial damage. On 09/11/2024 at approximately (09:40 am) hrs. (MDT), Cessna C-172, Centennial Airport, CO., (kapa) during pattern practicing takeoff and landing, pilot noted… ## Docket (8 files) The files NTSB released with the investigation on May 8, 2025, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=195102. 8.5 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 10 pages, 5.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18450815&FileExtension=pdf&FileName=NTSB%206120%20cen24la350_Redacted-Rel.pdf - Photos (item 2, PDF, 3 pages, 2 photos, 648 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18451073&FileExtension=pdf&FileName=cen24la350%20photos%202-Rel.pdf - Engine examination summary (item 3, PDF, 7 pages, 829 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18474152&FileExtension=pdf&FileName=Exmination%20Summary%20CEN24LA350-1-Rel.pdf - Fuel servo examination summary (item 4, PDF, 2 pages, 2 photos, 299 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18450825&FileExtension=pdf&FileName=MOR%20Fuel%20Servo%20Examination-Rel.pdf - Maintenance log entries (item 5, PDF, 2 pages, 479 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18451229&FileExtension=pdf&FileName=Pages%20from%20N20747%20Engine%20Log_Redacted-Rel.pdf - Service information (item 6, PDF, 6 pages, 483 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18451363&FileExtension=pdf&FileName=Service%20Information-Rel.pdf - Record of conversation strohl (item 7, PDF, 1 page, 62 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18644072&FileExtension=pdf&FileName=MOR%20-%20Strohl-Rel.pdf - Party forms (item 8, PDF, 2 pages, 606 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18451966&FileExtension=pdf&FileName=cen24la350%20party%20forms_Redacted-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.