# NTSB CEN24LA036: Textron 172S, N1817E, Erie, CO, November 9, 2023

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Class 3 · Limited · Final report
- Date: November 9, 2023, 09:30 local (16:30 UTC)
- Place: Erie, CO · 7CO0
- Coordinates: 40.070667, -105.0264 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=40.0707&lon=-105.0264&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Defining event: [Maneuvering: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340)
- Highest injury: No injuries
- Injuries: 2 uninjured
- Status: Completed, report October 22, 2025
- Report: Approved by Office Director
- Investigation class: Class 3
- NTSB office: Central Region
- Parties: FAA FSDO, Lycoming Engines
- NTSB case key (mKey): 193374
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN24LA036
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/193374/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=193374
- Page: https://openairdocs.org/ntsb/CEN24LA036

## Probable cause

A partial loss of engine power while maneuvering at a low altitude due to a stuck exhaust valve.

## Findings

NTSB's coded findings; those marked are part of the probable cause.

- [Engine (reciprocating): recip eng cyl section](https://openairdocs.org/ntsb-findings/01058530): Aircraft › Aircraft power plant · Malfunction (probable cause); cases with it: [Textron 172S, 1 case](https://openairdocs.org/ntsb-findings/01058530/cases.md?model=2072449), [All aircraft, 373 cases](https://openairdocs.org/ntsb-findings/01058530/cases.md)
- [Maintenance: scheduled/routine maintenance](https://openairdocs.org/ntsb-findings/02062010): Personnel issues › Task performance · Maintenance personnel; cases with it: [Textron 172S, 1 case](https://openairdocs.org/ntsb-findings/02062010/cases.md?model=2072449), [All aircraft, 320 cases](https://openairdocs.org/ntsb-findings/02062010/cases.md)

## Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event best describes what happened.

- [Maneuvering: 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)
- [Maneuvering: 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)
- [Emergency descent: 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-landing roll: 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

The flight instructor started the engine for the instructional flight, and it began to shake. The flight instructor shut down the engine, inspected it, and the alternator belt. Everything appeared to be normal, so he decided to restart the engine. After engine start, all indications were “in the green” and the engine no longer shook. All systems during the run-up appeared normal, and the instructor and student pilot departed. After completing several maneuvers, the flight instructor gave the student pilot a simulated emergency. The student pilot addressed the simulation with the appropriate steps and the airplane descended to about 700 ft above ground level (agl). As the student pilot applied full power to recover from the simulated emergency, the engine started to shake again. The flight instructor took the flight controls and observed that the engine rpm started to drop. The flight instructor maneuvered the airplane to land in a field. During the landing, the airplane rolled nose-first into a culvert and sustained substantial damage to the right wing and engine firewall. During the engine examination, no compression was observed at the No. 4 cylinder. Further examination revealed that the No. 4 exhaust valve was stuck open, and the No. 4 push rod was bent. No other anomalies were noted with the engine or systems that would have resulted in a loss of engine power. A review of the maintenance records revealed that a service bulletin (SB) to examine the exhaust valve and guide condition was not completed, nor was it required to be. The SB suggested that an inspection should be performed at every 1,000 hours of operation for engines equipped with Hi-Chrome exhaust valve guides, as the accident engine was. The partial loss of engine power was likely due to the stuck exhaust valve. Compliance with the engine manufacturer’s SB, although not required, may have prevented the stuck valve.

## Factual narrative

On November 9, 2023, about 0930 mountain daylight time, a Textron Aviation Inc. 172S, N1817E, was substantially damaged when it was involved in an accident near Erie, Colorado. The flight instructor and the student pilot were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. After a thorough pre-flight inspection, the flight instructor started the engine and the engine began to shake; also, the alternator was not charging the battery. The flight instructor shut the engine down and inspected both the engine and alternator belt. Everything appeared to be normal, so he decided to restart the engine. After the second engine start, all indications were “in the green” and the engine no longer shook. All systems during the run-up appeared normal. The flight instructor and student pilot departed and, after completing several maneuvers, the instructor gave the student a simulated engine fire. After completing the appropriate checklists, they entered a simulated emergency descent starting about 7,000 ft msl. The flight instructor reported that they transitioned into a simulated emergency landing and the student pilot chose a field, taking the simulated emergency descent down to about 700 ft agl. As the student pilot applied full power to recover from the simulated emergency, the engine started to shake again. The flight instructor took the flight controls and observed that the engine rpm started to drop. Since the engine was still running, and they were near an airport, the flight instructor maneuvered the airplane toward the airport. He set up to land on the runway, but the airplane was too high and fast. Engine rpm reduced to about 1,900, and the flight instructor decided to land the airplane in a field to avoid houses near the airport. The flight instructor maneuvered the airplane to land in a field, and the touchdown was uneventful. However, the field where the airplane landed sloped downward and during the landing roll the airplane rolled nose-first into a culvert. During the impact with the culvert, the airplane sustained substantial damage to the right wing and engine firewall. During the engine examination, compression was observed at cylinder Nos. 1, 2, and 3. However, no compression was observed in the No. 4 cylinder. Further examination revealed that the No. 4 exhaust valve was stuck open and the No. 4 push rod was bent. A borescope examination revealed no additional anomalies. Both magnetos produced sparks at all leads when the engine was rotated by hand at the propeller flange. The spark plugs appeared normal as compared to the Champion Aviation Check-a-Plug Chart AV-27. All the fuel injectors were found clear. A review of the maintenance records revealed that Lycoming Mandatory Service Bulletin 388C, Procedure to Determine Exhaust Valve and Guide Condition, had not been complied with, as suggested by the engine manufacturer. The SB stated that an inspection should be performed atevery 1,000 hours of operation if Hi-Chrome exhaust valve guides are installed. The inspection is intended to identify excessive carbon build up between the valve stem and the valve guide to prevent sticking valves or valve failure. The Hi-Chrome exhaust valve guides were installed on the accident airplane, as identified by the letter "C" stamped inside a circle on the engine cylinders.

## Aircraft

- Registration: [N1817E](https://openairdocs.org/aircraft/N1817E), registered now, S/N 172S12169, built 2018 (OpenAirDocs)
- Reported make and model: TEXTRON AVIATION INC 172S
- 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: 172S12169
- Year built: 2018
- Airframe hours: 4111
- Engines: Lycoming IO-360-L2A 180 horsepower reciprocating
- Damage: Substantial damage
- Flight: Instructional, Part 91
- Operator: Atp Aircraft 6 LLC
- Registered owner: Atp Aircraft 6 LLC
- Airworthiness certificate: Standard, Normal
- Last inspection: 100 hour, October 21, 2023
- Departed: BKBJ, Broomfiled, CO
- Equipment: Stall warning system, ADS-B, Electronic flight bag or handheld device, Electronic multifunction display

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Flight instructor; age 26; injuries: none; flight instructor, commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, waiver time limited special; last flight review July 11, 2023; seat: right; restraint: 3-point; flight hours: 493 total, 389 in this make and model, 416 as pilot in command, 204 in the last 90 days, 34 in the last 30 days, 1 in the last 24 hours
- Student pilot; age 32; injuries: none; student; medical: class 1, without waivers/limitations; seat: left; restraint: 3-point; flight hours: 88 total, 88 in this make and model, 10 as pilot in command, 75 in the last 90 days, 18 in the last 30 days, 1 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 20° at 3 knots
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 37 °F, dew point 28 °F
- Altimeter: 30.28 inHg
- Observed at: KEIK, 3 nm away
- METAR: KEIK 091615Z AUTO 02003KT 10SM CLR 03/M02 A3028 RMK AO2 T00321016

## 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 20231109019089A](https://openairdocs.org/incident/20231109019089A), Nov 9, 2023: Textron Aviation Inc 172S, Erie, CO, Substantial damage. On November 9, 2023 at about 1217PM local time, a Cessna 172S landed off-field, resulting in substatial damage to the aircraft. No injuries resulted from the…

## Docket (6 files)

The files NTSB released with the investigation on October 22, 2025, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=193374. 5.6 MB in all.

- Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 9 pages, 1.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18616832&FileExtension=pdf&FileName=NTSB%20Form%206120%20Pilot%20Operator%20Report%20CEN24LA036_Redacted-Rel.pdf
- Flight instructor statement to FAA (item 2, PDF, 1 page, 862 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19181353&FileExtension=pdf&FileName=Flight%20Instructor%20Statement%20to%20FAA_Redacted-Rel.pdf
- Engine examination (item 3, PDF, 1 page, 85 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19178604&FileExtension=pdf&FileName=Engine%20Examination%20Notes-Rel.pdf
- Photo array (item 4, PDF, 6 pages, 1.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19179898&FileExtension=pdf&FileName=Accident%20Report%20Photographs%20-%20CEN24LA036-Rel.pdf
- Lycoming mandatory service bulletin 388C (item 5, PDF, 13 pages, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18918648&FileExtension=pdf&FileName=Lycoming%20SB%20388C-Rel.pdf
- Lycoming service instruction - exhaust valve and guide identification procedures (item 6, PDF, 2 pages, 149 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18919802&FileExtension=pdf&FileName=Lycoming%20Service%20Instruction%201485A%201000hr%20Valve%20Inspection-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.

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