# NTSB CEN25LA322: Piper PA-18-150, N476SM, Joliet, IL, August 14, 2025

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Class 3 · Limited · Final report
- Date: August 14, 2025, 17:14 local (22:14 UTC)
- Place: Joliet, IL
- Coordinates: 41.515013, -88.152084 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=41.5150&lon=-88.1521&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Defining event: [Maneuvering: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report August 19, 2026
- Report: Approved by Office Director
- Investigation class: Class 3
- NTSB office: Central Region
- Parties: FAA
- NTSB case key (mKey): 200810
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN25LA322
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/200810/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=200810
- Page: https://openairdocs.org/ntsb/CEN25LA322

## Probable cause

The failure of the No. 2 cylinder exhaust valve, which resulted in a total loss of engine power.

## 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 · Failure (probable cause); cases with it: [Piper PA-18-150, 1 case](https://openairdocs.org/ntsb-findings/01058530/cases.md?model=7101828), [All aircraft, 373 cases](https://openairdocs.org/ntsb-findings/01058530/cases.md)

## Sequence of events

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

- [Maneuvering: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event); cases with it: [Piper PA-18-150, 18 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=7101828), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md)
- [Landing-landing roll: Collision during takeoff/land](https://openairdocs.org/ntsb-events/490); cases with it: [Piper PA-18-150, 25 cases](https://openairdocs.org/ntsb-events/490/sequence.md?model=7101828), [All aircraft, 1,309 cases](https://openairdocs.org/ntsb-events/490/sequence.md)

## Analysis

The pilot reported that he fueled the airplane and departed for a planned 3-hour banner tow flight. About two hours into the flight, he heard a “loud bang” from the engine, which resulted in strong vibrations and a gradual loss of engine power. Shortly after, the engine lost total power, and the pilot executed a forced landing to a field. During the landing roll, the airplane ground looped and impacted a fence, which resulted in substantial damage to the left elevator. Postaccident examination of the engine revealed that the No. 2 cylinder exhaust valve failed. Most of the valve stem remained inside the valve guide while the valve head was destroyed inside the cylinder. There were no other engine mechanical malfunctions or anomalies that would have precluded normal operation.

## Factual narrative

On August 14, 2025, at 1714 central daylight time, a Piper PA-18-150 airplane, N476SM, was substantially damaged when it was involved in an accident near Joliet, Illinois. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 banner tow flight. The pilot reported that he fueled the airplane and departed for a planned 3-hour banner tow flight in and around the Joliet area. About two hours into the flight, he heard a “loud bang” from the engine, which resulted in strong vibrations and a gradual loss of engine power. Shortly after, the engine lost total power, and the pilot executed a forced landing to a field. During the landing roll, the airplane ground looped and impacted a fence, which resulted in substantial damage to the left elevator. The responding FAA inspector reported that there was engine oil on the bottom of the fuselage from the engine cowling to the empennage. There was also oil leaking from the engine exhaust pipe area. Postaccident examination of the engine revealed that the No. 2 cylinder exhaust valve failed. Most of the valve stem remained inside the valve guide, while the valve head was destroyed inside the cylinder. There were no other engine mechanical malfunctions or anomalies that would have precluded normal operation. About 9 months and 440 hours before the accident, the No. 2 cylinder was replaced with a reworked cylinder. The engine had been inspected eight times since the cylinder was replaced with no discrepancies noted with the cylinder. The last seven inspections were in conjunction with an oil change, which were completed about every 50 to 75 hours.

## Aircraft

- Registration: [N476SM](https://openairdocs.org/aircraft/N476SM), registered now, S/N 18-7509080, built 1975 (OpenAirDocs)
- Reported make and model: PIPER PA-18-150
- Registry model: [Piper PA-18-150](https://openairdocs.org/model/piper-pa-18-150) (registry code 7101828) (OpenAirDocs)
- Registry engine: [Lycoming 0-320 series](https://openairdocs.org/engine/lycoming-0-320-series) (registry code 41508, reciprocating) (OpenAirDocs)
- Category: Airplane
- Serial number: 18-7509080
- Year built: 1975
- Airframe hours: 12252
- Engines: Lycoming O-360-C4P 180 horsepower reciprocating
- Damage: Substantial damage
- Flight: Banner tow, Part 91
- Operator: Drake Aerial Enterprises LLC, doing business as Air America Aerial Ads
- Registered owner: Tail Slide Aviation LLC
- Airworthiness certificate: Standard, Normal
- Last inspection: Annual, January 3, 2025, 440 hours before
- Departed: KJOT, Joliet, IL
- Equipment: ADS-B, Handheld GPS

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 21; injuries: none; commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, with waivers/limitations; last flight review August 26, 2024; seat: front; restraint: 4-point; flight hours: 1,088.9 total, 384.2 in this make and model, 986.3 as pilot in command, 352.6 in the last 90 days, 98.6 in the last 30 days, 5.6 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: calm
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 84 °F, dew point 61 °F
- Altimeter: 30.02 inHg
- Observed at: KJOT, 1 nm away
- METAR: KJOT 142215Z AUTO 00000KT 10SM CLR 29/16 A3002 RMK AO2 T02890159

## 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 20250814021609A](https://openairdocs.org/incident/20250814021609A), Aug 14, 2025: Piper PA-18-150, Joliet, IL, Substantial damage. On August 14, 2025, at approximately 1710 central daylight time, a Piper PA-18-150, [privacy data omitted], was substantially damaged when it was involved in…

## Docket (5 files)

The files NTSB released with the investigation on August 19, 2026, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=200810. 23.2 MB in all.

- Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 10 pages, 2.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19222361&FileExtension=pdf&FileName=6120%20-%20Pilot-Operator_Redacted-Rel.pdf
- FAA engine examination summary (item 2, PDF, 3 pages, 144 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19247665&FileExtension=pdf&FileName=Engine%20Teardown%20N476SM%20(FAA%20report)_Redacted-Rel.pdf
- Engine examination summary (item 3, PDF, 2 pages, 316 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19222087&FileExtension=pdf&FileName=Mechanic%20exam%20summary_Redacted-Rel.pdf
- Photos (item 4, PDF, 11 pages, 10 photos, 3.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19248224&FileExtension=pdf&FileName=Photos-Rel.pdf
- Maintenance records (engine) (item 5, PDF, 15 pages, 16.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19249562&FileExtension=pdf&FileName=Engine%20maintenance%20logs_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.