CHI93FA139 · Cessna 172I
Cessna 172I · Accident: fire/explosion en route
From 20Y · Monticello, MN to Waukegan National Airport (UGN)
Event
- NTSB case
- CHI93FA139
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Accident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- API-reported fatalities
- 2 · all aircraft and ground
- Ground fatalities
- 0
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- General aviation
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
Cessna 172I
- Aircraft type
- Cessna 172
- Category
- Airplane
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N8337L
- Operator
- Leo G. Stokes · private individual
- Onboard fatalities
- Unknown
- Route
- From 20Y · Monticello, MNTo Waukegan National Airport (UGN), Waukegan, IL
- Aircraft age
- Not recorded
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Part 91: General Aviation
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- En route · cruise
- First occurrenceThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- Fire/explosion
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Destroyed
Cause areas
- Hazardous material › Exploded
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
WITNESSES REPORTED THAT THE AIRPLANE FIRST SOUNDED NORMAL, AND THEN ITS ENGINE RPM INCREASED, FOLLOWED BY AN EXPLOSION & SMOKE. THREE WITNESSES OBSERVED THE AIRPLANE DURING AN UNCONTROLLED VERTICAL DESCENT. ONE STATED THE AIRPLANE EXPLODED APPROX 100 FT ABOVE THE GROUND. ANOTHER STATED HE OBSERVED THE AIRPLANE DESCENDING VERTICALLY, LOSING SIGHT OF IT JUST PRIOR TO OBSERVING FIRE AND SMOKE. THE THIRD STATED HE OBSERVED THE AIRPLANE FLYING STRAIGHT AND LEVEL, THEN SUDDENLY PITCH DOWN. DURING THE DESCENT, HE OBSERVED GREY SMOKE COMING FROM THE AIRPLANE. A CAN OF TCP FUEL TREATMENT WAS FOUND IN THE BURNT WRECKAGE. THE FILLER NECK AND CAP HAD DISTORTIONS WHICH DID NOT MATCH. TCP IS COMPRISED MAINLY OF TOLUENE, A HIGHLY VOLATILE SUBSTANCE. FUMES FROM A TOLUENE-BASED FLUID SUCH AS TCP COULD EXPLODE DURING THE LIGHTING OF A CIGARETTE. THE CAN WAS KEPT IN THE BAGGAGE COMPARTMENT BY THE OWNER. EIGHT PIECES OF WINDSHIELD PLEXIGLASS WERE FOUND AROUND THE IMPACT CRATER; THE REMAINDER OF THE WINDSHIELD WAS NOT FOUND.
Probable cause
AN INFLIGHT EXPLOSION OF A TOLUENE-BASED FLUID INSIDE THE AIRPLANE'S COCKPIT.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record CHI93FA139
- Event ID
- 20001211X12083
- Case number
- CHI93FA139
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
Source notes (4)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: 55c6ccb8db96b7cde02bf34eb959e08512ddb6b3d5139baf103b19a0992a0620; retrieved 2026-09-21T00:36:48.815Z.