CHI90FA233 · Piper PA-23-160
Piper PA-23-160 · Accident: partial loss of engine power (mechanical failure) en route
From Central Illinois Regional Airport at Bloomington-Normal (BMI) to Chicago Midway International Airport (MDW)
Event
- NTSB case
- CHI90FA233
- 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
- 0 · 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
Piper PA-23-160
- Aircraft type
- Piper PA-23
- 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
- N4231P
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From Central Illinois Regional Airport at Bloomington-Normal (BMI), Bloomington, ILTo Chicago Midway International Airport (MDW), Chicago, 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
- Partial loss of engine power (mechanical failure)
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Substantial
Cause areas
- Fuel system, carburetor › Blocked(partial)
- Ignition system, ignition lead › Failure, partial
- Ignition system, magneto › Contamination
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
DURING FLIGHT THE LEFT ENGINE BEGAN RUNNING ROUGH AND VIBRATING SEVERELY, AND IT WAS SHUT DOWN. THE PILOT WAS UNABLE TO MAINTAIN ALTITUDE ON THE RIGHT ENGINE AND A FORCED LANDING WAS MADE IN AN ALFALFA FIELD. EXAMINATION REVEALED THAT THE LEFT ENGINES RIGHT MAGNETO HAD AN ACCUMULATION OF OIL INSIDE ITS CASE. IN ADDITION, THE SPARK PLUG LEAD FROM THE LEFT MAGNETO FOR THE #1 CYLINDER WAS INTERNALLY DAMAGED. EXAMINATION OF THE RIGHT ENGINE REVEALED THAT THE INTAKE DUCT BETWEEN THE AIR FILTER AND THE CARBURETOR WAS DETERIORATED FROM EXPOSURE TO HOT EXHAUST PIPES. A 3' X 1/2' PIECE OF THE DUCT HAD SEPARATED AND WAS FOUND CAUGHT ON THE CARBURETOR VENTURI.
Probable cause
A LOSS OF LEFT ENGINE POWER DUE TO OIL ACCUMULATION IN THE RIGHT MAGNETO AND A NON-USABLE SPARK LEAD FROM THE LEFT MAGNETO. IN ADDITION, THE RIGHT ENGINE WAS UNABLE TO PROVIDE ADEQUATE POWER TO MAINTAIN ALTITUDE DUE TO A PARTIAL BLOCKAGE IN THE CARBURETOR BY A SECTION OF AIR INTAKE DUCT WHICH CAUSED THE ENGINE TO RUN RICH.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record CHI90FA233
- Event ID
- 20001212X23931
- Case number
- CHI90FA233
- 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: 5ef13a5a4d06d5c57a28a9f7df2b40c0433af501ad4ffa47dd882962fd94ba66; retrieved 2026-09-23T05:25:09.100Z.