American Eagle Flight 4146
Aerospatiale ATR-42-300 · Accident: vortex turbulence encountered on approach
From Central Wisconsin Airport (CWA) to Chicago O'Hare International Airport (ORD)
Event
- NTSB case
- CHI98LA351
- 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
- Airline
- 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
Aerospatiale ATR-42-300
- Aircraft type
- Aerospatiale ATR-42
- 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
- N233RM
- Operator
- American Eagle
- Onboard fatalities
- Unknown
- Route
- From Central Wisconsin Airport (CWA), Mosinee, WITo Chicago O'Hare International Airport (ORD)
- 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 121: Air Carrier
- 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
- Approach
- 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
- Vortex turbulence encountered
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- None
Cause areas
- Wake turbulence › Encountered
Approximate · Estimated position: the centre of Chicago, IL, the place the record names. Not the accident site.
NTSB narrative
Flight 146, an ATR-42 was approximately 18 miles from the airport on the ILS 09R approach when it encountered wake turbulence from a Flight 554, a Boeing 737-300, which was vectored onto the approach from the north in front of Flight 146. Radar data showed Flight 554 intercepted the localizer approximately 17.5 miles from the airport while descending from 5,200 feet to 4,800 feet. Flight 146 was at an altitude of about 4,900 feet when the wake turbulence encounter occurred. Separation of the two airplanes when the encounter occurred was approximately 4.8 miles. Vertical acceleration of Flight 146 varied from 2.3679 g's to .5542 g's during the encounter.
Probable cause
the wake turbulence encountered by Flight 146.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record CHI98LA351
- Event ID
- 20001211X11023
- Case number
- CHI98LA351
- 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: local date, investigation status, damage. Values present in the bulk record are kept.
- The date is the local date; the NTSB stores the UTC date 1998-09-18.
- API snapshot SHA-256: f83029f3ca2a0349fe7afd02f8d76e11a798ba81a4fa38e1e182a690913b1bc4; retrieved 2026-09-18T17:04:47.519Z.