# NTSB CHI92IA030: Aerospatiale ATR-42-300, N235RM, Chicago, IL, November 20, 1991

- Type: NTSB incident investigation
- Classification: Incident · Minor injuries · Incident investigation · Final report
- Date: November 20, 1991, 13:43 local (19:43 UTC)
- Place: Chicago, IL
- Location: 41.8500° N, 87.6501° W: Placed by OpenAirDocs: center of Chicago, IL, within about 9 miles (OpenAirDocs)
- Nearby events: https://openairdocs.org/map.md?lat=41.8500&lon=-87.6501&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 1 minor, 21 uninjured
- Status: Completed, report May 5, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 15319
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI92IA030
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/15319/pdf
- Page: https://openairdocs.org/ntsb/CHI92IA030

## Probable cause

AN INFLIGHT ENCOUNTER WITH WAKE TURBULENCE DURING CRUISE FLIGHT.

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Vortex turbulence encountered, cruise
  - wake turbulence - encountered (cause)

## Analysis

THE INCIDENT AIRPLANE ENCOUNTERED VORTEX TURBULENCE WHILE FOLLOWING RADAR VECTORS FOR LANDING SEQUENCE.  THE AIRPLANE WAS NOT DAMAGED.  A FLIGHT ATTENDANT SUSTAINED MINOR INJURIES DURING THE ENCOUNTER.  THE AIRPLANE WAS OPERATING IN A TERMINAL CONTROL AREA UNDER POSITIVE RADAR CONTROL.  FAA RECORDS AND RADAR TRACK DATA SHOW A LIKE CATEGORY AIRPLANE WAS APPROXIMATELY 4 NAUTICAL MILES IN FRONT OF THE INCIDENT AIRPLANE WHEN IT DESCENDED TO AND MAINTAINED THE SAME ALTITUDE AS THE INCIDENT AIRPLANE. THE INCIDENT AIRPLANE WAS PROCEEDING ALONG APPROXIMATELY THE SAME GROUND TRACK AS THE LEAD AIRPLANE AND ENCOUNTERED THE TURBULENCE NEAR THE POINT THE LEAD AIRPLANE LEVELED AT THE SAME ALTITUDE.  AT THE TIME OF THE ENCOUNTER THE LATERAL SEPARATION OF THE TWO AIRPLANES WAS 4.6 NAUTICAL MILES.  THE MINIMUM ATC SEPARATION IN A RADAR ENVIRONMENT WHEN THE AIRCRAFT ARE WITHIN 40 NAUTICAL MILES OF THE RADAR ANTENNA IS THREE NAUTICAL MILES.

## Aircraft

- Registration: N235RM (not matched to a registry record)
- Reported make and model: AEROSPATIALE ATR-42-300 (ATR42-300)
- Category: Airplane
- Serial number: 235
- Engines: P&W PW120 1800 horsepower turbo prop
- Damage: No damage
- Flight: Part 121
- Operator: Simmons Airlines Inc., doing business as American Eagle
- Registered owner: Gpa Atr II Inc.
- Airworthiness certificate: Standard, Transport
- Last inspection: Unknown, January 2, 2000
- Departed: SBN, SOUTH BEND, IN
- Flight plan: IFR

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 42; airline transport; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, unknown; seat: left; flight hours: 10,337 total, 2,018 in this make and model

## Weather

- Conditions: Visual (VMC), Day
- Wind: 360° at 8 knots
- Visibility: 15 statute miles
- Lowest ceiling: 11,000 ft broken
- Altimeter: 30.00 inHg
- Observed at: ORD, 15 nm away

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Incident 19911120062039I](https://openairdocs.org/incident/19911120062039I), Nov 20, 1991: Aerosp ATR42300, Chicago, IL. Encountered severe turbulence behind B727 flight on approach. Flight attendant received minor injury.

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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