# NTSB CHI89IA179: Boeing 767-231, N608TW, Knox, IN, September 5, 1989

- Type: NTSB incident investigation
- Classification: Incident · Minor injuries · Incident investigation · Final report
- Date: September 5, 1989, 17:52 local (21:52 UTC)
- Place: Knox, IN
- Coordinates: 41.289653, -86.620162 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=41.2897&lon=-86.6202&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 6 minor, 156 uninjured
- Status: Completed, report October 8, 1992
- Report: Approved by Office Director
- NTSB case key (mKey): 14289
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI89IA179
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/14289/pdf
- Page: https://openairdocs.org/ntsb/CHI89IA179

## Probable cause

THE RADAR CONTROLLLER'S FAILURE TO MAINTAIN RADAR SEPARATION. FACTORS CONTRIBUTING TO THE INCIDENT WERE: MISUNDERSTANDING OF AN ATC INSTRUCTION BY THE PILOT OF THE INCIDENT AIRPLANE, AND UNCLEAR PHRASEOLOGY USED IN THE INSTRUCTIONS ISSUED BY THE RADAR CONTROLLER.

## Sequence of events

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

- Near collision between aircraft, cruise - normal
  - interpretation of instructions - not understood, pilot in command (contributing factor)
  - information unclear(phraseology), atc personnel(artcc) (contributing factor)
  - radar separation - not maintained, atc personnel(artcc) (cause)

## Analysis

THIS AIRPLANE WAS INVOLVED IN A NEAR COLLISION WITH ANOTHER AIRPLANE WHILE IN POSITIVE CONTROL AIRSPACE. BOTH AIRPLANES TOOK EVASIVE ACTION. VISIBILITY WAS REPORTED BY BOTH FLIGHT CREWS AS BEING REDUCED BY THE PRESENCE OF CIRRUS CLOUDS WITH NO VISIBLE HORIZON. THIS AIRPLANE HAD ACKNOWLEDGED AND RESPONDED TO A TURN INSTRUCTION ISSUED TO A THIRD AIRPLANE WITH A SIMILAR CALL SIGN, AND TURNED TO A HEADING WHICH PUT THE TWO INVOLVED AIRPLANES ON AN INTERSECTING COURSE. THE TURN INSTRUCTION WAS CHALLENGED BY THE AIRPLANE FOR WHOM IT WAS INTENDED, BUT THE INCIDENT AIRPLANE WAS NEVER TURNED BACK TO ITS ORIGINAL HEADING. THE ERROR WAS DISCOVERED A SHORT TIME LATER BY THE MANUAL CONTROLLER AND POINTED OUT TO THE RADAR CONTROLLER. HE ISSUED TURN AND CLIMB INSTRUCTIONS TO THE INCIDENT AIRPLANE ALONG WITH A TRAFFIC ADVISORY. CORRELATION OF THE TWO DFDR READOUTS WITH RADAR TRACK DATA SHOW, THAT AT THE POINT OF CLOSEST APPROACH, VERTICAL SEPARATION WAS BETWEEN 95 AND 200 FT.

## Aircraft

- Registration: N608TW (not matched to a registry record)
- Reported make and model: BOEING 767-231
- Category: Airplane
- Engines: P&W JT9D-7R4D turbo fan
- Damage: No damage
- Flight: Part 121
- Operator: Trans World Airlines Inc.
- Departed: STL, ST LOUIS, MO
- Destination: PARIS, FRANCE, OF
- Flight plan: IFR
- Airport: NONE

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; airline transport; airplane ratings: multi-engine land; instrument ratings: airplane; medical: class 1, unknown

## Weather

- Conditions: Instrument (IMC), Day
- Temperature: -0 °F, dew point -0 °F

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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