# NTSB MKC87IA034: Embraer Brasilia EMB-120, N223AS, Fort Smith, AR, December 23, 1986

- Type: NTSB incident investigation
- Classification: Incident · No injuries · Incident investigation · Final report
- Date: December 23, 1986, 06:20 local (12:20 UTC)
- Place: Fort Smith, AR
- Coordinates: 35.369861, -94.420082 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=35.3699&lon=-94.4201&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 6 uninjured
- Status: Completed, report March 30, 1988
- Report: Approved by Office Director
- NTSB case key (mKey): 34305
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=MKC87IA034
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/34305/pdf
- Page: https://openairdocs.org/ntsb/MKC87IA034

## Sequence of events

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

- Airframe/component/system failure/malfunction, cruise
  - reduction gear assy - fatigue (cause)
  - remedial action - initiated, pilot in command
- Loss of engine power(total) - mech failure/malf, descent
  - engine assembly - failure,total
  - emergency procedure - performed, pilot in command

## Analysis

THE FLIGHT CREW STATED THAT THEY WERE INITIATING A DESCENT INTO FINAL APPROACH FOR A LANDING WHEN THE RIGHT ENGINE GEARBOX CHIP DETECTOR LGITH ILLUMINATED FOLLOWED BY A LOUD BANG AND SEVERE VIBRATION.WHEN THE PROPELLER WAS FEATHERED AND THE ENGINE SHUT DOWN WITH THE CONDITION LEVER THE ROTATION AND VIBRATION STOPPED, THE CREW FURTHER STATED. THE AIRCRAFT LANDED WITHOUT FURTHER INCIDENT. A POST-INCIDENT TEARDOWN INSPECTION OF THE POWERPLANT AT THE FACTORY REVEALED A SUDDEN AND CATASTROPHIC FAILURE OF THE PROPELLER REDUCTION GEARBOX ASSEMBLY DUE TO A HIGH CYCLE, METAL FATIGUE FRACTURE ON ONE, OF TWO, HELICAL GEARS. TEARDOWN AND INSEPCTION OF THE PROPELLER ASSEMBLY REVEALED SEVERE DAMAGE TO THE COMPOSITE PLASTIC BLADE RETAINER RINGS AND METAL ACTUATOR YOKES DUE TO SUDDEN DECELERATION AND STOPPAGE.

## Aircraft

- Registration: N223AS (not matched to a registry record)
- Reported make and model: EMBRAER BRASILIA EMB-120 (BRASILIA E)
- Category: Airplane
- Serial number: 120.021
- Airframe hours: 329
- Engines: P&W PW118 1600 horsepower turbo prop
- Damage: Minor damage
- Flight: Part 135
- Registered owner: Atlantic Southeast Airlines
- Airworthiness certificate: Standard, Transport
- Departed: FYV, FAYETTEVILLE, AR
- Destination: FSM, FORT SMITH, AR
- Flight plan: IFR
- Airport: Fort Smith Municip

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 24; commercial, airline transport; airplane ratings: multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: left; flight hours: 3,460 total, 3,260 as pilot in command

## Weather

- Conditions: Visual (VMC), Dawn
- Wind: 30° at 6 knots
- Visibility: 7 statute miles
- Lowest ceiling: 5,500 ft overcast
- Temperature: 43 °F, dew point 37 °F
- Altimeter: 29.00 inHg
- Observed at: FSM, 5 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).

- [Accident 19861223087219A](https://openairdocs.org/incident/19861223087219A), Dec 23, 1986: Emb EMB120, Fort Smith, AR, Substantial damage. Lost power to right engine on final approach. Engine shut down. Found failure of propeller reduction gearbox.

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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