# NTSB SEA95IA021: Fairchild SA227, N380PH, Missoula, MT, November 17, 1994

- Type: NTSB incident investigation
- Classification: Incident · No injuries · Incident investigation · Final report
- Date: November 17, 1994, 06:35 local (13:35 UTC)
- Place: Missoula, MT
- Coordinates: 46.849079, -113.990249 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=46.8491&lon=-113.9902&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 4 uninjured
- Status: Completed, report July 31, 1995
- Report: Approved by Office Director
- NTSB case key (mKey): 42070
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA95IA021
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/42070/pdf
- Page: https://openairdocs.org/ntsb/SEA95IA021

## Probable cause

THE FATIGUE FAILURE OF THE FIRST STAGE COMPRESSOR IMPELLER.

## Sequence of events

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

- Loss of engine power(total) - mech failure/malf, cruise
  - compressor assembly,impeller - fatigue (cause)
  - compressor assembly,impeller - failure

## Analysis

WHILE IN CRUISE FLIGHT, THE FIRST STAGE COMPRESSOR IMPELLER OF THE NUMBER TWO ENGINE EXPERIENCED A TOTAL FAILURE. THE CREW THEN ELECTED TO MAKE A PRECAUTIONARY LANDING AT AN ALTERNATE AIRPORT. A METALLURGICAL ANALYSIS REVEALED THAT THE IMPELLER HAD EXPERIENCED A LOW CYCLE FATIGUE FRACTURE.

## Factual narrative

On November 17, 1994, about 0635 mountain standard time (MST), a Fairchild SA227, N380PH, experienced a contained engine failure while en route from Helena, Montana to Spokane, Washington. The airline transport rated captain, his first officer, and the two passengers were not injured, and the aircraft sustained minor damage. The FAR Part 135 passenger flight, which departed Helena at 0608 MST, was operating in visual meteorological conditions at the time of the engine failure. The aircraft was on an IFR flight plan, and there was no ELT activation.

According to the operator, the number two engine failed while the aircraft was in cruise flight, and the crew diverted to Missoula, Montana. At Missoula, a successful precautionary landing was completed about 15 minutes after the failure.

At Missoula it was determined that the impeller did not penetrate its protective shroud, but some portion of the engine structure exited the engine intake, impacted the propeller, and was thrown into the side of the fuselage.

As this was the first reported operational failure of a TPE331 compressor impeller, the investigation focused on the failure mode of the impeller body. A metallurgical analysis completed by Allied-Signal Aerospace, under the supervision of the FAA, revealed that the impeller failed from a low cycle fatigue fracture mode initiating from multiple areas in the backface fillet. Further examination revealed numerous other cracks within the backface fillet area.

## Aircraft

- Registration: [N380PH](https://openairdocs.org/deregistered/N380PH-1997-09-11), registration cancelled 1997-09-11, S/N AC582 (OpenAirDocs)
- Reported make and model: FAIRCHILD SA227
- Registry model: [Fairchild SA227-AC](https://openairdocs.org/model/fairchild-sa227-ac) (registry code 3377509) (OpenAirDocs)
- Category: Airplane
- Serial number: AC582
- Airframe hours: 23955
- Engines: GARRETT TPE331-114 1000 horsepower turbo prop
- Damage: Minor damage
- Flight: Part 135
- Operator: Horizon Airlines
- Registered owner: First Security Bank Of Utah
- Airworthiness certificate: Standard, Transport
- Last inspection: Continuous airworthiness, November 6, 1994, 82 hours before
- Departed: HLN, HELENA, MT
- Destination: GEG, SPOKANE, WA
- Flight plan: IFR

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 31; commercial, airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--w/ waivers/lim; seat: left; flight hours: 7,900 total

## Weather

- Conditions: Dawn

## 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 19941117048559A](https://openairdocs.org/incident/19941117048559A), Nov 17, 1994: Swrngn SA227AC, Missoula, MT, Substantial damage. Lost engine en route. Diverted to mso. Internal failure but parts of impeller came out intake and struck fuselage.

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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