# NTSB ANC89FA034: Beech BE-99, Fort Yukon, AK, January 13, 1989

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Field investigation · Final report
- Date: January 13, 1989, 17:12 local (21:12 UTC)
- Place: Fort Yukon, AK
- Coordinates: 66.560501, -145.250137 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=66.5605&lon=-145.2501&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 2 uninjured
- Status: Completed, report May 22, 1990
- Report: Approved by Office Director
- NTSB office: Alaska Regional Office
- NTSB case key (mKey): 5098
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC89FA034
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/5098/pdf
- Page: https://openairdocs.org/ntsb/ANC89FA034

## Probable cause

THE SEPARATION OF A SINGLE PROPELLER BLADE WHICH CAUSED THE DOWNWARD AND REARWARD DISPLACEMENT OF THE NUMBER TWO ENGINE.

## Analysis

DURING CRUISE FLIGHT AT 8000 FEET ABOVE MEAN SEA LEVEL THE CO-PILOT NOTICED A 100 POUND TORQUE INCREASE ON THE NUMBER TWO ENGINE. DURING HIS ATTEMPT TO REDUCE THE TORQUE HE HEARD AN EXPLOSION, SAW SPARKS COME FROM THE NUMBER TWO ENGINE EXHAUST STACKS AND OBSERVED A SLOW TURNING PROPELLER AS THE ENTIRE ENGINE NACELLE DISAPPEARED BENEATH THE AIRPLANE. FULL POWER ON THE NUMBER ONE ENGINE ALLOWED THE CREW TO REDUCE THE RATE OF DESCENT TO 1,500 FOOT PER MINUTE AND THEY CRASH LANDED ON THE FROZEN RIVER. ON SITE EXAMINATION REVEALED ONE PROPELLER BLADE FROM THE NUMBER TWO ENGINE WAS MISSING AND THAT THE NUMBER TWO ENGINE HAD SEPARATED DURING THE IMPACT SEQUENCE. SUBSEQUENT METALLURGICAL EXAMINATION SHOWED A FATIGUE FRACTURE ON THE REMAINING STUB OF THE MISSING BLADE.

## Sequence of events

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

- Airframe/component/system failure/malfunction, cruise - normal
  - propeller system/accessories,blade - fatigue (cause)
  - propeller system/accessories,blade - separation (cause)
- Forced landing, descent - emergency
- In flight collision with terrain/water, landing - flare/touchdown
  - 1 engine - separation
  - wheels up landing - intentional

## Aircraft

- Registration: CFBCH (not matched to a registry record)
- Reported make and model: BEECH BE-99
- Category: Airplane
- Serial number: U162
- Airframe hours: 20967
- Engines: P&W PT6A-27 680 horsepower turbo prop
- Damage: Substantial damage
- Flight: Part 129
- Registered owner: Aklak Air Ltd
- Airworthiness certificate: Standard, Normal
- Last inspection: 100 hour, December 10, 1988, 50 hours before
- Departed: INUVIK
- Destination: FAI, FAIRBANKS, AK
- Flight plan: IFR

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 39; airline transport; airplane ratings: multi-engine land, multi-engine sea, single-engine land; instrument ratings: airplane; medical: class 1, valid medical--w/ waivers/lim; seat: left; flight hours: 4,350 total, 4,300 as pilot in command, 75 in the last 90 days, 5 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Night/bright
- Wind: 30° at 3 knots, gusting 17
- Visibility: 15 statute miles
- Lowest ceiling: none
- Temperature: 39 °F, dew point 48 °F
- Observed at: FYU, 17 nm away

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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