# NTSB ANC89FA069: Bell 412, N524EH, Girdwood, AK, May 6, 1989

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Field investigation · Final report
- Date: May 6, 1989, 12:38 local (20:38 UTC)
- Place: Girdwood, AK
- Coordinates: 60.899848, -148.910263 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=60.8998&lon=-148.9103&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 2 minor
- Status: Completed, report August 2, 1990
- Report: Approved by Office Director
- NTSB office: Alaska Regional Office
- NTSB case key (mKey): 5106
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC89FA069
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/5106/pdf
- Page: https://openairdocs.org/ntsb/ANC89FA069

## Probable cause

A MAIN ROTOR FLIGHT CONTROL BOLT (PART NUMBER 20-057-6-38D) CAME OUT OF ITS ROD END BEARING WHILE IN FLIGHT DUE TO THE BOLT BEING IMPROPERLY TORQUED DURING MAINTENANCE.

## Sequence of events

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

- Airframe/component/system failure/malfunction, cruise - normal
  - rotorcraft flight control,cyclic control - disconnected (cause)
  - maintenance - improper, other maintenance personnel (cause)
- Forced landing, descent - emergency
  - terrain condition - mountainous/hilly (contributing factor)

## Analysis

WHILE IFR AT 10,000 FEET OVER MOUNTAINOUS TERRAIN, THE HELCIOPTER EXPERIENCED VIOLENT VERTICAL VIBRATIONS, WHICH CONTINUED UNTIL THE CRASH-LANDING ABOUT FIVE MINUTES LATER. ON BOARD WEATHER RADAR WAS USED TO GUIDE THE HELICOPTER AROUND THE MOUNTAIN TOPS, WHICH WERE IN THE CLOUDS. AT ABOUT 200 FEET ABOVE THE GROUND, THE HELICOPTER CAUGHT FIRE, TAIL ROTOR CONTROL WAS LOST, BOTH ENGINES QUIT, AND CYCLIC CONTROL BECAME UNRESPONSIVE. THE HELICOPTER WAS DESTROYED BY POST-CRASH FIRE. ABOUT ONE HOUR OF FLT TIME EARLIER, THE HELICOPTER HAD UNDERGONE AN INSPECTION, DURING WHICH THE MAIN ROTOR FLIGHT CONTROL SYSTEM BOLTS HAD BEEN RETORQUED. ALL BUT ONE OF THESE BOLTS WERE FOUND IN THE WRECKAGE. HOWEVER, THE ROD END FOR THE MISSING BOLT WAS FOUND.

## Aircraft

- Registration: [N524EH](https://openairdocs.org/deregistered/N524EH-1991-12-12), registration cancelled 1991-12-12, S/N 33069 (OpenAirDocs)
- Reported make and model: BELL 412
- Registry model: [Bell 412](https://openairdocs.org/model/bell-412) (registry code 1182202) (OpenAirDocs)
- Category: Helicopter
- Serial number: 33069
- Airframe hours: 3578
- Engines: P&W PT6T-3B 1025 horsepower turbo shaft
- Damage: Destroyed
- Fire: In-Flight
- Flight: Part 135
- Registered owner: Era Aviation, Inc.
- Airworthiness certificate: Standard, Normal
- Last inspection: Continuous airworthiness, May 4, 1989, 1 hours before
- Departed: VDZ, VALDEZ, AK
- Destination: ANC, ANCHORAGE, AK
- Flight plan: IFR

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 45; airline transport, commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: helicopter, airplane; medical: class 2, valid medical--no waivers/lim.; seat: right; toxicology performed; flight hours: 9,300 total, 1,700 in this make and model, 8,700 as pilot in command, 6 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 40° at 4 knots
- Visibility: 60 statute miles
- Lowest ceiling: 5,500 ft broken
- Temperature: 46 °F
- Altimeter: 29.00 inHg
- Observed at: ANC, 37 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 19890506010839A](https://openairdocs.org/incident/19890506010839A), May 6, 1989: Bell 412, Girdwood, AK, Destroyed. Severe vibration en route causing damage. Autorotated. Lost cyclic. Engine quit. Landed in turn. Rotor bolt missing

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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