# NTSB DCA93MA033: Boeing 747-121, N473EV, Anchorage, AK, March 31, 1993

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Class 1 · Major · Final report
- Date: March 31, 1993, 12:34 local (16:34 UTC)
- Place: Anchorage, AK
- Coordinates: 61.159198, -149.990325 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=61.1592&lon=-149.9903&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 5 uninjured
- Status: Completed, report May 10, 1994
- Report: Board-adopted at Board Meeting
- Investigation class: Class 1
- NTSB office: Major Investigations Division
- Safety recommendations: Yes
- NTSB case key (mKey): 10973
- NTSB case page: https://www.ntsb.gov/investigations/Pages/DCA93MA033.aspx
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/10973/pdf
- Board report AAR9306 (PDF): https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR9306.pdf
- Page: https://openairdocs.org/ntsb/DCA93MA033

## Probable cause

THE LATERAL SEPARATION OF THE NO. 2 ENGINE PYLON DUE TO AN ENCOUNTER WITH SEVERE OR POSSIBLY EXTREME TURBULENCE THAT RESULTED IN DYNAMIC MULTI-AXIS LATERAL LOADINGS THAT EXCEEDED THE ULTIMATE LATERAL LOAD-CARRYING CAPABILITY OF THE PYLON, WHICH WAS ALREADY REDUCED BY THE PRESENCE OF THE FATIGUE CRACK NEAR THE FORWARD END OF THE PYLON'S FORWARD FIREWALL WEB.

## Sequence of events

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

- In flight encounter with weather, climb - to cruise
  - weather condition - mountain wave (cause)
  - weather condition - turbulence (cause)
- Engine tearaway, climb - to cruise
  - nacelle/pylon - fatigue (contributing factor)
  - nacelle/pylon - failure,total (cause)
  - nacelle/pylon - separation (cause)
  - 1 engine - separation

## Analysis

SHORTLY AFTER TAKEOFF FROM ANCHORAGE, THE AIRPLANE FLEW INTO AN AREA OF SEVERE TURBULENCE, WHILE CLIMBING THROUGH AN ALTITUDE OF ABOUT 2000 FEET.  THE NUMBER 2 ENGINE AND ENGINE PYLON SEPARATED FROM THE AIRPLANE.  THE FLIGHTCREW DECLARED AN EMERGENCY AND THE FLIGHT RETURN TO ANCHORAGE, WHERE AN UNEVENTFUL LANDING WAS ACCOMPLISHED.  THE INVESTIGATION REVEALED THAT A STRONG EASTERLY WIND INTERACTED WITH MOUNTAINS EAST OF ANCHORAGE, WHICH PRODUCED MOUNTAIN WAVE ACTIVITY.  THE AIRCRAFT ENCOUNTERED SEVERE OR POSSIBLY EXTREME TURBULENCE.  THERE WAS EVIDENCE THAT THIS RESULTED IN DYNAMIC MULTI-AXIS LATERAL LOADINGS THAT EXCEEDED THE ULTIMATE LATERAL LOAD-CARRYING CAPABILITY OF THE NUMBER 2 ENGINE PYLON, WHICH HAD ALREADY BEEN REDUCED BY THE PRESENCE OF A FATIGUE CRACK NEAR THE FORWARD END OF THE PYLON'S FORWARD FIREWALL WEB.

## Factual narrative

SEE NTSB BLUE COVER AVIATION ACCIDENT REPORT AAR-93-06 FOR FURTHER INFORMATION.

## Aircraft

- Registration: [N473EV](https://openairdocs.org/deregistered/N473EV-2011-07-01), registration cancelled 2011-07-01, S/N 19657, built 1970 (OpenAirDocs)
- Reported make and model: BOEING 747-121
- Registry model: [Boeing 747-121](https://openairdocs.org/model/boeing-747-121) (registry code 1384871) (OpenAirDocs)
- Registry engine: [Pratt & Whitney JT9D-3A](https://openairdocs.org/engine/pratt-whitney-jt9d-3a) (registry code 52050, turbo-fan) (OpenAirDocs)
- Category: Airplane
- Serial number: 19657
- Airframe hours: 18370
- Engines: P&W JT9D-7D 45500 lbs thrust turbo fan
- Damage: Substantial damage
- Flight: Part 129
- Operator: Japan Airlines
- Registered owner: Evergreen International
- Last inspection: Continuous airworthiness, March 3, 1993, 48 hours before
- Departed: ANC
- Destination: ORD, CHICAGO, IL
- Flight plan: IFR
- Airport: ANC, Anchorage Intl, runway 6R, 10,897 × 150 ft

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 42; commercial, airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: helicopter, airplane; medical: class 1, valid medical--w/ waivers/lim; seat: left; flight hours: 10,000 total, 750 in this make and model, 8,000 as pilot in command, 138 in the last 90 days, 61 in the last 30 days

## Weather

- Conditions: Visual (VMC), Day
- Wind: 90° at 7 knots
- Visibility: 60 statute miles
- Lowest ceiling: 8,000 ft overcast
- Temperature: 48 °F, dew point 21 °F
- Altimeter: 29.00 inHg
- Observed at: ANC

## 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 19930331007479A](https://openairdocs.org/incident/19930331007479A), Mar 31, 1993: Boeing 747121, Anchorage, AK, Substantial damage. Engine fell off in severe turbulence on climbout. Pylon failed due stress and fatigue crack. Wind shear reported.

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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