# NTSB LAX89LA068: Boeing 747SP-21, N146UA, Midway Islands (Pacific Ocean), December 23, 1988

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Limited investigation · Final report
- Date: December 23, 1988, 00:30 local (10:30 UTC)
- Place: Midway Islands (Pacific Ocean)
- Coordinates: 37.635818, -130.070388 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=37.6358&lon=-130.0704&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: Serious injuries
- Injuries: 1 serious, 1 minor, 220 uninjured
- Status: Completed, report July 9, 1990
- Report: Approved by Office Director
- NTSB case key (mKey): 26312
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX89LA068
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/26312/pdf
- Page: https://openairdocs.org/ntsb/LAX89LA068

## Probable cause

AIRCRAFT'S ENCOUNTER WITH UNFORECAST SEVERVE CLEAR TURBULENCE.

## Sequence of events

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

- In flight encounter with weather, cruise - normal
  - weather condition - turbulence,clear air (cause)
  - meteorological service - inadequate, other person (contributing factor)
  - seat belt sign - not used (contributing factor)
  - seat belt - not used (contributing factor)

## Analysis

UNITED AIRLINES FLT 820 WAS ENRTE FROM NORITA, JAPAN TO SAN FRANCISCO, CA. AT FLT LVL 380 SEVERE CLEAR AIR TURBULENCE WAS ENCOUNTERED. THREE CABIN CREW MEMBERS WERE THROWN TO THE CEILING, TWO OF WHOM WERE INJURED, ONE SUSTAINING A FRACTURED LEG. THE FLT DIVERTED TO HONOLULU AND LANDED WITHOUT INCIDENT. BOTH FLT AND CABIN CREW REPORTED THAT THERE HAD BEEN NO WARNING OF ANY IMPENDING TURBULENCE PRIOR TO ABRUPTLY ENCOUNTERING THE TURBULENCE THAT CAUSED THE INJURIES, AND THAT THE SEAT BELT SIGN WAS TURNED OFF.

## Aircraft

- Registration: [N146UA](https://openairdocs.org/deregistered/N146UA-2001-08-23), registration cancelled 2001-08-23, S/N 21547 (OpenAirDocs)
- Reported make and model: BOEING 747SP-21
- Registry model: [Boeing 747SP-21](https://openairdocs.org/model/boeing-747sp-21) (registry code 1384802) (OpenAirDocs)
- Category: Airplane
- Serial number: 21547
- Engines: P&W JT-9D 40000 lbs thrust turbo fan
- Damage: No damage
- Flight: Part 121
- Operator: United Airlines
- Registered owner: Banker'S Trust Co.
- Airworthiness certificate: Standard, Transport
- Departed: NRT, NORITA, OF
- Destination: SFO, SAN FRANCISCO, CA
- Flight plan: IFR
- Airport: NONE

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 60; airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: left; flight hours: 22,735 total, 810 in this make and model, 40 in the last 90 days, 13 in the last 24 hours

## Weather

- Conditions: Dawn
- Visibility: 50 statute miles
- Lowest ceiling: none
- Temperature: 50 °F
- Altimeter: 29.00 inHg

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Incident 19881223056109I](https://openairdocs.org/incident/19881223056109I), Dec 23, 1988: Boeing 747SP21, Honolulu, HI. 2 Flight attendants sustained injuries when aircraft encountered turbulence. Received medical help after landing.

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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