# NTSB LAX90IA305: Boeing 747-422, N174UA, Los Angeles, CA, August 27, 1990

- Type: NTSB incident investigation
- Classification: Incident · Minor injuries · Incident investigation · Final report
- Date: August 27, 1990, 10:25 local (17:25 UTC)
- Place: Los Angeles, CA
- Coordinates: 33.950046, -118.400817 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=33.9500&lon=-118.4008&mi=10
- Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 25 minor, 320 uninjured; on the ground: 2 minor
- Status: Completed, report December 30, 1992
- Report: Approved by Office Director
- NTSB case key (mKey): 26662
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX90IA305
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/26662/pdf
- Page: https://openairdocs.org/ntsb/LAX90IA305

## Probable cause

THE FAILURE OF THE MANUFACTURER TO ENSURE THAT THE LANDING GEAR SELECTOR VALVES AND THEIR ASSOCIATED DRUM LINK ASSEMBLIES WERE PROPERLY INSTALLED PRIOR TO DELIVERY OF THE AIRCRAFT. A FACTOR IN THE ACCIDENT WAS THE LACK OF INFORMATION AVAILABLE TO THE CREW CONCERNING THE SECONDARY ALTERNATE GEAR EXTENSION PROCDURE.

## Sequence of events

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

- Gear not extended, landing - roll
  - landing gear,gear lever - disconnected (cause)
  - maintenance,installation - improper, manufacturer (cause)
  - gear extension - not possible, pilot in command
  - information unavailable, pilot in command (contributing factor)

## Analysis

THE CREW NOTED THAT THE NOSE AND MAIN BODY GEAR INDICATED UP AND LOCKED AFTER NORMAL GEAR EXTENSION. THE CREW USED THE ALT GEAR EXTENSION PROCEDURE, WHICH WAS UNSUCCESSFUL. THE AIRCRAFT LANDED WITH THE NOSE AND MAIN BODY GEAR RETRACTED WHEN THE FLIGHT REACHED THE MIN FUEL STATE. EXAM OF THE AIRCRAFT REVEALED THAT THE SELECTOR VALVE FOR THE AFFECTED GEAR WAS IN THE UP AND LOCKED POSITION, AND THE BOLT WHICH CONNECTS THE VALVE ARM TO THE COCKPIT CONTROL CABLE SYSTEM WAS MISSING. THE BOLT FOR WING GEAR SELECTOR VALVE ARM WAS FOUND PARTIALLY BACKED OUT; THE NUT AND COTTER PIN WERE MISSING. THE AIRCRAFT WAS DELIVERED TO UNITED IN JAN OF 1990 AND HAD 2,952 FLT HRS AND 402 CYCLES. DETAILED REVIEW OF THE MAINT RECORDS PROVED THAT UNITED HAD NOT PERFORMED ANY MAINT ON THE LANDING GEAR SYSTEM. A SECOND ALT GEAR EXTENSION PROCEDURE INVOLVING DE-ENERGIZING THE HYDRAULIC SYSTEM FOR THE AFFECTED GEAR IS NOT PUBLISHED IN THE CREW MANUALS, TAUGHT DURING INITIAL TRAINING, NOR AVAILABLE ON ANY CHECKLIST.

## Aircraft

- Registration: [N174UA](https://openairdocs.org/deregistered/N174UA-2018-05-17), registration cancelled 2018-05-17, S/N 24381, built 1990 (OpenAirDocs)
- Reported make and model: BOEING 747-422
- Registry model: [Boeing 747-422](https://openairdocs.org/model/boeing-747-422) (registry code 1384935) (OpenAirDocs)
- Registry engine: [Pratt & Whitney PW4000 series](https://openairdocs.org/engine/pratt-whitney-pw4000-series) (registry code 52119, turbo-fan) (OpenAirDocs)
- Category: Airplane
- Serial number: 24381
- Airframe hours: 2952
- Engines: P&W JT 4056 56000 lbs thrust turbo fan
- Damage: Minor damage
- Flight: Part 121
- Operator: United Airlines
- Registered owner: Unknown
- Airworthiness certificate: Standard, Transport
- Last inspection: Continuous airworthiness, August 25, 1990, 31 hours before
- Departed: ASSY, SYDNEY, OF
- Destination: LAX
- Flight plan: IFR
- Airport: LAX, Los Angeles Intl., runway 25R, 12,091 × 150 ft, concrete

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 57; airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; flight hours: 18,795 total, 25 in this make and model, 121 in the last 90 days, 42 in the last 30 days, 13 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 250° at 10 knots
- Visibility: 12 statute miles
- Lowest ceiling: none
- Temperature: 75 °F, dew point 55 °F
- Altimeter: 30.00 inHg
- Observed at: LAX

## 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 19900827040239I](https://openairdocs.org/incident/19900827040239I), Aug 27, 1990: Boeing 747422, Los Angeles, CA, Minor damage. Landed with nose and both body gears retracted. Passengers evacuated on runway.

## Other investigations on N174UA (1)

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.

- [NTSB WPR13LA131](https://openairdocs.org/ntsb/WPR13LA131), Feb 19, 2013: Boeing 747-422 (N174UA), Pacific Ocean, A1, no damage. Probable cause: The flight’s encounter with moderate clear air turbulence while en route, which resulted in a serious injury to a flight attendant. Contributing to the accident was the lack of communication…

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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