Serious incident Boeing 747-123 N157UA,
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ASN Wikibase Occurrence # 371177
 
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Date:Monday 2 May 1988
Time:19:16 LT
Type:Silhouette image of generic B741 model; specific model in this crash may look slightly different    
Boeing 747-123
Owner/operator:United Airlines
Registration: N157UA
MSN: 20106/79
Year of manufacture:1970
Total airframe hrs:39950 hours
Engine model:P&W JT9D-7A
Fatalities:Fatalities: 0 / Occupants: 258
Aircraft damage: Minor
Category:Serious incident
Location:Nr Tokyo, PO -   United States of America
Phase: En route
Nature:Passenger - Scheduled
Departure airport:Los Angeles International Airport, CA (LAX/KLAX)
Destination airport:Tokyo
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
UNITED FLT 97 EXPERIENCED INDICATIONS OF UNEVEN FUEL FLOW FROM MAIN TANKS 2 AND 3 AT FL360 BEGINNING ABOUT 4- HOURS AFTER DEPARTURE ON AN 11-HOUR TRANSPACIFIC FLIGHT. THE FUEL SYSTEM HAD BEEN SET UP FOR ALL ENGINE FEED FROM THE NOS 2 AND 3 TANKS. ALTHOUGH IT WAS LATER ESTABLISHED THAT THE NUMBER 2 CROSSFEED VALVE FAILED IN THE CLOSED POSITION, THE S/O INFORMED THE CAPT THAT THE INTRANSIT LIGHT HAD ILLUMINATED WHEN THE VALVE SELECTOR WAS MOVED TO THE CLOSED POSITION - INDICATING NORMAL CROSSFEED VALVE OPERATION. FUEL SYSTEM PROBLEM WAS MISDIAGNOSED AS A PROBLEM OF FAULTY FUEL GAGE INDICATIONS. FUEL MONITORING INDICATED INSUFFICIENT FUEL FLOW FROM NO 2 TANK WHEN CROSSFEEDING. ENGS 1, 3, AND 4 FLAMED OUT WHEN FUEL WAS EXPENDED FROM ALL TANKS EXCEPT NO 2. EMERGENCY DESCENT WAS MADE TO DESTINATION TOKYO-NARITA AIRPORT. CREW REPORTED THEY USED FLAPS-20, BUT DFDR SHOWED FLAPS-1 WAS USED FOR LANDING. 3 TIRES BLEW ON LANDING. ALL 3 FLIGHTCREW QUALIFIED IN THE B-747 IN THE 13-MONTHS BEFORE THE INCIDENT.

Probable Cause:

Accident investigation:
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Investigating agency: NTSB
Report number: DCA88IA056
Status: Investigation completed
Duration: 2 years 1 month
Download report: Final report

Sources:

NTSB DCA88IA056

Revision history:

Date/timeContributorUpdates
25-Mar-2024 18:48 ASN Update Bot Added

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