Aircraft Accident/Incident Report

Salt Lake City, Utah 84116
Saturday, January 11, 2003 MST

NTSB Narrative Summary Released at Completion of Accident

The passenger jet was at a cruise altitude of 37,000 feet msl and approximately 95 nautical miles south of Salt Lake City (SLC), when a flight attendant called from the aft cabin and stated there was a fire in the left aft lavatory, and that another flight attendant was fighting the active flames with a Halon extinguisher. The captain declared an emergency, requested priority handling for landing at SLC, and made an uneventful landing. An examination of the airplane revealed the lavatory toilet water level sensor was charred and melted. On further examination, the top left corner of the circuit board in the sensor was melted and consumed. Portions of several wires that had solder attachments to the circuit board at the melted area, including a 115-volt AC input wire and a 28-volt DC ground wire were melted and consumed. The left side of the circuit relay, adjacent to the consumed area of the circuit board, was melted and had melted solder on its exterior. The left hexagon-shaped screw, one of the two screws that mount the relay to the circuit board, was also melted. The manufacturer determined the melting point of the screw was between 2,550 and 2,650 degrees F. The investigation team determined that for these temperatures to occur, one of the wires in the area of the left screw would have had to arc.

NTSB Probable Cause Narrative

the arcing wires in the lavatory sensor that resulted in the subsequent fire.

Event Information

Type of Event Incident
Event Date 1/11/2003
Event Day of the Week Saturday
Time of Event 45
Event Time Zone Mountain Standard Time
Event City Salt Lake City
Event State UTAH
Event Country --
Zipcode of the event site 84116
Event Date Year 2003
Event Date Month 1
MidAir Collision Indicator No
On Ground Collision occurred ? No
Event Location Latitude 404718N
Event Location Longitude 1115934W
Event Location Airport --
Event Location Nearest Airport ID --
Indicates whether the acc/inc occurred off or on an airport Off Airport/Airstrip
Distance from airport in statute miles --
Degrees magnetic from airport --
Airport Elevation --
Weather Briefing Completeness Not pertinent
Investigator's weather source Weather Observation Facility
Time of the weather observation 56 Mountain Standard Time
Direction of event from weather observation facility (degrees) 360
Weather Observation Facility ID SLC
Elevation of weather observation facility 4227
Distance of event from weather observation facility (units?) 95
Time Zone of the weather observation MST
Lighting Conditions Night/Dark
Lowest Ceiling Height 7500
Lowest Non-Ceiling Height --
Sky/Lowest/Cloud Conditions --
Sky Condition for Lowest Ceiling Broken
Visibility Runway Visual Range (Feet) --
Visibility Runway Visual Value (Statute Miles) --
Visibility (Statute Miles) 0.25
Air Temperature at event time (in degrees celsius) 0
Dew Point at event time (in degress fahrenheit) 0
Wind Direction (degrees magnetic) --
Variable Wind Indicator --
Wind Speed (knots) --
Wind Velocity Indicator Calm
Wind Gust Indicator Not Gusting
Wind Gust (knots) --
Altimeter Setting at event time (in. Hg) 30.11
Density Altitude (feet) 3267
Intensity of Precipitation --
METAR weather report --
Event Highest Injury None
On Ground, Fatal Injuries --
On Ground, Minor Injuries --
On Ground, Serious Injuries --
Injury Total Fatal --
Injury Total Minor --
Injury Total None 140
Injury Total Serious --
Injury Total All --
Investigating Agency NTSB
NTSB Docket Number (internal use) 14220
NTSB Notification Source FAA COMM CTR
NTSB Notification Date Jan 13 2003 12:00AM
NTSB Notification Time 1500
Fiche Number and/or location -used to find docket information DMS
Date of most recent change to record Nov 25 2003 11:36AM
User who most recently changed record NTSB\MONR
Basic weather conditions Visual Meteorological Cond
FAA District Office Salt Lake City, UT FSDO

Aircraft Involved

Aircraft #1

Aircraft Registration Number N551UA
NTSB Number DEN03IA033
Missing Aircraft Indicator --
Federal Aviation Reg. Part Part 121: Air Carrier
Type of Flight Plan filed IFR
Flight plan Was Activated? Yes
Damage Minor
Aircraft Fire In-flight
Aircraft Explosion None
Aircraft Manufacturer's Full Name Boeing
Aircraft Model 757-222
Aircraft Series Identifier --
Aircraft Serial Number 25339
Certified Max Gross Weight 240000
Aircraft Category Airplane
Aircraft Registration Class U.S. Registered/U.S. Soil
Aircraft is a homebuilt? No
Flight Crew Seats --
Cabin Crew Seats --
Passenger Seats --
Total number of seats on the aircraft 190
Number of Engines 2
Fixed gear or retractable gear Retractable
Aircraft, Type of Last Inspection Continuous Airworthiness
Date of Last Inspection Nov 17 2002 12:00AM
Airframe hours since last inspection 568
Airframe Hours 41261
ELT Installed No
ELT Activated No
ELT Aided Location of Event Site No
ELT Type --
Aircraft Owner Name Wilmington Trust Company Trust
Aircraft Owner Street Address Rodney Square NO ATTN C
Aircraft Owner City Wilmington
Aircraft Owner State DE
Aircraft Owner Country USA
Aircraft Owner Zipcode 19890
Operator is an individual? No
Operator Name United Airlines
Operator Same as Owner? No
Operator Is Doing Business As --
Operator Address Same as Owner? No
Operator Street Address P. O. Box 66100
Operator City Chicago
Operator State IL
Operator Country USA
Operator Zip code 60666
Operator Code UALA
Owner has at least one certificate --
Other Operator of large aircraft? --
Certified for Part 133 or 137 Operation --
Operator Certificate Number --
Indicates whether an air carrier operation was scheduled or not Scheduled
Indicates Domestic or International Flight Domestic
Operator carrying Pax/Cargo/Mail Passenger Only
Type of Flying (Per_Bus / Primary) --
Second Pilot on Board Yes
Departure Point Same as Event No
Departure Airport Code SFO
Departure City San Francisco
Departure State CA
Departure Country USA
Departure Time 2228
Departure Time Zone MST
Destination Same as Local Flt --
Destination Airport Code BOS
Destination City Boston
Destination State MA
Destination Country USA
Specific Phase of Flight Cruise
Report sent to ICAO? No
Evacuation occurred No
Date of most recent change to record Aug 21 2003 12:21PM
User who most recently changed record MCBM
Since inspection or accident Time of Accident
Event Location Runway Number and Location --
Runway Length --
Runway Width --
Sight Seeing flight No
Air Medical Flight No
Medical Flight --