United B763 at London on Apr 29th 2019, smoke in cabin

Last Update: October 10, 2019 / 15:07:33 GMT/Zulu time

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Incident Facts

Date of incident
Apr 29, 2019

Classification
Report

Airline
United

Flight number
UA-929

Aircraft Registration
N657UA

Aircraft Type
Boeing 767-300

ICAO Type Designator
B763

A United Boeing 767-300, registration N657UA performing flight UA-929 from London Heathrow,EN (UK) to Chicago O'Hare,IL (USA) with 86 passengers and 11 crew, was climbing through 15,000 feet out of London when passengers observed a momentary flash above the overhead ceiling panels near seat row 20 followed by smoke and a burning odour. Cabin crew informed the flight crew, who declared PAN PAN and decided to return to London Heathrow. The crew worked the fumes and smoke checklists, which involved selecting the utility bus switches to OFF, cabin crew subsequently reported that smoke and haze dispersed, the odour was still noticeable but dissipating. The aircraft stopped the climb at FL290 and landed safely back on Heathrow's runway 09L 43 minutes after departure.

On Oct 10th 2019 the UK AAIB released their bulletin concluding the probable cause of the serious incident was:

Damage to the harness was found to have been caused by an unidentified electrical event between two of the insulated wires within the harness. The electrical event led to arcing between the wires which generated significant heat, enough to cause localised melting of the copper strands in the wires. The exact nature of this event could not be determined.

The AAIB wrote: "The operator carried out an examination of the area and identified the source of the smoke and haze. Wiring in the cabin ceiling lighting harness above Row 19/20 on the left side showed evidence of electrical arcing and heat damage. There was also soot on the insulation surrounding a section of wiring, as shown in Figure 1. The circuit breaker (CB) protecting the circuit was found to have tripped. The wiring harness, CB and the lighting ballast connected to the harness were removed for further examination by the manufacturer. The CB and lighting ballast passed functional tests."
Incident Facts

Date of incident
Apr 29, 2019

Classification
Report

Airline
United

Flight number
UA-929

Aircraft Registration
N657UA

Aircraft Type
Boeing 767-300

ICAO Type Designator
B763

This article is published under license from Avherald.com. © of text by Avherald.com.
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