Event Details

Title:Uncommanded roll, Boeing 737-236, G-BKYI
Micro summary:This Boeing 737-236 experienced uncommanded roll coincident with flap selection.
Event Time:1996-11-08 at 0820 UTC
File Name:1996-11-08-UK.pdf
Publishing Agency:Aircraft Accident Investigation Board (AAIB)
Publishing Country:United Kingdom
Report number:EW/C96/11/3
Site of event:Approach to RWY 27 L
Departure:Jersey Airport, Jersey, Channel Islands
Destination:London Heathrow Airport, London, England
Airplane Type(s):Boeing 737-236
Flight Phase:Approach
Operator(s):British Airways
Type of flight:Revenue
Serious Injuries:0
Other Injuries:0
Executive Summary:The aircraft was inbound to London Heathrow on a scheduled flight from Jersey. While fully established on the approach for Runway 27L, the aircraft encountered two separate uncommanded roll events. The first was with flap 5 selected, followed by a more pronounced event almost coincident with the flap 25 selection. In both cases the aircraft rolled in a gentle but positive manner. The crew considered that the roll force was very smooth and quite strong, with no detected rudder or yaw damper movement. The crew commented that the rolling motion was not characteristic of any previously experienced wake vortex encounters.

The commander, who was the handling pilot, initiated a go-around and transmitted a PAN call to ATC advising of a flight control problem. The possibility of a flap asymmetry was considered, but there was no indication of such an asymmetry on the flap indicator. A handling check was performed by decelerating the aircraft to an approach/manoeuvring speed of 150 kt with 15 flap. No abnormalities were noted by the crew, so radar vectoring was accepted for a left hand pattern to reposition for a further ILS approach whilst maintaining the established 15 flap landing configuration. The autopilot was engaged after the go-around and maintained until about 700 feet on final approach, followed by an uneventful manual landing by the First Officer.

The London Heathrow METAR for 0820 hrs gave the surface wind as 170/2 kt, visibility 18 km, few/scattered cloud base 6,000 feet. The temperature was +3.6C and dew point +1.5C, the QNH was 1023 mb.
Learning Keywords:Operations - Upset - Uncommanded or excessive Roll
Operations - Upset - Wake vortex/jet blast
Systems - Flight Controls - Spoilers - Slats - Flaps


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