Incident Overview

Date: Saturday 21 February 2004
Aircraft Type: Boeing 737-59D
Owner/operator: bmibaby
Registration Number: G-BVKC
Location: Cardiff-Wales Airport (CWL) – ÿ United Kingdom
Phase of Flight: Landing
Status: Substantial, repaired
Casualties: Fatalities: 0 / Occupants: 120
Component Affected: Left Main Landing Gear (MLG)Left Main Landing Gear (MLG)
Investigating Agency: AAIBAAIB
Category: Accident
A left main landing gear (MLG) experienced a violent shimmy oscillation after wheel brakes were applied, leading to a fracture of the lower torsion link. The shimmying persisted with increased braking, causing further damage to the MLG, tyre, and brake. This resulted in steering difficulties and structural oscillatory loads on the aircraft.A left main landing gear (MLG) experienced a violent shimmy oscillation after wheel brakes were applied, leading to a fracture of the lower torsion link. The shimmying persisted with increased braking, causing further damage to the MLG, tyre, and brake. This resulted in steering difficulties and structural oscillatory loads on the aircraft.

Description

The left main landing gear (MLG) began a violent shimmy (yaw oscillation) when the wheelbrakes were applied after a normal landing touchdown, probably damaging the MLG lower torsion link. The shimmying stopped when braking was reduced but restarted when braking was increased, causing the torsion link to fracture. Further higher amplitude shimmying of the left MLG ensued, resulting in severe MLG tyre, wheel and brake damage and substantial oscillatory loads on the aircraft structure. Steering difficulties were experienced during both shimmying episodes. It was likely that the shimmying resulted from excessive wear of the torsion link apex joint that reduced the effectiveness of the shimmy damper. Maintenance records indicated that the MLG had been maintained in accordance with the manufacturer’s recommendations, but it was considered that relevant Aircraft Maintenance Manual (AMM) procedures could be difficult to follow.

Primary Cause

Excessive wear of the torsion link apex joint reduced the effectiveness of the shimmy damper, contributing to the shimmying oscillation.Excessive wear of the torsion link apex joint reduced the effectiveness of the shimmy damper, contributing to the shimmying oscillation.

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