Back to home pageOE-IAG 737-400F MLG Torsion Link Failure on landing

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On 4 Oct 2016 at 04:55z, an ASL Airlines (in TNT Express livery), 737-400F, OE-IAG, 25168/2210, suffered a partial right hand main landing-gear failure, following a normal approach and landing on Runway 25 at Belfast Aldergrove (EGAA) in benign weather conditions.

On landing, an intense vibration developed, the crew cancelled the automatic brakes and thrust reversers, as there was sufficient runway, and the aircraft came to a stop. The lower torsion link was found to have fractured on the right main landing gear (MLG) possibly due to excessive MLG vibration (shimmy). The cause of the vibration could not be established but may have been related to the speed of the aircraft on landing, and possibly a problem with the shimmy damper or freeplay within the joints associated with the upper and lower torsion links.

The AAIB concluded that: The physical and recorded evidence indicate that the fracture to the lower torsion link on the right MLG leg was most likely caused by shimmy. This and previous occurrences show that the Boeing 737 MLG is susceptible to shimmy, particularly at higher landing speeds and for softer landings.

There was no evidence of a pre-existing defect in the failed torsion link or the apex joint which would have caused the shimmy. It was not possible to assess the condition of the shimmy damper or determine if there was any freeplay in the joints associated with the torsion links. Accordingly it is possible that there was a failure of the damper or excessive freeplay in the joints, which combined with the high-speed landing may have induced shimmy.

Whilst there was no evidence to suggest that maintenance was a causal or contributory factor, the manufacturer is currently working with the operator to assess the maintenance requirements to ensure they are appropriate for its operations.

The full AAIB report is available here

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*** Updated 18 Apr 2019 ***

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The fractured torsion link (courtesy of QinetiQ)

EGAA 040450Z 13009KT CAVOK 12/09 Q1027

This is another in a series of 737 Classic MLG failures:

  • 4 Oct 2016 - OE-IAG, ASL Airlines, Belfast
  • 12 Sep 2016 - 737-300SF, PK-YSY, Trigana Air Service MLG collapse on landing at WAVV, Wamena, Indonesia.
  • 26 Nov 2015 - XA-UNM 737-300 Gear collapse on landing at Mexico City-Benito Juárez
  • 22 Nov 2015 - EX-37005 737-300 Gear collapse on landing at Osh
  • 26 Oct 2015 - ZS-OAA, 737-400, Comair, Johannesburg, South Africa
  • 24 Oct 2015 - Peruvian Airlines 737-300 OB-2040-P MLG collapse on landing at Cusco
  • 28 Aug 2015 - 737-300CF, PK-BBY Cardig Air, MLG collapse in a landing accident at Wamena Airport (WMX), Indonesia.
  • 29 Apr 2014 - EI-STD, Air Contractors B737-400 MLG failure on landing at East Midlands
  • 7 Nov 2014 - Ariana Boeing 737-400, YA-PIE right MLG failure on landing.
  • 26 Jan 2014 - ZK-TLC, 737-300SF, Pacific Air Express, MLG collapse on landing at Honiara, Solomon Islands
  • 11 Feb 2013, AP-BEH, 737-300, Pakistan International Airlines, Muscat-Seeb, Oman

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