British Airways A319 at Manchester on Oct 19th 2016, nose wheel steering fault
Last Update: June 9, 2017 / 14:09:13 GMT/Zulu time
The aircraft was disabled, runway 23R needed to be closed until the aircraft could be towed to the apron.
The airline reported there was a nose wheel steering problem, the occurrence is being investigated by the AAIB.
On Oct 27th 2016 the AAIB indicated that the nose gear turned through 90 degrees to the right during the landing roll. The occurrence was rated an accident and is being investigated.
On Nov 15th 2016 the AAIB reported the nose gear torque link had separated on landing in Manchester.
On Jun 9th 2017 the AAIB released their bulletin concluding:
The detachment of the NLG torque link apex pin was most probably caused by damage sustained to the torque link apex pin nut locking components due to contact with a towbarless tractor. A Service Bulletin is available to replace the torque link apex pin assembly with a new design, intended to reduce the risk of contact damage with towbarles
The AAIB analysed:
Assessment of the recovered components from G-EUPM’s NLG indicates that the torque links separated because the apex pin released from the torque links after the apex pin nut had unscrewed and detached from the apex pin. The close proximity of the recovered apex pin and nut to the aircraft shows that once the apex pin had released, the nosewheels rapidly rotated to an extreme left angle.
The apex pin nut was able to unscrew because the locking bolt became detached from the apex pin nut prior to the landing at Manchester, although it is uncertain when this occurred. The occurrence of NLG shimmy on landing during the sector preceding the incident flight, and during takeoff and landing on the incident flight, is consistent with a loss of apex pin nut torque at least one flight prior to the inc ident flight.
Witness marks in the apex pin nut sealant show that the lock bolt, washer, castellated nut and cotter pin had been correctly assembled prior to the sealant application. The available evidence shows that this occurred during the 1C maintenance check in February 2016, 1,323 flight cycles prior to the torque link separation.
The cotter pin had been installed in the lock bolt in accordance with the AMM ‘Second Procedure’, with the head of the cotter pin oriented outboard. The missing area of sealant on the apex pin nut was in the same position as where the head of the cotter pin had been. The torn edges of this area of missing sealant indicate that it had detached in service, after the sealant had been applied and cured.
Similar sealant damage was observed on five other A320-series aircraft in the operator’s fleet, from a sample of 34 aircraft; such sealant damage is most likely caused by contact with the left paddle of a TBL tractor during pushback and towing operations. In addition, nine out of eleven of the operator’s TBL tractors had impact witness marks on the left paddle, adjacent to the position where the apex pin nut sits when the tractor is engaged with A320-series aircraft, further indicating that paddle contacts are occurring in routine operation.
Therefore, it is probable that contact with the left paddle of a TBL tractor damaged the sealant and the lock bolt cotter pin, castellated nut or lock bolt itself, leading to their subsequent detachment from the apex pin nut. This led to the eventual release of apex pin from the NLG torque links.
Previous occurrences of damage to apex pin nuts and locking bolts prompted the aircraft manufacturer to modify the design of the apex pin nut, with the narrower apex pin components becoming available in June 2012.
This article is published under license from Avherald.com. © of text by Avherald.com.
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