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AD/A330/46 - Nose Landing Gear Hydraulic Control Block
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AD/A330/46 - Nose Landing Gear Hydraulic Control Block
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| AD/A330/46 | Nose Landing Gear Hydraulic Control Block | 3/2005 |
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| Applicability: | AIRBUS A330-200 and A330-300 aircraft series, all serial numbers, except aircraft on which AIRBUS modification 50650 has been embodied in production or AIRBUS Service Bulletin (SB) A330-32-3156 has been embodied in service. |
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| Requirement: | Modify the Hydraulic Control Block (HCB) Part Number (PN) C24856000-9 and PN C24856001-7 in accordance with instructions given in AIRBUS SB A330-32-3156.Note 1: At the end of this modification:- the HCB PN C24856000-9 will become PN C24856000-11 and- the HCB PN C24856001-7 will become PN C24856001-9.Note 2: DGAC AD F-2005-016 EASA approval 2005-499 dated 12 January 2005 refers. |
| Compliance: | Not later than 30 September 2007. |
| This Airworthiness Directive becomes effective on 17 March 2005. | |
| Background: | An aircraft experienced a sudden veering during take-off roll at 47kts. Analysis of the flight data showed a “Braking and Steering Control Unit (BSCU) Channel 1 Fault” followed by a loss of Nose Wheel Steering (NWS). A brief 'hydraulic lock' occurred in the HCB preventing the transfer from steering to castoring mode and the nose gear returning to its straight-ahead position. Not corrected, the “hydraulic lock” combined with environmental effects, airport geometry and speed can lead to a hazardous event. In order to avoid this situation, AIRBUS and the suppliers have reviewed the design of the HCB by adding a check valve between the selector valve and the servo valve. This check valve limits the back pressure generated from torque applied to the gear due to ground movements in a free castor situation and would allow a nominal functioning of the bypass valve. The aim of this Directive is to require the installation of this check valve on the affected HCB. |
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James Coyne
Delegate of the Civil Aviation Safety Authority
4 February 2005