Document ID: chunk:federal_register_of_legislation:F2009L03260:body:0:p2
Version: federal_register_of_legislation:F2009L03260
Segment Type: other
Provision Reference: 
Character Range: 2834–5444

by the amount of wear found, as defined in the SB.

             For Requirement 3 - Before next flight.

             For Requirement 4 - Within 24 months after the effective date of this AD.

             For Requirement 5 - After 20 August 2011.
             This Airworthiness Directive becomes effective on 24 September 2009.
Background:  During 1995, several reports were received of brake QD couplings loosened and/or disconnected during operation.  In a few cases, residual brake pressure was trapped in the affected brake, causing asymmetric braking and/or resulting in hot brakes.  Loosened couplings may cause a hydraulic leak with the risk of a brake fire.  Investigation revealed that the installation of the brake QD couplings must be done with care and that the locking teeth on the light alloy sleeve are prone to wear.  The Fokker 70/100 Aircraft Maintenance Manual (AMM) has been revised to include additional information to ensure correct removal and installation of the couplings.

             In 1997, Fokker Services issued SBF100-32-106, recommending the introduction of QD couplings with corrosion resistant steel (CRES) sleeves that would prevent excessive wear of the locking teeth on the light alloy sleeve.  In response to more reported cases of loosened QD couplings resulting in brake problems, further improved QD couplings were introduced in 2001 through SBF100-32-127.  These couplings increase the reliability of the brake system.

             Recently, a brake fire was reported which was caused by a ruptured brake piston.  The fire was quickly extinguished but caused damage to the paint and hydraulic/electrical harness and its components.  Detailed investigation showed that a hydraulic lock must have been present close to the affected brake creating enough internal pressure to rupture the piston.  The most probable scenario for the hydraulic lock is a loosened (not necessarily disconnected) brake QD coupling.  Further investigation of the service experience files at Fokker Services showed that more brake fires have occurred on aeroplanes in a pre-mod SBF100-32-127 configuration.

   In order to reduce the probability of a fluid fire as described in CS 25.863, additional action is deemed necessary.  For the reasons described above, this AD requires repetitive inspections of the affected brake QD couplings and replacement of the QD couplings with improved units.  Installation of the improved QD couplings terminates the repetitive inspections requirements.

James Coyne
Delegate of the Civil Aviation Safety Authority

18 August 2009