Brake Carrier Quick Disconnects
There have been a number of occurrences where flight crews on the CRJ900 have reported that the aeroplane brakes were dragging, leading to a tire burst or no brake action at all on the landing gear. These events reported the following:
3 cases of brake quick disconnect (QD) fittings found loose which caused a landing with a locked / dragging brake. The loose QD allowed hydraulic pressure to be trapped within the brake causing it to remain locked on landing.
1 case where 2 QD fittings were found loose, causing the landing with no braking ability on the same gear.
3 potential cases where the QD fittings were found disconnected on the production line.
Possible root causes:
Cleaning of the brakes could have lead to inadvertent disengagement of the QD locking tang subsequently leading to QD backing off (getting loose).
QD was not connected properly (locking tang not engaged) after a brake carrier change.
In all cases, the inadvertent disengagement of QD’s was considered to be due to human error.
When compared to the CRJ200/700 design, the CRJ705/900/1000 design is more susceptible to an incorrect installation through the inadvertent disengagement of the locking tangs.
The following Bombardier Aircraft Maintenance Manual (AMM) Temporary Revisions (TR) were released May 2011 which have introduced instructions to utilize 2 methods of lock wire on the brake QD for the CRJ705/900/1000. The addition of the lock wire is to prevent the inadvertent unlocking of the QD.
[TR32-0261]TASK 32-43-26-000-801-A02 - Removal of the Brake Unit Assembly (CRJ900)
[TR32-0262]TASK 32-43-26-400-801-A02 - Installation of the Brake Unit Assembly (CRJ900)
[TR32-0263]TASK 32-43-26-000-801-A03 - Removal of the Brake Unit Assembly (CRJ1000)
[TR32-0264]TASK 32-43-26-400-801-A03 - Installation of the Brake Unit Assembly (CRJ1000)
The intention of Bombardier’s AMM TRs is to advise operators of the importance for correct QD nipple o-ring seal installation and to provide the option to lockwire and retain the QD coupler in an engaged locked position.
Transport Canada Civil Aviation (TCCA) would like to bring to the attention of all operators the possible scenario for incorrect QD installation (see previous TCCA Feedback Magazine-Issue 2/2010, Bombardier ISAR 2009-09-3240 and 2011-06-3243) and to incorporate the recently made available AMM TRs for mitigation.
Water-Bomber Rudder Quadrant Incorrect Installation
During a scheduled “B” check, maintenance discovered that the rudder quadrant located in the rear fuselage area was installed in an inverted or upside down position on its adjoining torque-tube tower-shaft. The aircraft maintenance engineer (AME) noticed that the flight control cables were not in line with the quadrant assembly as seen in figure 1.
Through the extended operation of the improperly installed rear rudder quadrant, abnormal abrasion and wear of the cable guides occurred as seen in figure 2.
Also noted and seen in figure 3 was the quadrants misalignment of approximately 6.3 cm (2.5 in) away from the cable guard.
In this condition, the chances of the rudder cable in leaving or “jumping” out of its quadrant cable guides were significantly increased which would have lead to a complete operational loss of the rudder.
The operator reviewed their maintenance records and concluded that the quadrant had been removed from the rudder tower-shaft during the aircrafts last heavy maintenance “C” check, approximately 2 years previous.
All involved in the installation were advised of the error and a shop memo was issued.
Transport Canada Comments:
Maintenance on an aeroplanes flight control system where it has been adjusted or disturbed in any manner requires the performance of an “independent check” and “second signature” separate from the maintenance release.The required inspection item or “RII” of the system, be that a flight control as with this case or an engine control or propeller rigging must be inspected by a person other than the one who performed the work in compliance with CAR 571.10 Maintenance Release.
- Date modified: