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pdf Gfa 168an Popular

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Gfa 168an

SERIOUS DETERIORATION OF AIRBRAKE ARM BALL BEARINGS DUE TO WATER INGRESS AS A RESULT OF WATER COLLECTING IN THE DIVE BRAKE BOX  

Applicable to the DG 500 series gliders however other DG gliders may exhibit the same problem. DG 500 glider VH-VMF serial number 5E251X80 was exhibiting increasing freeplay in the chordwise direction at the inner airbrake arms where the swinging arm attaches to the airbrake paddle. The problem was evident on both wings; freeplay with the airbrakes fully extended was of the order of 3 to 4 millimeters. The problem had become steadily worse over the period of a year. Removal of the swinging arm assembly revealed the problem as shown in the attached photograph. There was severe corrosion in the pivot arm ball bearings due to water ingress past the plastic face seal to the point where in places the bearing cage was nonexistent. The inner surface of the tubes which form the tunnels into which the bearings are pressed also showed corrosion. On one occasion this DG500 had spent one week parked outside with the airbrake boxes collecting and holding rain water.