2010-12 · NASA ASRS report 923744
A corporate pilot reports having steering and braking controllability problems with his Cessna C421 aircraft during taxi out that contributed to a runway incursion in 15 degree Fahrenheit temperature. In a warm hangar; Maintenance noticed a 2.5 to 3 inch long stick of milky; white ice squirt out of the left flexible brake line near the brake caliper.
At approximately XA:40am local time December 2010; while taxiing and preparing to hold short of Runway 34 at ZZZ; the Pilot became aware of an unusual response to the steering and braking inputs to the aircraft. The Pilot was able to stop the aircraft; but not before the nose of the airplane had crossed the Hold-Short Line at the approach end of Runway 34. The airplane came to a stop directly over the Hold-Short Line; with the nose on the runway side of the line and the tail on the taxiway side of the line. The Pilot immediately notified the ATC Ground Controller of the situation. The Controller then assisted in arranging for an aircraft tow vehicle to push the airplane back behind the Hold-Short Line for Runway 34. This occurred without incident. After completing the Pre-takeoff Checks; the Pilot noticed that the aircraft still would not taxi or brake properly. The Pilot then asked for and received an ATC clearance to taxi back to the local Fixed Based Operator (FBO) for an Inspection into the cause of the problem. This was accomplished without further incident. Maintenance subsequently found that because of the very cold temperatures that morning; an amount of condensation moisture had frozen in the lower brake lines; thereby preventing the brakes from operating properly and preventing the airplane from being stopped on schedule; before reaching the previously mentioned runway Hold-Short Line.The problem was corrected; and the aircraft then operated normally and without incident.
Reporter stated they were only on the ground in ZZZ for about an hour and a half with temperature approximately 15-18 degrees F (Fahrenheit); before attempting to fly back out with passengers. When they realized they were having steering and braking problems they decided to taxi back to the FBO hangar. Even then; they had to use high power to get to the hangar. Reporter stated that even after the C421 was in the heated hangar for at least an hour; Maintenance was still having trouble getting the disc brakes to release. Mechanics disconnected the flexible brake lines at the left and right brake calipers. There are hard brake lines up in the wing area; but the flex lines run down the Gear to the brake calipers. While pressing on the brake pedals numerous times; suddenly a 2.5' to 3' inch long piece of white; milky looking ice squirted out of the flexible brake line. The ice was the same diameter as the brake line. In his forty years of flying in cold climates; he has never seen that amount of moisture come out of a brake line. Only the left brake seemed to have that amount of moisture accumulation. Reporter stated after they left ZZZ and flew home; their Maintenance facility removed and replaced all the brake fluid in the Brake System. Maintenance performs an Annual Inspection every twelve months on their C421's; but the brake fluid is not changed. In fact; Cessna's Service Manual Inspection Time limits for the Brake System plumbing only requires an Inspection of the brake lines for leaks; condition and security of the brake line routing and support clamps and to service the Brake Master Cylinder.Reporter stated that on the same morning when they had to return to the FBO hangar in ZZZ for their brake issue; Mechanics told them another Cessna C421 aircraft was in earlier for brakes locking-up and fluid freezing in the lines. His Maintenance facility has decided they will replace all the brake fluids in their aircraft once a year during each aircraft's Annual Inspections; even though Cessna does not require or recommend the procedure.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.
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