Narrative:

While taxiing for takeoff at pym, I applied the brakes and noticed the nose was pulling to the right. As I approached the turn from the taxiway to the runway, there was an airplane on the right in the run-up area so I decided to use minimum braking to prevent my airplane from turning into the direction of the parked airplane. I planned to stop just after passing the parked airplane but the poor braking action caused me to roll just past the edge of the hard surface, onto the hard-packed dirt. I thought the problem was due to brake fade due to the fact that there was a tailwind on the taxiway and even with the engines at idle, I had to ride the brakes to taxi slowly. When I stopped, I seemed to have plenty of brake pedal pressure, so I taxied back onto the hard surface with no problem, and was able to stop satisfactorily. Since the brakes seemed to be working ok, I thought they had cooled off and would be no more problem. I departed and planned to have the brake system checked when I returned home. When I arrived at my destination, I noticed the left brake was ineffective on rollout and checked the wheel assembly after parking the aircraft. The problem, I discovered, was due to the separation of the brake disk from the wheel assembly. The disk section was held in place by the brake caliper assembly which is why I still had good pedal pressure. The aircraft was grounded for repairs. Judgemental factors: I should not have assumed the problem was due to overheating, etc. The aircraft should have been inspected before departing the airport. Even though I had braking (apparently from the right only), I should have made sure the aircraft was airworthy before flight. Fortunately, no one was injured. The next time I have a problem, I will get it checked out rather than making unfounded assumptions.

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Original NASA ASRS Text

Title: TXWY EXCURSION AFTER BRAKE FAILURE EVIDENT. PLT ELECTS TO DEP ARPT WITH ACFT AS IS.

Narrative: WHILE TAXIING FOR TKOF AT PYM, I APPLIED THE BRAKES AND NOTICED THE NOSE WAS PULLING TO THE R. AS I APCHED THE TURN FROM THE TXWY TO THE RWY, THERE WAS AN AIRPLANE ON THE R IN THE RUN-UP AREA SO I DECIDED TO USE MINIMUM BRAKING TO PREVENT MY AIRPLANE FROM TURNING INTO THE DIRECTION OF THE PARKED AIRPLANE. I PLANNED TO STOP JUST AFTER PASSING THE PARKED AIRPLANE BUT THE POOR BRAKING ACTION CAUSED ME TO ROLL JUST PAST THE EDGE OF THE HARD SURFACE, ONTO THE HARD-PACKED DIRT. I THOUGHT THE PROB WAS DUE TO BRAKE FADE DUE TO THE FACT THAT THERE WAS A TAILWIND ON THE TXWY AND EVEN WITH THE ENGS AT IDLE, I HAD TO RIDE THE BRAKES TO TAXI SLOWLY. WHEN I STOPPED, I SEEMED TO HAVE PLENTY OF BRAKE PEDAL PRESSURE, SO I TAXIED BACK ONTO THE HARD SURFACE WITH NO PROB, AND WAS ABLE TO STOP SATISFACTORILY. SINCE THE BRAKES SEEMED TO BE WORKING OK, I THOUGHT THEY HAD COOLED OFF AND WOULD BE NO MORE PROB. I DEPARTED AND PLANNED TO HAVE THE BRAKE SYS CHKED WHEN I RETURNED HOME. WHEN I ARRIVED AT MY DEST, I NOTICED THE L BRAKE WAS INEFFECTIVE ON ROLLOUT AND CHKED THE WHEEL ASSEMBLY AFTER PARKING THE ACFT. THE PROB, I DISCOVERED, WAS DUE TO THE SEPARATION OF THE BRAKE DISK FROM THE WHEEL ASSEMBLY. THE DISK SECTION WAS HELD IN PLACE BY THE BRAKE CALIPER ASSEMBLY WHICH IS WHY I STILL HAD GOOD PEDAL PRESSURE. THE ACFT WAS GNDED FOR REPAIRS. JUDGEMENTAL FACTORS: I SHOULD NOT HAVE ASSUMED THE PROB WAS DUE TO OVERHEATING, ETC. THE ACFT SHOULD HAVE BEEN INSPECTED BEFORE DEPARTING THE ARPT. EVEN THOUGH I HAD BRAKING (APPARENTLY FROM THE R ONLY), I SHOULD HAVE MADE SURE THE ACFT WAS AIRWORTHY BEFORE FLT. FORTUNATELY, NO ONE WAS INJURED. THE NEXT TIME I HAVE A PROB, I WILL GET IT CHKED OUT RATHER THAN MAKING UNFOUNDED ASSUMPTIONS.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.