Narrative:

There was a minor incident involving a caravan and myself due to a complete loss of braking power on taxiway U at addison airport in dallas, tx. I showed up to the airport earlier for a scheduled departure and noticed the aircraft was in the hangar being worked on by maintenance. Maintenance began to put the aircraft back together and towed the plane out of the hangar to conduct run-up checks on the maintenance previously performed. They had a few minor adjustments and released the aircraft to me and asked me to check the battery voltage output on start-up and the suction gauge at 1750 propeller RPM. Another few adjustments were made and first officer and I were released. The flight blocked out and we began to taxi out of the ramp. I tapped the brakes and noticed they were a little bit mushy. I immediately turned and told first officer 'these brakes feel kind of spongy.' first officer didn't think much of it at that moment but unbeknownst to us, brand new brakes had just been put on the aircraft. As I began to taxi out of the ramp and onto taxiway U, I began to conduct the routine taxi checks while steering the aircraft with my feet and pwring in the idle position so as not to taxi fast on the narrow taxiway. As I approached taxiway a, the aircraft got off centerline approximately 10 degrees from taxiway U. I needed to slow down to make a smooth right turn onto taxiway a and simultaneously correct left, back to centerline, so I simply applied a little bit of braking while steering slightly to the left. The left main gear brake did not respond, but the right main gear did, canceling my slight left steering correction from the approximately 10 degree centerline deviation. When I realized that the aircraft was not correcting back to the left, I applied more left brake and a little right brake, but the aircraft began to turn more to the right and further from the centerline. It seemed like both brakes were weak, but the right brake seemed slightly more effective. When the deviation seemed like it was getting out of hand, I applied full left and right braking power and full thrust reverse and told first officer that we had lost the brakes. I put all my body weight on both brakes, but the aircraft kept rolling with a slight right turn. The left brake had zero response and the right brake barely responded. First officer told me, 'I have the plane!' he, too, applied full brakes prior to touching the grass on the right side of the taxiway, but the aircraft simply did not respond effectively to our recovery inputs. As the aircraft's right main gear came off the taxiway and onto the grass, the right main gear brake locked and the plane turned sharply to the right making a 180 degree turn into the grass. As the aircraft came to a complete stop in the grass, I immediately called ground control and told them that we had to stop to check something. Ground control responded by saying, 'let me know when you're ready to taxi to runway 15.' first officer called dispatch and requested maintenance to come and pull us out of the grass with the tug. While both first officer and I waited for the tug, we shut down the aircraft and both agreed that the brakes had failed. When maintenance showed up, they asked us what had happened, and I responded that we had lost braking power. The mechanic told me right then that the aircraft had just had new brakes put on and that there was possibly still air in the hydraulic line. He asked me to pump the brakes. I began to pump the brakes and the pressure began to increase with the pumping. The mechanics towed us out of the grass and onto a wide ramp area where I tested the brakes and things got more ctlable. The mechanic told us to break in the brakes by applying them while we taxi. First officer and I completed the brake check and the brakes were more ctlable, so we continued with our mission and proceeded to taxi without further incident or any damage to property. I believe this situation was caused by maintenance not conducting a post test run of the aircraft brakes and not communicating to me, the pilot, that brakes were recently replaced. This situation can be avoided in the future by communicating as close as possible with mechanics after any and all maintenance inspections.

Google
 

Original NASA ASRS Text

Title: A CARGO PART 135 C208 PIC LOSES CTL OF THE ACFT DURING TAXI AND DEPARTS THE TXWY AT ADS, TX.

Narrative: THERE WAS A MINOR INCIDENT INVOLVING A CARAVAN AND MYSELF DUE TO A COMPLETE LOSS OF BRAKING PWR ON TXWY U AT ADDISON ARPT IN DALLAS, TX. I SHOWED UP TO THE ARPT EARLIER FOR A SCHEDULED DEP AND NOTICED THE ACFT WAS IN THE HANGAR BEING WORKED ON BY MAINT. MAINT BEGAN TO PUT THE ACFT BACK TOGETHER AND TOWED THE PLANE OUT OF THE HANGAR TO CONDUCT RUN-UP CHKS ON THE MAINT PREVIOUSLY PERFORMED. THEY HAD A FEW MINOR ADJUSTMENTS AND RELEASED THE ACFT TO ME AND ASKED ME TO CHK THE BATTERY VOLTAGE OUTPUT ON START-UP AND THE SUCTION GAUGE AT 1750 PROP RPM. ANOTHER FEW ADJUSTMENTS WERE MADE AND FO AND I WERE RELEASED. THE FLT BLOCKED OUT AND WE BEGAN TO TAXI OUT OF THE RAMP. I TAPPED THE BRAKES AND NOTICED THEY WERE A LITTLE BIT MUSHY. I IMMEDIATELY TURNED AND TOLD FO 'THESE BRAKES FEEL KIND OF SPONGY.' FO DIDN'T THINK MUCH OF IT AT THAT MOMENT BUT UNBEKNOWNST TO US, BRAND NEW BRAKES HAD JUST BEEN PUT ON THE ACFT. AS I BEGAN TO TAXI OUT OF THE RAMP AND ONTO TXWY U, I BEGAN TO CONDUCT THE ROUTINE TAXI CHKS WHILE STEERING THE ACFT WITH MY FEET AND PWRING IN THE IDLE POS SO AS NOT TO TAXI FAST ON THE NARROW TXWY. AS I APCHED TXWY A, THE ACFT GOT OFF CTRLINE APPROX 10 DEGS FROM TXWY U. I NEEDED TO SLOW DOWN TO MAKE A SMOOTH R TURN ONTO TXWY A AND SIMULTANEOUSLY CORRECT L, BACK TO CTRLINE, SO I SIMPLY APPLIED A LITTLE BIT OF BRAKING WHILE STEERING SLIGHTLY TO THE L. THE L MAIN GEAR BRAKE DID NOT RESPOND, BUT THE R MAIN GEAR DID, CANCELING MY SLIGHT L STEERING CORRECTION FROM THE APPROX 10 DEG CTRLINE DEV. WHEN I REALIZED THAT THE ACFT WAS NOT CORRECTING BACK TO THE L, I APPLIED MORE L BRAKE AND A LITTLE R BRAKE, BUT THE ACFT BEGAN TO TURN MORE TO THE R AND FURTHER FROM THE CTRLINE. IT SEEMED LIKE BOTH BRAKES WERE WEAK, BUT THE R BRAKE SEEMED SLIGHTLY MORE EFFECTIVE. WHEN THE DEV SEEMED LIKE IT WAS GETTING OUT OF HAND, I APPLIED FULL L AND R BRAKING PWR AND FULL THRUST REVERSE AND TOLD FO THAT WE HAD LOST THE BRAKES. I PUT ALL MY BODY WT ON BOTH BRAKES, BUT THE ACFT KEPT ROLLING WITH A SLIGHT R TURN. THE L BRAKE HAD ZERO RESPONSE AND THE R BRAKE BARELY RESPONDED. FO TOLD ME, 'I HAVE THE PLANE!' HE, TOO, APPLIED FULL BRAKES PRIOR TO TOUCHING THE GRASS ON THE R SIDE OF THE TXWY, BUT THE ACFT SIMPLY DID NOT RESPOND EFFECTIVELY TO OUR RECOVERY INPUTS. AS THE ACFT'S R MAIN GEAR CAME OFF THE TXWY AND ONTO THE GRASS, THE R MAIN GEAR BRAKE LOCKED AND THE PLANE TURNED SHARPLY TO THE R MAKING A 180 DEG TURN INTO THE GRASS. AS THE ACFT CAME TO A COMPLETE STOP IN THE GRASS, I IMMEDIATELY CALLED GND CTL AND TOLD THEM THAT WE HAD TO STOP TO CHK SOMETHING. GND CTL RESPONDED BY SAYING, 'LET ME KNOW WHEN YOU'RE READY TO TAXI TO RWY 15.' FO CALLED DISPATCH AND REQUESTED MAINT TO COME AND PULL US OUT OF THE GRASS WITH THE TUG. WHILE BOTH FO AND I WAITED FOR THE TUG, WE SHUT DOWN THE ACFT AND BOTH AGREED THAT THE BRAKES HAD FAILED. WHEN MAINT SHOWED UP, THEY ASKED US WHAT HAD HAPPENED, AND I RESPONDED THAT WE HAD LOST BRAKING PWR. THE MECH TOLD ME RIGHT THEN THAT THE ACFT HAD JUST HAD NEW BRAKES PUT ON AND THAT THERE WAS POSSIBLY STILL AIR IN THE HYD LINE. HE ASKED ME TO PUMP THE BRAKES. I BEGAN TO PUMP THE BRAKES AND THE PRESSURE BEGAN TO INCREASE WITH THE PUMPING. THE MECHS TOWED US OUT OF THE GRASS AND ONTO A WIDE RAMP AREA WHERE I TESTED THE BRAKES AND THINGS GOT MORE CTLABLE. THE MECH TOLD US TO BREAK IN THE BRAKES BY APPLYING THEM WHILE WE TAXI. FO AND I COMPLETED THE BRAKE CHK AND THE BRAKES WERE MORE CTLABLE, SO WE CONTINUED WITH OUR MISSION AND PROCEEDED TO TAXI WITHOUT FURTHER INCIDENT OR ANY DAMAGE TO PROPERTY. I BELIEVE THIS SIT WAS CAUSED BY MAINT NOT CONDUCTING A POST TEST RUN OF THE ACFT BRAKES AND NOT COMMUNICATING TO ME, THE PLT, THAT BRAKES WERE RECENTLY REPLACED. THIS SIT CAN BE AVOIDED IN THE FUTURE BY COMMUNICATING AS CLOSE AS POSSIBLE WITH MECHS AFTER ANY AND ALL MAINT INSPECTIONS.

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.