Narrative:

I was acting as pilot in command and pilot flying; operating from the right seat. I had a CFI (not PIC or pilot flying for takeoff) on board who was going to act as a student later in the flight; in preparation for my upcoming CFI checkride. I had just been given clearance to takeoff on runway xl at ZZZ; by tower. I was demonstrating a short/soft field take off procedure. I taxied onto runway and was aimed at the end of the runway to use all available distance; attempted to turn right to line up with the runway center-line and had the right brake depressed all the way possible with no braking action noted on the right side of the aircraft. Aircraft was still aimed at the runway end identifier lights and immediately pulled idle power and tried right rudder/nose gear to attempt to avoid lights. Aircraft turned slightly to right but was unable to stop in time from impacting the propeller with 1 runway end light. Light appeared to be damaged. I immediately informed the tower that the aircraft was disabled on the runway and that the traffic that was on final needed to go-around. I then notified the tower that I was going to shutdown aircraft and manually reposition the aircraft on the runway so that we could taxi off the runway. I was granted permission and then shut down the aircraft and exited the aircraft. Upon exiting the aircraft I reached down and touched the lower brake line and noted brake (pink/red) fluid. My passenger and I repositioned the aircraft and got back in to start up and taxi off the runway. I contacted the tower and gave a report that we had impact with a runway light and that we were under our own power and requested taxi back to the maintenance ramp. We were granted clearance to exit the runway via the first taxi way and were switched over to ground freq. As I switched onto ground; I noted the controllers mentioning that our aircraft had a blown tire. I gave them a report that we were under our own power and that we had a right brake failure; not a flat tire and that we did have impact with a runway end identifier light. I was able to taxi back to the ramp and verified that the right brake was not responding. I pulled onto the ramp and shut down. We inspected the aircraft for damage and noted a nick and slight bent/edge on the propeller. No other damage was seen or noted besides brake fluid on the right main gear; I could not find the origin of the leak by visual inspection. During the preflight walk around; and during the start of the aircraft for the first flight of the day; I noticed no unusual stains or puddles of fluid on the ground around the main gear. Both pilot stations; left seat and right seat tested their brakes and there was no notice of an issue; both sets of brakes left and right side worked. We also had to make multiple right hand turns and the brakes worked correctly. The brakes also worked correctly during run up and thorough about 3-5 minutes of taxi in which the brakes were used multiple times.

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Original NASA ASRS Text

Title: C172 pilot and instructor reported right main brake failure; resulting in loss of control; and prop contact with runway light.

Narrative: I was acting as pilot in command and Pilot Flying; operating from the right seat. I had a CFI (not PIC or Pilot Flying for takeoff) on board who was going to act as a student later in the flight; in preparation for my upcoming CFI Checkride. I had just been given clearance to takeoff on Runway XL at ZZZ; by Tower. I was demonstrating a short/soft field take off procedure. I taxied onto runway and was aimed at the end of the runway to use all available distance; attempted to turn right to line up with the runway center-line and had the right brake depressed all the way possible with no braking action noted on the right side of the aircraft. Aircraft was still aimed at the runway end identifier lights and immediately pulled idle power and tried right rudder/nose gear to attempt to avoid lights. Aircraft turned slightly to right but was unable to stop in time from impacting the propeller with 1 runway end light. Light appeared to be damaged. I immediately informed the tower that the aircraft was disabled on the runway and that the traffic that was on final needed to go-around. I then notified the tower that I was going to shutdown aircraft and manually reposition the aircraft on the runway so that we could taxi off the runway. I was granted permission and then shut down the aircraft and exited the aircraft. Upon exiting the aircraft I reached down and touched the lower brake line and noted brake (Pink/red) fluid. My passenger and I repositioned the aircraft and got back in to start up and taxi off the runway. I contacted the tower and gave a report that we had impact with a runway light and that we were under our own power and requested taxi back to the Maintenance Ramp. We were granted clearance to exit the runway via the first taxi way and were switched over to ground freq. As I switched onto Ground; I noted the controllers mentioning that our aircraft had a blown tire. I gave them a report that we were under our own power and that we had a right brake failure; not a flat tire and that we did have impact with a runway end identifier light. I was able to taxi back to the ramp and verified that the right brake was not responding. I pulled onto the ramp and shut down. We inspected the aircraft for damage and noted a nick and slight bent/edge on the propeller. No other damage was seen or noted besides brake fluid on the right main gear; I could not find the origin of the leak by visual inspection. During the preflight walk around; and during the start of the aircraft for the first flight of the day; I noticed no unusual stains or puddles of fluid on the ground around the main gear. Both pilot stations; left seat and right seat tested their brakes and there was no notice of an issue; both sets of brakes left and right side worked. We also had to make multiple right hand turns and the brakes worked correctly. The brakes also worked correctly during run up and thorough about 3-5 minutes of taxi in which the brakes were used multiple times.

Data retrieved from NASA's ASRS site 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.