C172 instructor pilot reported loss of directional control on landing roll related to brake failure.

Attributes
ACN	1372654
Time
Date	201607
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Flight Phase	Landing
Flight Plan	VFR
Component
Aircraft Component	Brake System
Person 1
Function	Instructor Pilot Not Flying
Qualification	Flight Crew Commercial Flight Crew Flight Instructor Flight Crew Instrument
Experience	Flight Crew Last 90 Days 85 Flight Crew Total 445 Flight Crew Type 445
Events
Anomaly	Aircraft Equipment Problem Less Severe Ground Event / Encounter Loss Of Aircraft Control Ground Excursion Runway

Narrative:

During a lesson with a student; the aircraft lost right side brakes and ran off the runway. It was a full stop landing. The landing was made safely; flaps were retracted and then brakes were applied to slow the aircraft. The airplane began moving toward the left and my student said she could not control the aircraft to the right. As the instructor; I began pushing on the right side and within an instant the aircraft turned sharp left off the runway and into the grass. The rudder and brake pedals had zero control under the right foot for either left or right side pilot. Once the airplane came to stop in the grass beside the runway; I was able to add power and continue a left turn and taxi the aircraft across the runway and onto the taxiway. Once cleared to cross [the runway] I began to taxi the airplane but once across the runway I began to slow the aircraft and once again the airplane had no control on right side rudder or brakes and again turned sharp left into the ditch. At this point our company maintenance was called to tow the aircraft back to maintenance.

Original NASA ASRS Text

Title: C172 instructor pilot reported loss of directional control on landing roll related to brake failure.

Narrative: During a lesson with a student; the aircraft lost right side brakes and ran off the runway. It was a full stop landing. The landing was made safely; flaps were retracted and then brakes were applied to slow the aircraft. The airplane began moving toward the left and my student said she could not control the aircraft to the right. As the instructor; I began pushing on the right side and within an instant the aircraft turned sharp left off the runway and into the grass. The rudder and brake pedals had zero control under the right foot for either left or right side pilot. Once the airplane came to stop in the grass beside the runway; I was able to add power and continue a left turn and taxi the aircraft across the runway and onto the taxiway. Once cleared to cross [the runway] I began to taxi the airplane but once across the runway I began to slow the aircraft and once again the airplane had no control on right side rudder or brakes and again turned sharp left into the ditch. At this point our company maintenance was called to tow the aircraft back to maintenance.

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.