J3 CUB WITH INSTRUCTOR AND STUDENT ABOARD VEERS OFF THE RWY AFTER LANDING WHEN LEFT BRAKE FAILS.

Narrative

I WAS WITH A STUDENT IN A J3 CUB DOING A SESSION OF PRACTICE TKOFS AND LNDGS IN THE PATTERN AT ZZZ. THE STUDENT WAS IN THE REAR SEAT; AND I WAS IN THE FRONT. THE WIND WAS VARIABLE AT 4 KTS; MOSTLY OUT OF THE N. WE WERE USING RWY XX IN CONTACT WITH THE TWR DURING THE WHOLE SESSION. ON OUR FINAL LNDG; TOUCHDOWN WAS SMOOTH AND ALL WHEELS WERE FIRMLY ON THE GND AS EVEN BRAKING WAS APPLIED. THE L BRAKE INSTANTLY AND COMPLETELY FAILED. THE ACFT SWERVED SHARPLY TO THE R; INTO THE GRASS ALONGSIDE THE RWY. I STRUGGLED FOR DIRECTIONAL CTL TO BRING THE ACFT BACK TOWARDS THE RWY; BUT APPARENTLY THE STUDENT HAD FROZEN AT THE CTLS AND THE ACFT WAS NOT RESPONDING AS EXPECTED. AS I STRUGGLED; I MANAGED TO AVOID THE BIG RWY SIGN; BUT WE KNOCKED DOWN A SMALL TXWY SIGN; AND CONTINUED TO VEER R TOWARD A LARGE SECTION OF ROW HANGARS. RAPID ADJUSTMENTS IN PWR SETTING AND CTL FORCES ENABLED ME TO STOP THE ACFT ON THE PAVED TXWY A SHORT DISTANCE FROM THE HANGARS. WE SHUT THE ACFT DOWN; NOTIFIED THE TWR; AND PUSHED THE ACFT OUT OF THE WAY; BTWN ROWS OF HANGARS. WE SURVEYED THE DAMAGE WHILE A TUG WAS DISPATCHED TO RETRIEVE THE ACFT. THE L WHEEL WAS COMPLETELY SOAKED WITH HYD FLUID; THE L X-BRACE ON THE MAIN WAS DINGED UP; AND THE PROP TIPS WERE BENT SLIGHTLY AND HAD PAINT ON THEM FROM STRIKING THE TXWY SIGN. THE PLTS SUFFERED NO HARM OR INJURY. THE CAUSAL FACTORS WERE MECHANICAL FAILURE OF THE BRAKE; EXACERBATED BY THE INAPPROPRIATE ACTIONS OF THE STUDENT ON THE CTLS. UPON REVIEW OF THE INCIDENT; THE BRAKE FAILURE WAS NOT CATASTROPHIC IN ITSELF. THE PROB COULD HAVE BEEN MANAGED WITH MINIMAL DAMAGE AS THE CUB IS SUCH A LIGHT AND MANEUVERABLE ACFT. THE GREATER FACTOR WAS THE PLT EXPERIENCE AND TRAINING; WITH AN APPROPRIATE AND RAPID RESPONSE TO SUCH AN EVENT. IT IS A SHARP REMINDER THAT OUR CURRENT TRAINING ENVIRONMENT IS VERY FOCUSED ON EQUIP INSIDE THE COCKPIT; AND NOT ENOUGH TIME IS BEING SPENT ON TRULY KNOWING AND FLYING THE ACFT. GLASS PANELS ARE AMAZING TOOLS; BUT CAN THE PLT HANDLE A MECHANICAL FAILURE IN THE AIRPLANE? PLT TRAINING MUST ENSURE THEY CAN NOW AND IN THE FUTURE.