Date: 201705
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: DA20-C1 Eclipse
Operator: Personal
Operating under: Part 91
Flight plan: None
Mission: Training
Flight phase: Landing
ATC / advisory: Tower ZZZ
Aircraft component: Normal Brake System
Component problem: Failed
Reporter organization: Personal
Reporter function: Instructor
Reporter qualification: Flight Crew Instrument; Flight Crew Flight Instructor; Flight Crew Commercial; Flight Crew Multiengine
Human factors: Situational Awareness
Anomaly: Aircraft Equipment Problem Less Severe; Ground Event / Encounter Loss Of Aircraft Control; Ground Event / Encounter Object; Ground Excursion Taxiway
Detector: Person Flight Crew
When detected: Taxi
Result: Air Traffic Control Issued New Clearance; Aircraft Aircraft Damaged; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Took Evasive Action
Contributing factors: Airport; Aircraft
Primary problem: Aircraft

Narrative: Myself and [my student] were on a dual flight. The flight started by [the student] conducting the first preflight and shortly after we conducted another preflight together for the Diamond DA-20. We did not find anything wrong or abnormal with the aircraft on either of the inspections. After receiving our taxi clearance we tested the brakes which neither one of us had any problems with. We taxied to the run-up area without any problems including braking; then to [the] runway for departure. We headed north bound for maneuvers (slow flight; power on/off stalls; steep turns and unusual attitudes) and slowly made our way northeast of the airport. We called ZZZ tower requesting to land approximately 1 hour into our flight. [The student] lined up for a straight in approach for [the] runway as told by tower. After flying a stabilized approach we touched down approximately 1;500 feet down [the] runway. He told me that the brakes were not working after touchdown. I took the controls to figure out what was wrong and maintain control. After pressing both brakes I noticed that my right foot was all the way to the floor with no braking power at all. We probably rolled another 500 feet or so which left approximately 4;000 feet remaining. I stated to tower that we will need to make a 180 on the runway due to losing our right brake. Tower specially said 180 as needed and alpha 3 or bravo 3 or whichever we'd like. I initially requested alpha 3. The aircraft starting to turn left towards the grass on the south side of [the] runway. I used the left brake to make 3 180 degree turns to regain control of the aircraft. After preforming that I was able to taxi in a straight line eastbound on [the] runway. A few seconds [later] I realized that taxiway would require a right turn which we would have been unable to do. I was able to make the left hand turn onto bravo 3 and taxi in a straight line until nearing the intersection of bravo 3 and alpha. The aircraft then started turning left. I knew I wouldn't be able to regain control in the little space that was available so I reached to cut the mixture. Putting the mixture control to idle cutoff did not stop the propeller in time from hitting the cover of a taxiway light. I then informed tower that we ended up in the grass and would need assistance. I maneuvered the aircraft in the safest way possible that I deemed necessary at the time.




Synopsis: DA-20 Instructor pilot reported that the brakes failed on one side causing the aircraft to veer off the runway striking a taxiway light cover.