SR20
Flight Crew Commercial; Flight Crew Private; Flight Crew Instrument
Troubleshooting
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Took Evasive Action
Aircraft
After being cleared onto 27C for take off the student went full power and began his takeoff roll. All engine indications were good and the airspeed indicator was 'alive'. When reaching 70 kts the student attempted to rotate but there was not enough lift so the stall warning horn went off and the aircraft was slightly airborne(>20 feet) then landed back on the runway. By this point enough airspeed had been built up and the student rotated successfully. All of this occurred in the span of about 5 seconds. I took controls and made the decision to continue climbing as there was not enough runway to land. At this point it was clear the airspeed indicator and stand by were wrong so I tried to keep the ASI higher than normal and use known power settings and the feel of the controls to return and land. We landed on 27L without requesting priority handling. Aircraft X had been written up for the ASI on two separate occasions and my student and I briefed that prior to the flight which allowed us to quickly diagnose the problem quickly; however we did not notice anything unusual prior to the takeoff.
Flight Instructor reported an airspeed indicator malfunction that resulted in a return to the departure airport.