Tecnam P2012 Traveller
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Situational Awareness
Aircraft Equipment Problem Critical; Deviation - Speed All Types; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Loss Of Aircraft Control
Air Traffic Control Provided Assistance; Flight Crew Returned To Departure Airport; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Became Reoriented; Flight Crew Overcame Equipment Problem; General Maintenance Action
Aircraft; Human Factors; Procedure
Takeoff was normal until rotation. Rotated at 75 knots; but didn't lift off until 100 knots. Verified flaps were at takeoff. Climb-out was at 100 knots. At around 400 feet AGL; started a turn and was scanning the instruments when the stall warning went off. The airspeed had dropped to 77 knots. almost instantly. I performed a stall recovery and proceeded to climb to 3;000 feet MSL. At cruise; I noticed all 3 airspeed indicators were showing different airspeeds and the altimeters were different as well. The true airspeed and ground speed were displaying higher than indicated. I pulled the ALT static air and pilot airspeed dropped about 15 knots; but I could not tell which reading was correct. I informed ZZZ Departure and returned for a visual landing. I verified my altitude with ATC and the pilot altitude was correct but the PFD2 was showing about 200 feet lower. On approach airspeed was showing 120 - 130 knots; but the pitch attitude was too high and the controls were mushy. Post-flight walkaround found pitot and static openings OK; but the static system drain lock open.
P2012 Traveller Captain reported performing an air turnback due to unreliable airspeed and altimeter functions caused by the open static system drain.