Date: 201512
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: B757-200
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
Airspace: Class B ZZZ
ATC / advisory: Tower ZZZ
Aircraft component: Flight Dynamics
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness
Anomaly: Aircraft Equipment Problem Critical; Deviation - Altitude Excursion From Assigned Altitude; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Clearance
Detector: Automation Aircraft Other Automation; Automation Aircraft Terrain Warning; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Landed in Emergency Condition; Flight Crew Returned To Departure Airport; General Flight Cancelled / Delayed
Contributing factors: Equipment / Tooling; MEL; Aircraft
Primary problem: Aircraft

Narrative: I was initially the pilot flying as the First Officer on an Operating Experience (OE) trip. We began the takeoff roll from the runway and everything happened as normal.Importantly; the 80 knot call and verification during takeoff was completed as required. Shortly after becoming airborne; we started to receive numerous EICAS messages and erroneous automated voice callouts (if I recall correctly; these callouts were for wind shear and terrain). The Captain was trying to assist me in handling the airplane in regard to airspeed and altitude as we climbed as we lost all flight director guidance. During this time; he assumed control of the airplane after we realized that the air data information being displayed on my flight instruments was displaying incorrect information.As we continued to climb and changed from Tower control to Departure Control; we elected to stay at 5;000 feet and return to [departure airport]; rather than continue the climb and further flight. Air traffic control began to vector us back towards the arrival runway. We performed the QRH procedure for 'Unreliable Airspeed' since we saw that my airspeed indicator displayed roughly 25-30 knots slower than both the Captain's and the standby instruments. It was then also noted that my altimeter displayed roughly 400 feet lower than the other two altimeters.As part of the QRH procedure; the air data switch on my instrument source selector was changed to the alternate and now matched the Captain's information. He continued to fly the airplane and we returned to land [at our departure airport].As the Captain and I discussed and debriefed the event; we cannot come up with a clear answer to what caused the erroneous indications and automated verbal calls. There were several factors that may have induced these; though they are purely speculation.First; we had a maintenance issue with the window heat that was first trouble-shot and subsequently placed on MEL by maintenance.Secondly; though only discovered after parking at the gate after our return; we were informed that the 2L lavatory was leaking a substantial amount of water onto the floor. Whether either of these issues contributed to or caused the air data problems we received; we are not sure as we left to swap into another airplane; handing this airplane off to maintenance for their investigation.Overall; it was an additional learning opportunity utilizing threat and error management principles and non-normal procedures to safely fly the airplane and return to [our departure airport].




Synopsis: Shortly after becoming airborne; numerous EICAS messages and erroneous automated voice callouts were received; (these callouts were for wind shear and terrain). First Officer's altimeter and airspeed indicator indicated different than the Captain's and standby indicators. After switching to alternate source the instruments agreed. Returned to departure airport.