Date: 202006
Location: ZZZ.Airport, US
Flight conditions: Mixed
Light: Daylight
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch
Aircraft component: Air Data Computer
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; First Officer
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown
Anomaly: Aircraft Equipment Problem Critical; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Landed in Emergency Condition; Flight Crew Returned To Departure Airport; Flight Crew FLC Overrode Automation; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft; Procedure; Human Factors
Primary problem: Aircraft

Narrative: Just before calling 100 KTS (around 98) I heard an A/T 'snapping' off followed by red flashing A/T (auto-throttle) light which I canceled. Looked up at my airspeed indicator saw 105 and accelerating (100 KTS called as 105). Looked at CA (Captain's) airspeed indicator and saw it around 68 and hovering. (Not sure if he cross checked his IAS but no acknowledgment was received). Glanced at STBY indicator and saw IAS around 113 and accelerating. Announced AIS Disagree flag to the CA and said I have 'good data on my side - I can take the airplane. Transfer of control was performed. Rotation was performed few knots fast. Airborne at safe altitude CA initiated the EEC (Electronic Engine Control) Alternate Mode of Checklist for some reason (EEC's had switched to alt - same had happened in ZZZ1 after the 2nd engine start and was cleared with Maintenance) although I stated we have an Unreliable Airspeed with IAS Disagree flags. -*50 % of the time Unreliable Altitude flags on the altimeter were displayed also - CA never acknowledged seeing the ALT Disagree flag*- CA wanted to climb to 16;000 feet; which I questioned. (I believe I said 'you are not really thinking about continuing all the way to ZZZ2 with this so why climb higher than needed' and he responded that he wants to get out of the bumps (moderate to severe turbulence was reported in the area due to thunderstorms - we had light turbulence for most of the climbout). We flew in MVFR to VFR mostly. I believe we leveled off at 12;000 feet and then CA notified ATC. EEC checklist was performed but I don't recall CDS (Common Display System) displaying DSPLY SOURCE. I reminded him to pull out the QRC Unreliable Airspeed checklist which was pulled out although FD (Flight Director) switches were omitted by the CA and never turned off (I should have verified this memory item) The CA never read the QRH for the Unreliable Airspeed checklist; but the person on the jumpseat did (not sure if he was delegated for the QRH reading by the CA); omitting the conditions for the checklist and some other items but catching the FD switches verifying the pitch and power settings from the QRH for '800 series. Normal arrival with delayed vectors and landing performed. The flight never exceeded any flight parameters and limitations and stayed in normal flight envelope at all times. During the flight CA airspeed varied from 330 plus activating the high speed clacker to as low as 46 activating the stall shaker making the communication at times difficult. The light turbulence associated with thunderstorms created another distraction.




Synopsis: B737-800 First Officer reported confusion between flight crew after auto-throttle fail on takeoff was followed by air data computer failure causing unreliable airspeed; resulting in an Air Turn Back and Landing