B737-800
Flight Crew Air Transport Pilot (ATP)
Confusion; Troubleshooting; Human-Machine Interface; Distraction
Aircraft Equipment Problem Critical
Flight Crew Took Evasive Action; Flight Crew Returned To Departure Airport; General Declared Emergency
Aircraft
Climbing out; Captain lost all indications on PFD of altitude; airspeed; vertical speed; and FMA annunciations. Same indications lost in HUD. First Officer lost Flight Director indications.  Autothrottle disengaged; autopilot would not engage. Yaw damper disengaged. No fault alerts or warning lights were given. I transitioned duties of flying to the First Officer and worked the problem.  Uncertain if the issue was an IRS; FCC or something else; I declared an emergency and returned to the airport uneventfully.
The reporter stated that follow up on this event determined that the Number 1 ADIRU failed even though no fault annunciation was displayed. The Captain's PFD has the compass rose with tick markers; the speed and altitude tapes were displayed but no data accompanied the tapes. He did recall that even though the First Officer's Flight Director initially was lost; by the time they began the approach Flight Director information was again available. He said there was great deal of activity during the air turn back and he was basically without information to back up the First Officer during the night VMC return.
After takeoff a B737-800 Captain's PFD and HUD lost altitude; airspeed; vertical speed; FMA annunciations; the autothrottle/autopilot would not engage and the yaw damper disengaged. An emergency was declared and the flight returned to the departure airport.