Other / Unknown
Aircraft Equipment Problem Critical
General Declared Emergency
Aircraft
I was pilot flying with autopilot OFF departing ZZZ for SJC. At 'about' 3;000 FT in the westbound turn on the RNAV departure both digital flight guidance computers (DFGC) kicked off leaving me with blank FMA; no autothrottle or autopilot if I wanted it; no CDI; no altitude pre-select/alerted and a few other items. I said I was unable RNAV departure and need a heading. After a bit of trouble shooting with no luck; we were unable to restore the DFGC's it was decided to return to departure airport. An emergency was declared and we received heading and altitudes back to ZZZ in VMC. After a smooth landing we taxied back to the gate and switched airplanes.
Rather than try to fly with the conditions for more than 2 hours to use up enough fuel to be under max landing weight; I decided to declare an emergency; and return immediately to ZZZ and land overweight. We were vectored by ATC back to ZZZ for a visual approach. We made a normal approach to a very soft touchdown; slowed using normal braking procedures; exited the runway and taxied to the gate without incident. Maintenance then came aboard and found what they said were multiple failures in the maintenance check functions and took the plane out of service.
Air Carrier on initial climb experienced a digital flight guidance failure on both systems resulting in a return to the departure airport.