B717 (Formerly MD-95)
Flight Crew Air Transport Pilot (ATP)
Troubleshooting; Human-Machine Interface; Confusion
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Weight And Balance
Flight Crew FLC Overrode Automation; Flight Crew Landed in Emergency Condition; Flight Crew Returned To Departure Airport; General Declared Emergency
Aircraft; Human Factors
After takeoff with PROF and NAV armed; the 'magenta line' disappeared. At approximately 3;000 MSL; the throttles reduced to idle and were initially unresponsive. After selecting 'prof' again; the autothrottles returned. Both FMS's were totally unresponsive and we were not able to navigate to ANY fix. We then decided to return to our departure airport and also realized we were overweight by 6;000 pounds. We then declared an emergency and landed uneventfully. We were not able to change the destination nor were we able to hard tune the ILS frequency for the approach.
When both FMCs ceased to function shortly after takeoff the flight crew of a B-717 opted to declare an emergency and return to their departure airport. They landed safely; 6;000 pounds overweight.