What was found
ON DEPARTURE THROUGH 500 FT THERE WAS NO RESPONSE FROM THE PITCH TRIM. THE NOSE CONTINUED TO PITCH UP AND WE ACTIVATED THE SECONDARY TRIM SYSTEM. AT THAT TIME BOTH SYSTEMS FAILED & THE CAS MESSAGE FOR EACH SYSTEM FAILURE ILLUMINATED. DISENGAGED THE THROTTLES AND DECLARED AN EMERGENCY WHILE TRYING TO GET THE AIRPLANE UNDER CONTROL. AS WE WERE RETURNING TO THE AIRPORT THE SECONDARY TRIM STARTED TO WORK AGAIN AND MADE A NORMAL LANDING. R & R PILOT & CO-PILOT YOKE AP DISCONNECT SWITCHES WITH NEW. OPS CHKD GOOD. REF, AMM 22-10-50, 27-40-00, & 27-40-25.