ALTDEV ALT OVERSHOT IN CLB.

Narrative

WE WERE CLBING TO FL290 AND USING OMEGA TO GO DIRECT TO LGC VOR. JUST AS THE AUTOPLT WAS CAPTURING FL290; ZTL CALLED TO GIVE US DIRECT TO TIROE AND DSCNT PLT DISCRETION TO FL240. TIROE IS A FIX ON THE LA GRANGE ARR INTO ATLANTA. WE HAD NOT PUT TIROE INTO THE OMEGA; SO THE FO OFFERED TO READ THE COORDINATES TO ME SINCE THE OMEGA IS ON MY SIDE OF THE CONSOLE. I AGREED AND WHEN I FINISHED ENTERING THE COORDINATES I GAVE THE OMEGA A DIRECT TRACK TO TIROE. JUST AS I FINISHED; I GLANCED AT THE ALT AND REALIZED THAT THE AUTOPLT HAD NOT LEVELED AT FL290. WE WERE PASSING THROUGH FL296. I DISENGAGED THE AUTOPLT AND CORRECTED BACK TO FL290. SINCE WE HAD BEEN CLRED PLT DISCRETION TO FL240; I DECIDED TO GO AHEAD AND DSND TO FL240 AT THIS TIME. THE REASON THAT THE AUTOPLT HAD NOT COMPLETED ITS LEVELOFF AT FL290 WAS THAT THE FO; WITHOUT ME NOTICING; HAD DIALED IN FL240 BEFORE THE AUTOPLT HAD COMPLETED ITS LEVELOFF. IF YOU CHANGE THE ALT IN THE ALT ALERT ON THIS ACFT BEFORE IT HAS COMPLETED ITS LEVELOFF; IT WILL CONTINUE TO CLB OR DSND AT ITS PRESENT RATE. IT ALSO DID NOT GIVE US AN ALT ALERT WARNING BECAUSE WE WERE STILL CLBING AND THE NEW ALT THAT WAS SET IN WAS MORE THAN 1000 FT BELOW OUR CURRENT ALT. THIS WAS A CASE OF NOT FIRST FLYING THE AIRPLANE. I SHOULD NOT HAVE LET THE NAV TAKE PRIORITY OVER THE FLYING OF THE AIRPLANE. IF I HAD MADE THE FO PUT IN THE COORDINATES FOR TIROE BY HIMSELF; I WOULD HAVE BEEN ABLE TO MAKE SURE THAT THE AIRPLANE LEVELED OFF AT THE ASSIGNED ALT. I WOULD PROBABLY ALSO NOTICED THAT THE ALT IN THE ALT ALERT WINDOW HAD BEEN CHANGED EVEN BEFORE IT PASSED THROUGH FL290. SUPPLEMENTAL INFO FROM ACN 300066: THE CAPT ASKED FOR MY HELP IN REPROGRAMMING THE OMEGA TO THE NEW FIX WHICH WAS NOT PROGRAMMED ON OUR FLT PLAN. RECOMMENDATIONS: 1) ATC: DO NOT GIVE A DSCNT PRIOR TO LEVEL OFF AT CRUISE ALT AND ALSO REALIZE THAT THE DIRECT NAV CAPABILITY OF THE B-727 WITH OMEGA IS MORE COMPLEX THAN THE MORE MODERN 'GLASS COCKPIT;' FMS EQUIPPED ACFT. 2) CREWS: FINISH 1 PHASE OF FLT INCLUDING LEVEL OFF PRIOR TO BEGINNING THE NEXT. WHEN CLRED TO A SPOT NOT PROGRAMMED; HAVE THE PNF DO ALL THE ADDITIONAL PROGRAMMING WHILE THE PF CONCENTRATES ON FLYING. ASK FOR A VECTOR IN ORDER TO COMPLY WITH THE CLRNC UNTIL THE NAV COMPUTER CAN BE SUCCESSFULLY REPROGRAMMED AND CHKED FOR ACCURACY. FLY THE AIRPLANE FIRST!