FA20 CREW WAS NOTIFIED THAT THEY HAD AN ALTDEV SEVERAL WKS AFTER THE INCIDENT IN ZID CLASS A.

Narrative

THERE WERE LARGE TSTMS JUST W AND N OF ARPT. JUST AFTER TKOF; AT APPROX 500 FT AGL; OUR RADAR STOPPED WORKING. WE ADVISED DAYTON DEP OF OUR PREDICAMENT AND WE SUGGESTED THAT THEY GIVE US VECTORS TO FOLLOW A B-767 THAT DEPARTED JUST BEFORE US. DURING OUR SUBSEQUENT CLB TO FL350; WE ENCOUNTERED VARIOUS LEVELS OF TURB DUE TO CONVECTIVE WX. A FEW WKS LATER; WE RECEIVED A CALL FROM THE FAA THAT WE HAD DSNDED FROM 28600 FT TO 28200 FT WHILE CLBING TO FL350. THE INDY CTLR HAD NOT MENTIONED ANYTHING TO US DURING THE FLT; BUT APPARENTLY THERE WAS A LOSS OF SEPARATION. CONTRIBUTING FACTORS MAY INCLUDE: 1) POOR ACFT PERFORMANCE DUE TO ANTI-ICE CLB CONFIGN; DENSITY ALT; ETC; 2) TURB WX/FLT CONDITIONS DUE TO TSTM; 3) LOSS OF WX RADAR; 4) PLT FATIGUE (NIGHT FLYING); 5) ATC NOT PASSING ALONG INFO THAT OUR RADAR WAS OTS TO THE NEXT CTLR; 6) COMPLACENCY -- PLTS NOT ADVISING ATC OF ALTDEV (HOWEVER NEITHER THE FO OR MYSELF REMEMBER LOSING THIS MUCH ALT); AND 7) AGING ACFT (FALCON 20) WITH TIRED ENGS. WE SENT A STATEMENT TO THE FAA REGARDING THE EVENT THAT NIGHT; HOWEVER; WE ONLY RECALL BITS AND PIECES SINCE WE WERE NOT IMMEDIATELY TOLD OF THIS ALT INCIDENT. WE LEARNED OF THIS WKS LATER.