A B757 LOSES A PNEUMATIC ACCESS DOOR IN FLT IN ZTL AIRSPACE.

Narrative

AFTER LNDG IN RDU; FLT ATTENDANTS TOLD US OF A NOISE INFLT ABOUT 10 MINS AFTER TKOF. DOING A WALKAROUND WE DISCOVERED THE EXTERNAL AIR UNIT PANEL MISSING FROM ACFT WITH JUST A HINGE MISSING AND MINOR SKIN DAMAGE NEXT TO IT. WE GOT A CONTRACT MECH. HE SAID SKIN DAMAGE WAS MINIMAL. WE REFERRED TO THE MEL AND WROTE UP IN THE LOGBOOK THE MISSING PANEL. WE ALSO CALLED OUR FLT CTL MAINT SUPVR TO INFORM THEM OF MISSING PANEL. PREVIOUSLY IN ATL; I CONDUCTED A NORMAL WALKAROUND; I DID NOT SEE ANY OPEN LATCHES. IN FACT; I WENT TO ADJUST THE EXTERNAL AIR CONDITIONING WHICH WAS NOT ON CORRECTLY. THIS UNIT IS ABOUT 18 INCHES FROM THE PANEL WHICH CAME OFF. IF THE LATCHES WERE OUT I WOULD HAVE NOTICED. ALSO THE GND PERSONNEL WHO DISCONNECTED THE AIR HOSE WOULD HAVE SEEN IT. ALSO THE 3-4 PERSONNEL WHO PUSHED BACK THE ACFT. MY FEELING IS THAT THE LATCHES APPEARED FLUSH BUT WERE PROBABLY NOT CONNECTED CORRECTLY. WE ESTIMATED THE PANEL CAME OFF 10-15 MINS AFTER TKOF; 15000-20000 FT; 50-100 MI E OF ATL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT THE DOOR TO THE PNEUMATIC CONNECTION FOR STARTING ENGS IS THE ONE THAT DEPARTED THE ACFT. IT IS A DOOR ABOUT 18 INCHES BY 20 INCHES IN DIMENSION. THE HINGES ARE LOCATED ON THE SIDE OF THE DOOR; WHICH WOULD ALLOW THE DOOR TO PRESENT DRAG IF IT SHOULD OPEN; AND THEREFORE; BE BLOWN OFF OF THE ACFT. THIS FO HAS SINCE BEEN VERY MINDFUL OF THE SECURITY OF ALL THE DOORS WITHIN REACH AND NOW INSPECTS THEM CLOSELY. HE RPTS THAT HE FREQUENTLY POUNDS THEM WITH HIS HAND. SOMETIMES THEY OPEN. IF THEY DO; HE HAS NOTICED THAT NOT ALL THE DOORS HAVE ALL THE LATCHES ON THE DOOR THAT THEY WERE INITIALLY DESIGNED TO HAVE. THROUGH HRS OF USE THE HINGES HAVE BECOME FAULTY. RPTR ALSO FEELS CONFIDENT THAT THE LOST DOOR WAS NOT OPEN DURING HIS PREFLT OR HE WOULD HAVE SEEN IT; BECAUSE IT IS SUCH A LARGE DOOR.