A LEARJET 35 DSNDING THROUGH FL250 EXPERIENCED A LOUD BANG WITH DECELERATION AND SLIGHT BRIEF PITCH NOSE DOWN. R ENG UPPER COWLING DEPARTED ACFT.

Narrative

I WAS PF ON JUL/TUE/03 DIRECT TO ZZZ DSNDING OUT OF FL250 AND EXPERIENCED A LOUD BANG ASSOCIATED WITH A DECELERATION AND A NOSE DOWN PITCHING FOR A BRIEF SECOND. AFTER THE OCCURRENCE; I SPOKE WITH THE CAPT I WAS FLYING WITH AND WE WENT OVER ALL SYS TO EVALUATE WHAT HAD HAPPENED. I SLOWED DOWN TO 250 KIAS AND ALL ENG/HYD/ELECTRICAL INSTS WERE ALL NORMAL. ALSO; ALL FLT CTLS WERE OPERATING NORMALLY. AFTER LNDG AND REQUESTING EMER SVCS THE FIRE TRUCK TOLD US THAT OUR R ENG COVER WAS MISSING; SO WE SHUT DOWN THAT ENG AND TAXIED TO MAINT. NOBODY WAS INJURED TO OUR KNOWLEDGE. NO FLT CTL LOSS OCCURRED. A PROPER PREFLT ACTION WAS CONDUCTED BY MYSELF THAT MORNING AND ALL APPEARED NORMAL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED HE WAS FLYING THE ACFT AND DSNDING FROM FL260 TO FL250 WHEN A YAW TO THE R WAS FELT WITH SLIGHT NOSE DOWN PITCH. THE RPTR SAID THE AIRPLANE WAS SLOWED TO 250 KTS AND ALL ENG; HYD AND ELECTRICAL INSTS WERE CHKED AND FOUND NORMAL. THE RPTR STATED THAT ON THE GND IT WAS DISCOVERED THE R ENG UPPER COWLING HAD DEPARTED THE ACFT AND THE R LOWER COWLING WAS FOLDED INBOARD AGAINST THE AFT FUSELAGE. THE RPTR SAID WHEN THE UPPER COWLING LEFT THE AIRPLANE IT STRUCK THE DORSAL FIN DAMAGING THE VHF ANTENNA. IT THEN DAMAGED THE R LOWER ELEVATOR SURFACE. THE RPTR STATED ONLY 1 OF 6 LATCHES WERE HOLDING THE LOWER COWLING. THE RPTR SAID THE AIRPLANE WAS GIVEN A THOROUGH WALKAROUND PREFLT CHK AND THE COWLING WAS UNLATCHED ONLY TO CHK AND SVC THE OIL ON BOTH ENGS. THE RPTR STATED THE COWLING WAS LATCHED AND CHKED PRIOR TO DEP. THE RPTR SAID THE AIRPLANE WAS 3 HRS INTO THE FLT WHEN THE COWLING DEPARTED THE ACFT. THE RPTR STATED HE BELIEVES THE FAA PRELIMINARY FINDING WAS COWLING LATCH FAILURE.