Narrative:

Right engine nacelle outside access panel separated from nacelle during cruise flight, struck vertical and horizontal stabilizers, causing skin damage and failure of tail deice boots. No noticeable control differences. Thud and shutter felt when panel impacted tail performance and handling normal before and after. On duty feb/fri/03 at XA20L. Final 2 return legs delayed in ZZZ due to 2 maintenance items, one of which was the right ice light inoperative. At approximately XL30L, the mechanic, who is very experienced, skilled, and trusted, said the repairs were complete. I preflted the aircraft, including a walk around with a flashlight. I noted that the right engine access panel was in place and appeared normal and secure as I checked the aircraft exterior. This was the shadowed side of the aircraft, and it was freshly deiced and coated and dripping with type I deice fluid. I did not closely or individually inspect each fastener as I saw nothing protruding, and the panel appeared flush, in place, and secure. My walkaround was a normal, thorough, mid-shift review of the aircraft. Nothing appeared out of place or abnormal. Other aircraft in the area had reported mixed and clear icing, and moderate icing was reported. Shortly after passing just to the north of the ZZZ VOR, we heard and felt a dull thud that made the aircraft yaw slightly to the right for a second, then all returned to normal. It sounded like a bird strike from beneath the captain's seat. The captain checked fluid levels and pressures while flying, and I looked out my window at the right engine and wing. All appeared normal from my window. Even the ice light was shining normally on the wing. I then took the controls while the captain looked out his window for damage. Again, non observed. The captain took the controls back, and we discussed possibilities and how we would handle any system abnormalities. The captain then began a thorough chkout of all aircraft system, and I obtained the WX for ZZZ1. The captain discovered that our tail deice annunciator was not indicating that the tail boots were inflating. Pneumatic pressure and the other boots all checked out ok, so we decided that we must operate as if our tail deice was inoperative, and we could possibly have more tail or other unknown damage. Prior to the 'thud,' there was no indication of a problem. The only abnormality after that was the failed tail deice annunciator, which we know was working on climb out. There were 17 passenger on board this 19 seat aircraft. 16 were bound for ZZZ1 and only 1 for ZZZ2. I informed ATC that we may be diverting to ZZZ2, and received permission to slow and stay at 10000 ft while we contacted dispatch. The captain informed dispatch of the situation, that although the aircraft was performing and handling normally, and that we could not see any damage, we were concerned about the lack of tail deice combined with the WX in ZZZ1. Approach and landing were normal and we did successfully avoid any additional ice accumulation. Upon deplaning the passenger, all noticed the skin damage to the vertical stabilizer, the right horizontal stabilizer and its boot. After getting the passenger into the terminal, I performed my postflt walkaround and discovered the right engine access panel missing. The top row of fasteners was mostly torn off, and the other 3 sides were unharmed. A mechanic later found a fastener wedged in the vertical stabilizer area of impact, and it appears that this panel separated in flight, struck the vertical stabilizer, cut the boot, and hit the underside of the right horizontal stabilizer. It also appears that the sides and bottom of the panel were not securely fastened with all fasteners.

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Original NASA ASRS Text

Title: A BEECH 1900D IN CRUISE AT 10000 FT DIVERTED DUE TO A 'THUD AND SHUTTER' WITH THE TAIL DEICING FAILURE WARNING ILLUMINATED. CAUSED BY NACELLE PANEL DEPARTING ACFT.

Narrative: R ENG NACELLE OUTSIDE ACCESS PANEL SEPARATED FROM NACELLE DURING CRUISE FLT, STRUCK VERT AND HORIZ STABILIZERS, CAUSING SKIN DAMAGE AND FAILURE OF TAIL DEICE BOOTS. NO NOTICEABLE CTL DIFFERENCES. THUD AND SHUTTER FELT WHEN PANEL IMPACTED TAIL PERFORMANCE AND HANDLING NORMAL BEFORE AND AFTER. ON DUTY FEB/FRI/03 AT XA20L. FINAL 2 RETURN LEGS DELAYED IN ZZZ DUE TO 2 MAINT ITEMS, ONE OF WHICH WAS THE R ICE LIGHT INOP. AT APPROX XL30L, THE MECH, WHO IS VERY EXPERIENCED, SKILLED, AND TRUSTED, SAID THE REPAIRS WERE COMPLETE. I PREFLTED THE ACFT, INCLUDING A WALK AROUND WITH A FLASHLIGHT. I NOTED THAT THE R ENG ACCESS PANEL WAS IN PLACE AND APPEARED NORMAL AND SECURE AS I CHKED THE ACFT EXTERIOR. THIS WAS THE SHADOWED SIDE OF THE ACFT, AND IT WAS FRESHLY DEICED AND COATED AND DRIPPING WITH TYPE I DEICE FLUID. I DID NOT CLOSELY OR INDIVIDUALLY INSPECT EACH FASTENER AS I SAW NOTHING PROTRUDING, AND THE PANEL APPEARED FLUSH, IN PLACE, AND SECURE. MY WALKAROUND WAS A NORMAL, THOROUGH, MID-SHIFT REVIEW OF THE ACFT. NOTHING APPEARED OUT OF PLACE OR ABNORMAL. OTHER ACFT IN THE AREA HAD RPTED MIXED AND CLR ICING, AND MODERATE ICING WAS RPTED. SHORTLY AFTER PASSING JUST TO THE N OF THE ZZZ VOR, WE HEARD AND FELT A DULL THUD THAT MADE THE ACFT YAW SLIGHTLY TO THE R FOR A SECOND, THEN ALL RETURNED TO NORMAL. IT SOUNDED LIKE A BIRD STRIKE FROM BENEATH THE CAPT'S SEAT. THE CAPT CHKED FLUID LEVELS AND PRESSURES WHILE FLYING, AND I LOOKED OUT MY WINDOW AT THE R ENG AND WING. ALL APPEARED NORMAL FROM MY WINDOW. EVEN THE ICE LIGHT WAS SHINING NORMALLY ON THE WING. I THEN TOOK THE CTLS WHILE THE CAPT LOOKED OUT HIS WINDOW FOR DAMAGE. AGAIN, NON OBSERVED. THE CAPT TOOK THE CTLS BACK, AND WE DISCUSSED POSSIBILITIES AND HOW WE WOULD HANDLE ANY SYS ABNORMALITIES. THE CAPT THEN BEGAN A THOROUGH CHKOUT OF ALL ACFT SYS, AND I OBTAINED THE WX FOR ZZZ1. THE CAPT DISCOVERED THAT OUR TAIL DEICE ANNUNCIATOR WAS NOT INDICATING THAT THE TAIL BOOTS WERE INFLATING. PNEUMATIC PRESSURE AND THE OTHER BOOTS ALL CHKED OUT OK, SO WE DECIDED THAT WE MUST OPERATE AS IF OUR TAIL DEICE WAS INOP, AND WE COULD POSSIBLY HAVE MORE TAIL OR OTHER UNKNOWN DAMAGE. PRIOR TO THE 'THUD,' THERE WAS NO INDICATION OF A PROB. THE ONLY ABNORMALITY AFTER THAT WAS THE FAILED TAIL DEICE ANNUNCIATOR, WHICH WE KNOW WAS WORKING ON CLBOUT. THERE WERE 17 PAX ON BOARD THIS 19 SEAT ACFT. 16 WERE BOUND FOR ZZZ1 AND ONLY 1 FOR ZZZ2. I INFORMED ATC THAT WE MAY BE DIVERTING TO ZZZ2, AND RECEIVED PERMISSION TO SLOW AND STAY AT 10000 FT WHILE WE CONTACTED DISPATCH. THE CAPT INFORMED DISPATCH OF THE SIT, THAT ALTHOUGH THE ACFT WAS PERFORMING AND HANDLING NORMALLY, AND THAT WE COULD NOT SEE ANY DAMAGE, WE WERE CONCERNED ABOUT THE LACK OF TAIL DEICE COMBINED WITH THE WX IN ZZZ1. APCH AND LNDG WERE NORMAL AND WE DID SUCCESSFULLY AVOID ANY ADDITIONAL ICE ACCUMULATION. UPON DEPLANING THE PAX, ALL NOTICED THE SKIN DAMAGE TO THE VERT STABILIZER, THE R HORIZ STABILIZER AND ITS BOOT. AFTER GETTING THE PAX INTO THE TERMINAL, I PERFORMED MY POSTFLT WALKAROUND AND DISCOVERED THE R ENG ACCESS PANEL MISSING. THE TOP ROW OF FASTENERS WAS MOSTLY TORN OFF, AND THE OTHER 3 SIDES WERE UNHARMED. A MECH LATER FOUND A FASTENER WEDGED IN THE VERT STABILIZER AREA OF IMPACT, AND IT APPEARS THAT THIS PANEL SEPARATED IN FLT, STRUCK THE VERT STABILIZER, CUT THE BOOT, AND HIT THE UNDERSIDE OF THE R HORIZ STABILIZER. IT ALSO APPEARS THAT THE SIDES AND BOTTOM OF THE PANEL WERE NOT SECURELY FASTENED WITH ALL FASTENERS.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.