Date: 201208
Local time of day: 0601-1200
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Light: Daylight
Aircraft: Cessna Citation Sovereign (C680)
Operator: Fractional
Operating under: Part 91
Flight phase: Descent
Airspace: Class E ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Pylon Fasteners & Latches
Component problem: Improperly Operated
Reporter organization: Fractional
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Other / Unknown
Second reporter function: Pilot Not Flying; Captain
Anomaly: Aircraft Equipment Problem Critical; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Crew
When detected: In-flight
Result: Aircraft Aircraft Damaged; Flight Crew Diverted; Flight Crew Landed in Emergency Condition; General Declared Emergency; General Maintenance Action
Contributing factors: Aircraft; Human Factors; Procedure
Primary problem: Ambiguous

Narrative: I was the SIC; and we picked the plane up at the service center. I was pilot flying and occupying the left seat. We were ferrying the plane to pick up a passenger. Pre-flight; engine start; taxi; take-off; climb; and all related checklists were normal. On descent to 17;000 FT; and passing FL190; we heard a muffled bang. There was a shudder followed by continuous vibration. I immediately began to reduce power to slow down. There were no CAS messages displayed and engine instruments and pressurization all remained normal. We decided that the Captain would call the company and I would fly and communicate with ATC. Center gave us a further descent to 11;000. Maintenance decided we needed to divert. I informed Center of the change of destination. They wanted us to climb to 14;000 FT for the new route. Climbing through 12;000 we both noticed a funny odor and the vibration was getting worse. I requested a level off at 12;000 and that was granted. We proceeded to a divert station; declaring an emergency due to vibration from an unknown source. We configured early in case there was an issue with the gear or flaps. We landed without incident and taxied off and clear of the runway and came to a stop close to the emergency vehicles. We had contact with them and they told us we had significant damage to our right engine. We shut down right there and were later towed to the Service Center. We found much of the underside cowling of the right engine missing.


Second narrative: I was PIC and was pilot not flying for this day's legs. The First Officer accomplished an exterior inspection while I got the flight plan for this leg and the next leg and the plane was fueled. Nothing unusual was noted on the exterior and interior preflight except for a low oil message on the right engine. I went back into the hangar and asked that 1/2 quart be added to the engine. After insuring that the oil was added and the oil service was closed I walked around the aircraft to insure that every thing was locked/latched. Nothing was noted. Takeoff [before sunrise]; climb out (to FL370); and cruise were normal. During descent; between FL180 and 17;000; we both heard a loud bang followed by a low vibration and rumbling. We checked all the systems and the engine indications and everything was normal. We both discussed the situation and decided that I would call Maintenance and the Assistant Chief Pilot. The First Officer took over communication in addition to his flying duties. During the call Maintenance and the Assistant Chief Pilot decided that we should divert. I was put in contact with Dispatch and our release was amended. While I was obtaining the new release; the First Officer told Center that we needed to divert. Our main concern was that we had a gear problem even though all indications were normal. When I finished the call to Headquarters I took over pilot not flying duties. We were handed off to another Center Frequency and I declared an emergency. When I contacted Approach I again declared an emergency. By this time all the checklist were accomplished and we were cleared for an ILS at our divert station. The First Officer started configuring early; flap and gear extension were normal. Landing was normal but as we retracted the thrust reversers we got an engine control fault R CAS message. After we cleared the runway we stopped so the fire trucks could inspect the airplane. As they looked at the airplane it was recommended that we shut down engines because we had extensive damage to the right engine. We shut the engines and the rest of the airplane down and exited; normally; to look at the right engine. That was when we saw that most of the bottom of the right engine cowling was missing. I contacted Headquarters and we waited for Cessna to come to inspect the engine. After the inspection we were towed to the Service Center.


Synopsis: CE680 flight crew experiences a loud bang followed by a low vibration and rumbling during descent for landing. All indications in the cockpit are normal but the crew diverts for maintenance at the company's request. Post flight revealed that most of the bottom of the right engine cowling was missing.