NTSB Identification: CHI97LA119.
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Accident occurred Tuesday, April 29, 1997 in LEXINGTON, KY
Probable Cause Approval Date: 12/31/1998
Aircraft: Beech D35, registration: N5985C
Injuries: 2 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The pilot reported that he made a climb to 7,500 feet and set his power to cruise at 160 mph. To remain clear of clouds, he started a descent to 6,500 feet. He experienced light turbulence, and the airplane began to vibrate and shake. After 10 to 15 seconds, the pilot pulled back on the throttle, and the vibration stopped. The pilot thought the vibration was engine related. He re-applied power for cruise, then the airplane started to shake again, but much more violently than the first occurrence. He reduced power and landed the airplane. The airplane's never exceed airspeed (Vne) was 203 mph, and the maximum cruise airspeed (Vno) was 160 mph. Inspection of the airplane revealed that the aft fuselage received extensive damage between fuselage station (FS) 256.9 and the 233.5 bulkhead. The longerons were bent downward, and two stringers were cracked. The left and right side fuselage panels below the stabilizers exhibited 45 degree buckling from the bottom of the FS 256.9 bulkhead to forward of the stabilizer cuffs. The bottom fuselage panel had popped rivets and torn skin, and there were two 2-inch creases in both stabilizers. No pre-existing cracks were found on the longerons. The ruddervators were properly balanced.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

flutter for an undetermined reason, which resulted in structural damage to the aft fuselage.

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