ATL96LA132

Flutter of the empennage occurred as the airplane was descending through 8,000 feet at 120 mph. The flutter subsided when the pilot reduced engine power, and he subsequently landed without incident. Examination of the empennage disclosed that the bulkhead at fuselage station (FS) 256.9 exhibited cracks at the four corners of the assembly. Also, buckling of the fuselage skin was noted adjacent to the damaged bulkhead. The ruddervators, which previously had been reskinned, painted, and balanced, were removed from the airframe and balance checked in accordance with the Bonanza 35 Series Shop Manual. The left and right ruddervators exhibited static underbalance moments (trailing edge heavy) of 20.78 and 21.76 inch-pounds, respectively. According to the shop manual, the required static underbalance range is 16.80 to 19.80 inch pounds.

About February 22, 1996, at 1600 eastern standard time, a Beech 35, N3134V, experienced the failure of the aft bulkhead in the empennage section of the airframe while on approach to the Griffin-Spalding County Airport in Griffin, Georgia. The business flight operated under the provisions of Title 14 CFR Part 91 with no flight plan filed. According to the pilot, visual weather conditions prevailed at the time of the accident. The airplane sustained substantial damage. The private pilot and his passenger were not injured. The flight departed Orlando, Florida, at 1100.

According to the pilot, while on descent from 10,000 feet, they experienced flutter in the aft section of the airframe. When the pilot reduced engine power, the flutter episode stopped. The pilot continued the approach to Griffin, and landed without incident. The visual examination of the empennage section disclosed that the airframe had sustained structural damage that wrinkled the skin in the vicinity of both ruddervator and stabilizer assemblies.

An examination of the internal structural components of the empennage disclosed that the bulkhead at fuselage station (FS) 256.9 exhibited cracks at the four corners of the assembly. In the immediate vicinity of the damaged bulkhead, there was buckling to the aft fuselage skin. The remainder of the aft portion of the empennage was not damaged, including the ruddervator assemblies.

The ruddervators were removed from the airframe and balance checked in accordance with the Bonanza 35 series Shop Manual. The left and right ruddervators exhibited static underbalance moments of 20.78 and 21.76 inch-pounds respectively. The required static balance range is 16.80 to 19.80 inch pounds. The right and left ruddervator counterweight assemblies weighed 2.45 and 2.44 pounds.

A review of the airframe maintenance logs disclosed that the last ruddervator reskinning, painting and balancing were accomplished on June 18, 1991. The maintenance log review also disclosed that Airworthiness Directive (AD) 94-20-04 was accomplished during the last annual inspection. AD 94-20-04, required a balance check of the ruddervator assemblies within the next one hundred hours time-in-service after the effective date of the AD. Additionally, the requirements of the AD apply when the ruddervator assemblies have been reskinned or painted.