Incident Overview
During a descent through 8,000 feet at 120 mph, the airplane experienced flutter of the empennage. The pilot reduced engine power, causing the flutter to subside, and subsequently landed without further incident.
Inspection Findings
Examination of the empennage disclosed cracks at the four corners of the bulkhead at fuselage station (FS) 256.9. Adjacent to the damaged bulkhead, buckling of the fuselage skin was also noted.
Ruddervator Balance Check
The ruddervators, which had previously been reskinned, painted, and balanced, were removed from the airframe and balance-checked in accordance with the Bonanza 35 Series Shop Manual. The left ruddervator exhibited a static underbalance moment (trailing edge heavy) of 20.78 inch-pounds, and the right ruddervator exhibited 21.76 inch-pounds. According to the shop manual, the required static underbalance range is 16.80 to 19.80 inch-pounds, indicating that both ruddervators were out of the specified tolerance.
Conclusion
The incident involved empennage flutter, bulkhead cracking, skin buckling, and ruddervator imbalance beyond specified limits. No other causal factors were identified in the source.