SEA96LA181

About five minutes after takeoff, at 6,500 feet, the 1947 model airplane was cruising at 160 to 165 knots, when it encountered turbulence and experienced an airframe vibration. The pilot reduced airspeed, which eliminated the vibration, then he landed without further incident. Subsequent examination revealed that the fuselage station 256.9 bulkhead, located directly below the leading edge of the V-tail, was cracked at all four corners. Further investigation revealed that the airplane's ruddervators had been removed in 1995 for reskinning due to corrosion. Reskinning was accomplished with Beech factory replacement skins, and the ruddervators were then painted with several layers of paint. This necessitated the installation of an additional one-pound (lead) weight on the outboard tip of each ruddervator to achieve correct control surface balance. Also, the pilot stated that he could not be sure whether the station 256.9 bulkhead was damaged in flight, or when the ruddervator contacted a hangar support beam as the airplane was being pushed in a hangar.

On August 1, 1996, a Beech 35, N2839V, encountered turbulence and experienced a subsequent airframe vibration at 160 to 165 knots airspeed and 6,500 feet altitude approximately five minutes after takeoff from Felts Field, Spokane, Washington, en route to Colville, Washington. The private pilot, who was not injured in the occurrence, reduced airspeed (which eliminated the vibration) and returned to Felts Field, where he landed without further incident. A subsequent airframe examination revealed that the fuselage station 256.9 bulkhead, located directly below the leading edge of the V-tail, was cracked at all four corners. The pilot reported to an FAA inspector from Spokane, Washington, that visual meteorological conditions prevailed at the time of the turbulence encounter. The time of the occurrence was not reported.

The FAA aircraft registry indicated that the airplane was manufactured in 1947. FAA inspectors determined that the aircraft's ruddervators were removed in 1995 for reskinning due to corrosion. Reskinning was accomplished with Beech factory replacement skins and the ruddervators were then painted with several layers of paint, necessitating an additional pound of lead weight to be added to the outboard tip of each ruddervator in order to achieve correct control surface balance. Discussions with the Spokane FAA inspector assigned to the accident indicated that the one-pound weights were installed in addition to the parts specified by the aircraft maintenance manual for balancing the ruddervators, and were not an approved installation per the aircraft maintenance manual. The aircraft maintenance manual allows up to 11 lead washers of unspecified weight to be used in balancing the ruddervators. The Spokane FAA inspector reported that an examination of the ruddervators revealed them to be correctly balanced with the non-approved one-pound weights installed.