Empennage Flutter During Smooth Flight Results in Substantial Damage (N511B)

Incident Overview

During flight in smooth air, the empennage of an aircraft experienced flutter, leading to substantial damage to the aft fuselage and bulkheads near the ruddervator attachment points. The incident occurred without any reported turbulence or other atmospheric disturbances.

Examination Findings

Post-accident examination included static balance tests on both ruddervator surfaces. The tests disclosed that the static balance of both ruddervators was excessively tail-heavy. Additionally, there was evidence that the ruddervator surfaces had last been painted while still attached to the airplane. The thickness of the primer and paint applied during this process exceeded the manufacturer's factory acceptance criteria.

Damage Assessment

Substantial damage was observed in the aft fuselage and bulkheads in the vicinity of the ruddervator attachment points. The flutter resulted in structural deformation and compromised integrity in these areas.