Incident Overview
A pilot was flying family members on a tour of the Sierra Nevada mountain range foothills when the flight encountered rapidly building cumulus clouds while cruising at an altitude of about 11,500 feet MSL. The pilot reported navigating around the buildups in an attempt to maintain visual flight rules (VFR) conditions, but the clouds eventually surrounded the aircraft.
Loss of Visual Reference
The flight inadvertently entered one of the large clouds. According to the pilot, the aircraft then entered a high-speed spiral dive, reaching an airspeed in excess of approximately 190 knots.
Recovery
The pilot stated that he, with the assistance of his son, began pulling back on the control wheel and successfully recovered control of the aircraft. Following the recovery, the flight returned to its home base and landed without further incident.
Post-Flight Examination
An examination of the aircraft by Federal Aviation Administration (FAA) inspectors revealed substantial structural damage. Both wings exhibited major buckles at the production joints between the inboard and outboard wing panels. The outboard panels showed an upward permanent set. Additionally, the fuselage immediately aft of the firewall and forward of the empennage displayed areas of skin buckling.
Conclusion
The aircraft sustained significant structural deformation as a result of the high-speed maneuver. The pilot's actions, with the help of his son, prevented a potential loss of control.