Cracks And Malfunctions

During flight, the autopilot started to disconnect on the pilot. On the third attempt to engage the autopilot, the aircraft made a sudden, uncommanded 1500-fpm descent. The pilot used control-wheel steering and the autopilot disconnect button, but the autopilot would not disengage. He overpowered the autopilot to regain control; the autopilot remained on after he pulled the circuit breaker. He recycled the breaker and was successful in disconnecting the autopilot. The pilot also reported the electric trim switch seemed to work backwards. Maintenance personnel found water accumulated behind the rear curtain where the pitch servo is located.

Key Takeaways:

• A Cessna 208B Caravan experienced a critical autopilot malfunction, including an uncommanded 1500-fpm descent and disengagement failure, ultimately linked to water intrusion near the pitch servo.
• Engine failures included a Teledyne Continental engine's oil pump drive shaft shearing in cruise and Engine Components Inc. cylinder heads cracking, a known defect for which a service bulletin exists for earlier units.
• Other reported issues involved a Skytech starter repeatedly cracking its mount after installation and a Kelly heater combustion tube cracking, causing an air leak.

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