Propellers During operational check of an aircraft using hydromatic full-feathering propellers, the following observations are made: The feather button, after being pushed, remains depressed until the feather cycle is complete, then opens. When unfeathering, it is necessary to manually hold the button down until unfeathering is accomplished. a. Both feather cycle and unfeather cycle are functioning properly. b. Both feather and unfeather cycles indicate malfunctions. c. The feather cycle is correct. The unfeather cycle indicates a malfunction.