Hydraulic and Pneumatic Power Systems Which is true regarding the ground check of a flap operating mechanism which has just been installed? a. If the time required to operate the mechanism increases with successive operations, it indicates the air is being worked out of the system. b. If the time required to operate the mechanism decreases with successive operations, it indicates the air is being worked out of the system. c. All hydraulic lines and components should be checked for leaks by applying soapy water to all connections.