When an autopilot fails to move the rudder, the fault may be rooted in the autopilot course computer, drive units, or rudder reference transducer. Should the autopilot course computer be interfaced to a rudder reference transducer, then click here to view the FAQ addressing how to test a rudder reference transducer. When using a rudder reference transducer, it is also very important to ensure that rudder limits have been correctly configured to establish angular limits to the amount of rudder travel and to ensure that the rudder angle indicator correctly indicates the position of the rudder with respect to the centered position.
Drive units feature reversible DC motors. The clutch of a drive unit is tested by placing the autopilot into Auto and then Standby. Should the drive not release and the drive unit's clutch lead be properly connected to the autopilot course computer of Evolution autopilot ACU, then the drive unit may have suffered a Clutch failure. A properly functioning drive until will engage the clutch (causes the drive to lock) when 12 VDC is present across the Clutch leads. Similarly, a properly functioning drive until will release the clutch (causes the drive disengage) when 12 VDC is not present across the Clutch leads.
Should rudder reference transducer (if so equipped) be operating properly, then failures related to rudder movement may be fault isolated to the drive or autopilot course computer testing the drive unit's ability to move the rudder in each direction when driven by a source of power other than the autopilot course computer. To do so, disconnect the drive unit's motor leads from the autopilot course computer and instead momentarily connect then to a 12VDC power circuit or battery. This connection should be momentary in nature and only long enough to verify that the drive is able to move the rudder. After verifying movement of the rudder in on direction,
1) disconnect the drive unit's motor leads from the 12VDC power circuit or batter
2) connect the drive unit's motor lead which had been previously connected to -12VDC instead to +12VDC
3) connect the drive unit's motor lead which had been previously connected to +12VDC instead to -12VDC
4) verify that the drive unit moves the rudder in the opposite direction
Should the drive unit move the rudder in both directions, then the fault has been isolated to the autopilot's course computer, necessitating that it be serviced or replaced. Should the drive unit move the not rudder in both directions, then the fault has been isolated to the drive unit, necessitating that it be serviced or replaced.
CRAFAQ#
Drive units feature reversible DC motors. The clutch of a drive unit is tested by placing the autopilot into Auto and then Standby. Should the drive not release and the drive unit's clutch lead be properly connected to the autopilot course computer of Evolution autopilot ACU, then the drive unit may have suffered a Clutch failure. A properly functioning drive until will engage the clutch (causes the drive to lock) when 12 VDC is present across the Clutch leads. Similarly, a properly functioning drive until will release the clutch (causes the drive disengage) when 12 VDC is not present across the Clutch leads.
Should rudder reference transducer (if so equipped) be operating properly, then failures related to rudder movement may be fault isolated to the drive or autopilot course computer testing the drive unit's ability to move the rudder in each direction when driven by a source of power other than the autopilot course computer. To do so, disconnect the drive unit's motor leads from the autopilot course computer and instead momentarily connect then to a 12VDC power circuit or battery. This connection should be momentary in nature and only long enough to verify that the drive is able to move the rudder. After verifying movement of the rudder in on direction,
1) disconnect the drive unit's motor leads from the 12VDC power circuit or batter
2) connect the drive unit's motor lead which had been previously connected to -12VDC instead to +12VDC
3) connect the drive unit's motor lead which had been previously connected to +12VDC instead to -12VDC
4) verify that the drive unit moves the rudder in the opposite direction
Should the drive unit move the rudder in both directions, then the fault has been isolated to the autopilot's course computer, necessitating that it be serviced or replaced. Should the drive unit move the not rudder in both directions, then the fault has been isolated to the drive unit, necessitating that it be serviced or replaced.
CRAFAQ#