Originally Posted by
john_tullamarine
More often it is the phugoid natural mode of motion that needs to damped out in order to allow the autopilot to achieve accurate height hold control.
By definition (assuming significant bits of the aircraft haven't fallen off or stopped working) , the phugoid is a long period minor nuisance pussy cat sort of problem and ought to need no outside assistance ... the SPO, however, can be a different animal.
Good Lord, John, not the phugoid again!