Medium Transport
Flight Crew Air Transport Pilot (ATP)
Situational Awareness
Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Unstabilized Approach
General None Reported / Taken
Human Factors; Weather
While completing a monitored CAT II approach; we broke out at approximately 150 feet above min. Controls were transferred at which point the autopilot was also disconnected by the Captain. Visibility was very good. I transitioned my vision outside to monitor the visual approach and noticed we were pitching down. From my point of view I assumed we were maneuvering to maximize full length of runway 28. As a result we received a sink rate GPWS.  The captain over corrected slightly; at which point we received the stick shaker. At the stick shaker; the captain momentarily increased thrust to go-around power and back to idle. We landed in the touchdown zone.At the point the decision to go around was made by the captain; I should not have hesitated to continue with the decision.Go Around at any time during the approach in which continuing might end in an undesired outcome!
The first officer executed a perfect approach and I made the 'visual' call well above minimums for the approach. I assumed control of the aircraft.As the aircraft was crossing into the airport property at TRI; the glideslope began to rapidly sink to the bottom of the PFD. At this time; I increased the rate of descent in a futile effort to recapture the glideslope. Shortly thereafter; the 'SINK RATE' aural sounded. I slightly increased power and significantly increased the aircraft's angle of attack in an effort to salvage what I thought would be a smooth landing. Instead; as the aircraft was in the flare; the stick shaker unexpectedly activated.This caught me by surprise. I was not expecting the stick shaker.I held the aircraft in the flare and continued the landing and taxied to the gate uneventfully.The threats were multiple. It was an early morning van time to the airport; and; the event occurred on the last day of a 4 day trip. The day of the event was very close to the absolute maximum Flight Duty Period allowed; I was aware of; and inwardly concerned; that a go-around would put us into a position of having to accept an extension to our FDP to complete the day. I was eager to complete the trip; and; to not have to put the FO in a position of having to determine fitness for duty after a long day. The error was twofold. I should not have destabilized the aircraft once the airport environment was in sight. (There was a note on the approach plate that mentioned that the glideslope was unusable inside of the airport boundary.) Also; once the aircraft was unstable; I should have executed a go-around. While the events unfolded much quicker than I had imagined; my reaction was extremely slow.The undesired state was the aircraft being in an unstable position just above the runway.
Air carrier flight crew reported getting a stick shaker at low altitude on a monitored Cat II Approach. Captain chose to continue to an uneventful landing.