Incident Overview
An aircraft encountered moderate to severe icing during flight. The pilot believed that the ice had been shed after cycling the deice boots, observing ice coming off the wings. However, the pilot could not visually confirm whether ice had also cleared from the horizontal stabilizer.
Sequence of Events
On short final approach at 100 knots, the control yoke began to vibrate. In response, the pilot increased airspeed and lowered the nose, but was unable to flare the aircraft. This resulted in a hard landing.
Post-Event Findings
After landing, clear ice chunks were found on the runway. These were apparently pieces that broke off upon touchdown. An operational check of the deice boots, conducted at a later date, found that both the wing and horizontal stabilizer deice boot systems were functioning satisfactorily.