Incident Overview
An aircraft certificated for flight into known icing conditions up to moderate icing experienced an incident during an instrument approach. The pilot reported that the surface de-icers were operational during the preflight inspection.
Sequence of Events
While conducting an instrument approach at the destination, the aircraft entered clouds at approximately 4,400 feet MSL. Shortly after, ice began to accumulate on the airframe. The right engine started vibrating, and the vibration intensity continually increased. As the aircraft reached the runway, it descended from a higher than normal altitude and touched down hard.
Post-Flight Observations
After parking, a considerable amount of surface ice was still present on the aircraft. The pilot noted that the aircraft had a history of problems with the aircraft and propeller de-ice boots. During a subsequent ferry flight after the incident, the surface boots failed to operate. However, later during a ground check, the boots operated normally.
Aircraft Information
The aircraft was certified for operation in known icing conditions up to moderate icing. No other details about the aircraft type, registration, or operator were provided in the source.