During an approach at Exeter Airport, the aircraft became unstable after the point where the crew had declared the approach stable and continued. During the final 500 ft the rate of descent exceeded the required 500 ft stable approach criteria on four occasions. All bar the first of these excursions were accompanied by GPWS “SINK RATE” alert. The subsequent hard landing resulted in extensive damage to the aircraft. There were no injuries.
The operator has taken safety action to reinforce its operating procedures with regards to the criteria for a stable approach.