What happened
A Short Brothers SD3-60 cargo flight was being vectored for the VOR/DME RWY 28R approach to Billings Logan International Airport under instrument meteorological conditions. One minute prior to the accident, weather conditions consisted of winds from 020 at 13 knots, light snow, and mist, with visibility rapidly deteriorating.
The crew was operating with the co-pilot in the right seat flying the aircraft and the pilot in command (PIC) handling radio communications. At 0812:25, after crossing the final approach fix, the aircraft descended through 100 feet above the MDA (3,940 feet or 426 feet above the runway threshold). Immediately following this descent, the crew visually acquired the runway.
At 0813:01, the aircraft's GPWS issued a 'SINK RATE' alert. Two seconds later, the PIC called for 'POWER,' and two seconds after that call, the aircraft impacted the ground. During the impact, the left main landing gear collapsed due to overload.
Findings
Records indicated the co-pilot had logged 103 hours in the Short Brothers SD3-60, all within the previous 90 days. The PIC had recently transitioned to flying the aircraft in Montana's late fall weather following a six-year assignment in the Hawaiian Islands.