Incident Overview
A Short Brothers SD3-60 cargo flight was being vectored for the VOR/DME runway 28R approach to Billings Logan International Airport. The flight was conducted under instrument meteorological conditions.
Crew and Aircraft
The co-pilot, occupying the right seat, was flying the aircraft, while the pilot in command (PIC), occupying the left seat, was handling radio communications. The co-pilot had logged a total of 103 hours in the SD3-60, all within the previous 90 days. The PIC had just begun flying the aircraft in Montana's late fall weather after a six-year assignment flying in the Hawaiian islands.
Weather Conditions
One minute before the accident, weather conditions were reported as winds from 020 degrees at 13 knots, light snow and mist, and visibility deteriorating rapidly.
Sequence of Events
At 0812:25, having crossed the final approach fix, the aircraft descended through 100 feet above the minimum descent altitude (MDA), which is 3,940 feet or 426 feet above the runway threshold. Immediately thereafter, the crew visually acquired the runway.
At 0813:01, the aircraft's ground proximity warning system (GPWS) issued a "SINK RATE" alert. Two seconds later, the PIC called for "POWER," followed by a two-second delay before ground impact.
Damage
The left main landing gear collapsed in overload during the ground impact.