The aircraft was cleared for an ILS/DME approach to Runway 09 at Dundee Airport. Although it was raining and windy, the weather conditions were suitable for the approach. The pilot made a radio transmission reporting he was 4 nm to the west of the runway, on final approach, but the aircraft failed to arrive. A Search and Rescue helicopter located the aircraft wreckage on high ground 6.7 nm west of the airport. The investigation determined that it was likely that the instrument approach, carried out in IMC, was flown using range information based on the GPS distance from the ‘DND’ NDB, located 2.6 nm west of the airport, instead of using DME distance from the runway.