Preflight and Approach Briefing
Before the flight, the pilot was informed that the ILS glideslope for runway 8R at the destination airport (SUS) was out of service. During a night arrival, the approach controller asked the pilot if he wanted an IFR clearance, and the pilot accepted. The controller provided vectors for an ILS runway 8 right approach but cleared the pilot for the approach without advising that the glideslope remained out of service. Additionally, the controller did not assign an IFR transponder code, which prevented the low altitude alert system from activating.
Approach Sequence
During the initial approach, the pilot flew through the localizer course and then reported that he was not receiving the localizer. The approach controller asked the tower if the localizer was operational; the tower responded that it was in alarm but that the localizer was up at that moment. The pilot was then re-vectored for the approach and subsequently reported that he was receiving the localizer. He was cleared again for the ILS approach.
Descent and Collision
During the approach, aircraft N9187M descended below the localizer-only minimum descent altitude of 1,020 feet and the ILS decision height of 662 feet. The airplane subsequently struck trees on an island in a river, approximately 2.5 miles west of the airport. The river was below the airport elevation, which is 463 feet.