Approach and Missed Approach
The first officer was flying the instrument landing system (ILS) approach to Salt Lake City (SLC). Fog seeding was in progress, causing variable visibilities. The approach began with runway visual range (RVR) well above Category I minima. At decision height (DH), the captain called out 'LIGHTS IN SITE'. The first officer continued the descent through DH. The aircraft then re-entered instrument meteorological conditions (IMC), and the captain called for a missed approach. The first officer added power and established a wings-level, 10-degree nose-up attitude on the gyro horizon while the captain executed checklist items.
Contact with Antenna
The captain then noted that the aircraft was heading 20 degrees right of course and had a right-wing-down attitude on his gyro horizon. He called 'TURN LEFT AND PULL UP'. The aircraft's left main landing gear contacted a 45-foot-high ILS antenna stack located 1,049 feet down the runway, 400 feet right of the centerline. This contact separated the left main gear. The aircraft diverted to Pocatello Regional Airport (PIH), where additional damage was sustained during landing.
Equipment Findings
Post-incident tests revealed that the first officer's gyro horizon had bad bearings and the 'OFF' flag was inoperative. Additionally, the first officer's altimeter read 100 feet high.