What happened
The aircraft owner ferried the plane VFR to a location for maintenance. Radios were repaired, but the glide slope receiver was found inoperative at a fuel stop. Weather forecasts indicated IFR conditions at the destination. The owner hired an IFR instructor for the remainder of the flight and showed the work order to the CFI. The instructor incorrectly concluded the glide slope had been fixed. He recalled the forecast ceiling was 600 feet but had no record of current weather showing a 200-foot ceiling and 1.25-mile visibility before the approach. The CFI stated he used a 500 FPM descent at 90 knots for the ILS Runway 36 approach. He told the owner that localizer and glide slope needles were centered two miles from the runway.
The investigation
Post-crash testing of the aircraft's avionics revealed critical discrepancies between the pilot's perception and the actual equipment status. While the CFI believed he was tracking a valid glide path, the hardware required to provide vertical guidance was not functioning. This mechanical failure meant that any indication of being on the correct descent angle was false.
Findings
The primary error stemmed from a misinterpretation of maintenance documentation. The instructor relied on a work order rather than verifying system functionality or obtaining current weather data. He proceeded with an instrument approach in conditions significantly worse than the forecasted minimums, relying on a glide slope receiver that was confirmed to be inoperative. This lack of situational awareness regarding both the aircraft's airworthiness and the actual atmospheric conditions led directly to the accident.
Safety message
Pilots must verify the operational status of critical navigation equipment through functional checks, not just maintenance records. Additionally, obtaining current weather reports prior to any approach is essential, as forecasts can differ significantly from reality.