What happened
The aircraft impacted mountainous terrain at an altitude of approximately 1,800 feet, located roughly two miles south of the airport. The flight was cleared for the VOR-A approach procedure. According to the pilot's statement, the onboard Distance Measuring Equipment (DME) experienced intermittent functionality during the descent. The pilot believed he was encountering a 10-knot tailwind and consequently utilized a three-minute timing interval from the Final Approach Fix (FAF) to the Missed Approach Point (MAP).
Standard approach procedures indicate that a three-minute timing segment is appropriate for an aircraft with an approach speed of 120 knots. However, recorded radar data revealed that the aircraft's ground speed on final approach was significantly higher than expected, fluctuating between 169 and 184 knots. This excessive speed likely contributed to the aircraft passing the missed approach point without establishing visual reference.
Weather conditions at the time were severe. A witness located at the airport described the visibility as zero due to dense fog, with the ceiling reported as indefinite and obscured. The minimum descent altitude (MDA) for this procedure is 1,740 feet. The aircraft descended below this safe altitude while operating in instrument meteorological conditions without the required visual references.
The investigation
Investigators analyzed recorded radar data to determine the aircraft's performance during the final segment of the approach. The data confirmed that the ground speed was inconsistent with the pilot's timing calculations and standard approach speeds. The intermittent nature of the DME system was noted as a potential factor in the pilot's navigation errors, though the primary discrepancy lay in the airspeed management.
Findings
The crash was caused by the pilot's failure to maintain visual contact with the runway environment during an instrument approach in zero visibility conditions. Contributing factors included the use of excessive ground speed, which invalidated the standard timing-based navigation method, and the intermittent operation of the DME system. The aircraft was below the minimum safe altitude for the phase of flight while operating in fog.
Safety message
Pilots must ensure that approach speeds are consistent with published procedure timings. Deviating from specified airspeeds renders time-based navigation segments inaccurate. Additionally, reliance on intermittent navigation aids during low-visibility approaches requires heightened situational awareness and strict adherence to missed approach procedures if visual references are not acquired.