What happened
On January 20, 2003, a Piper PA-44-180, registration OK-MLR, was conducting an IFR flight for the purpose of qualification training. Shortly after takeoff from Prague Airport, the aircraft's course guidance system failed. The pilot identified the discrepancy when attempting a course change that did not align with the expected heading for Runway 31.
Upon realizing the failure, the commander immediately notified Prague Radar control and requested radar vectors for an ILS approach to Runway 31. However, during the approach, both the NAV 1 and NAV 2 navigation units provided unreliable Glideslope (GS) indications. At this stage, the aircraft was approximately 7 NM from the threshold of Runway 31. Given that weather conditions were within Visual Meteorological Conditions (VMC), the pilot requested and was granted a visual approach. The aircraft landed safely without any damage to the airframe or injuries to the crew.
The investigation
The ÚZPLN investigation focused on the simultaneous failure of the aircraft's guidance and navigation capabilities. The investigation established that the instructor pilot was properly qualified and medically fit for the flight, and that the meteorological conditions at the time were suitable for flight. The investigation also noted that the aircraft had undergone a radio-navigational equipment check in September 2002, which had confirmed its airworthiness for IFR operations. Following the incident, the aircraft was sent to a maintenance facility to address the technical malfunctions.
Findings
- The primary cause of the serious incident was the failure of the course guidance system and the unreliable Glideslope indications provided by both the NAV 1 and NAV 2 navigation units.
- The crew successfully transitioned to a visual approach to mitigate the risks posed by the unreliable instrument data.