What happened
During a flight involving an instructor and a student pilot, the crew encountered weather conditions that were no longer suitable for visual flight rules (VFR). While the initial departure from Warrnambool was conducted under suitable conditions, the weather soon degraded. During the return leg to Warrnambool, the aircraft encountered forecast conditions that necessitated a climb, resulting in the aircraft entering cloud. The aircraft was not certified for instrument flight, and the instructor had not practiced instrument flying skills for eleven months. To manage the situation, the instructor minimized control movements and contacted air traffic control to request assistance, which helped maintain aircraft control and facilitated a return to visual conditions.
The investigation
The investigation focused on the pre-flight planning and the crew's assessment of meteorological forecasts. Although the crew reviewed weather forecasts during pre-flight planning, they failed to identify deteriorating weather forecast for area B on the GAF. Furthermore, because the flight departed more than 60 minutes after the initial weather updates were obtained, updated information was required but not utilized.
During the stop at Warrnambool, the instructor checked weather for the return leg but relied on the TAF for Warrnambool and surrounding airports rather than checking the area forecast or the Moorabbin TAF. This oversight meant the crew did not identify the predicted reduction in visibility and low-level cloud. Additionally, the instructor's plan to use Warrnambool as an alternate airport did not sufficiently account for the TEMPO forecast, which indicated conditions could drop below alternate minima requirements.