The Metro III departed Buenos Aires-Aeroparque on a cargo flight to Posadas via Sauce Viejo. At 07:03 the flight contacted the Sauce Viejo Approach controller. They were informed that weather was below minima with calm wind, visibility 30 meters reduced by fog, temperature 8 deg. C, QNH 1024 hPa. At 07:14 the crew contacted Sauce Viejo Tower and were again informed that the weather was below minima. The pilot then wanted to attempt the approach until decision height. They were cleared for an ILS runway 03 approach. Minima for that approach included 900 metres visibility and a 224 feet decision height. At 07:20 the flight reported having captured the localizer at 3000 feet. The controller gave approach clearance and requested the crew to report overhead the Outer Marker (OM). After reporting over the OM, the crew had to report when over the Middle Marker (MM) or when they had the runway in sight. The aircraft descended below minimum descent altitude and contacted terrain 430 meters short of the runway. The undercarriage collapsed as the airplane skidded another 180 metres before coming to rest. CAUSA: “Descender por debajo de los m¡nimos establecidos durante una aproximaci¢n por instrumentos e impacto contra el terreno. Factores contribuyentes: – Inadecuada planificaci¢n del vuelo, dado que el AD Sauce Viejo se mantuvo con la visibilidad reducida desde las 01:00 hs. – Requerimiento inapropiado del Comandante de Aeronave, para hacer un intento de aproximaci¢n con las condiciones meteorol¢gicas por debajo de los m¡nimos. – Decisi¢n err¢nea del Comandante de Aeronave, conociendo las condiciones meteorol¢gicas, para continuar la aproximaci¢n por debajo de la altitud de decisi¢n.” PROBABLE CAUSE: “Descended below the established minima during an instrument approach and impacted terrain.” Contributing factors were: – Inadequate flight planning, since there was reduced visibility at Sauce Viejo Airport from 01:00 hrs – Inappropriate request of the captain, to make an attempt of approach with the meteorological conditions below minima. – Erroneous decision of the captain, knowing the meteorological conditions, to continue the approach below the decision height.”