The Cessna FR172K aircraft, with one Pilot and one passenger on board, was en route from Rathcoole Aerodrome, Co. Cork (EIRT) to Tibohine Airfield, Co. Roscommon. When the aircraft was north-west of Loughrea, Co. Galway, the Pilot noticed that the engine oil pressure was decreasing and that some oily smoke had emanated from the engine cowlings. This was followed by the failure of the engine. The Pilot made a MAYDAY call to Shannon Air Traffic Control (ATC), to inform them of the situation and that he was going to carry out an emergency landing. During the attempted landing in an agricultural field, the aircraft contacted the ground hard and sustained substantial damage, resulting in the serious injury of the Pilot and passenger. The Pilot and passenger were assisted from the aircraft by two passers-by. There was no fire.