The Irish AAIU released their investigation report regarding a serious incident in the Irish controlled airspace near Reporting Point BANBA at high level off the South East coast of Ireland.
Aircraft involved were an MD-83 routing northwards towards Dublin from Faro, and the a B737 routing westwards towards Cork from Stansted. The former was maintaining FL280, while the latter, which was cruising at FL300, was cleared initially by the Shannon Radar Controller to descend to FL290 and subsequently to FL100. This ATC clearance conflicted with the path of the northern bound aircraft, and, in spite of at least four warnings, one verbal and three electronic, the Radar Controller appeared not to comprehend the closing speeds of the two aircraft and allowed the higher one to descend and lose the required minimum vertical and lateral separation from the other. Each aircrafts on board TCAS automatically activated. The pilot of each aircraft reacted correctly to this TCAS warning, one climbed his aircraft as instructed by the system and the other descended his aircraft as instructed by the system. A potential mid-air collision was thus narrowly avoided due to the TCAS activation and the correct response of the pilots. They came within 600 feet of each other on the vertical plane. With separation subsequently re-established by ATC, both aircraft continued onwards and landed at their respective destinations. (AAIU)