What (a) investigations have been undertaken by the South African Civil Aviation Authority in the (i) 2012-13, (ii) 2013-14 and (iii) 2014-15 financial years, (b) were the respective dates of (i) the incidents into which investigations were launched, (ii) the commencement and (iii) conclusion of each investigation, and (c) measures have been put in place to prevent repetitions of such incidents in future, if not, why not; if so, what are the relevant details?