ATR-72, 16 October 2013, Lao Airlines Flight 301
The probable cause of this accident were the sudden change of weather
condition and the flight crew's failure to properly execute the
published instrument approach, including the published missed approach
procedure, which resulted in the aircraft impacting the terrain.
ATR-42, 19 October 2013, P2-PXY, Air Niugini
According to released information this cargo aircraft overran the runway after the crew aborted the take-off above Vr after experiencing pitch control problems. The final report of this accident is not yet published but a preliminary report is available. The investigation focusses on the payload distribution which may have caused imbalance leading to the perceived control problems.
ATR-72, 23 July 2014, TransAsia Airways Flight 222
The aircraft crashed on final approach in low visibility conditions (800 meters). During the initial approach the crew had requested and ILS approach (precision approach) to runway 02 but then changed their minds and asked for a VOR approach (non-precision approach) to runway 20. During the approach, after deactivation of the autopilot, the aircraft deviated 340 meters to the left and the crew subsequently announced they were going around. Shortly afterwards the aircraft hit tree tops and impacted residential buildings.
The final report is expected in October 2015.
To me it seems the probable cause is the failure of the flight crew to properly execute the published instrument approach including the published missed approach procedure which resulted in the aircraft impacting the trees and buildings.
ATR-72, 02 February 2015, TransAsia Airways Flight 235
The investigation into this accident is still running, only some preliminary information has been published. Preliminary data indicates that about 36 seconds after takeoff the engine no.2 auto-feathered, about 46 seconds subsequent to auto-feather the engine no.1 was shut off by the crew, resulting in loss of all thrust. The aircraft subsequently descended, stalled and crashed into a river.
ATR-42, 16 August 2015, Trigana Air Service Flight 257
This accident occurred just a couple of days ago so there are few facts known yet and no preliminary findings are published. I will not speculate about the probable cause of this accident.
The common thread in the first four accidents seems to be the failure to comply with established procedures resulting in the loss of the aircraft.
In two cases (Lao Airlines Flight 301 and TransAsia Airways Flight 222) the flight crew flew a controllable aircraft into the ground.
In the case of the Air Niugini crash improper loading of the aircraft is likely to be the cause, resulting in the aircraft being not trimmed correctly for take-off.
The crash of TransAsia Airways Flight 235 is the only crash that involved an aircraft system malfunction (engine 2 failure). However, the ATR-72 can fly on a single engine so the failure itself should not have been fatal. The crew then shut down the other engine (number 1) which sealed the aircraft's fate. It is too early to conclude that the crew didn't follow the correct procedures here; for example there may have been ambiguous indications from the engine instruments that led them to believe that engine no. 1 had failed. However with the information currently available it seems that the crew did not follow the correct procedures for shutting down a failed engine.
The high number of crashes involving an ATR aircraft seems not to be related to the model itself, but to the safety culture and lack of training within a number of airlines operating the aircraft.