End of flight scenario
Note: Given the imprecise nature of the SATCOM data, it was necessary to make some assumptions regarding pilot control inputs in order to define a search area of a practical size. These assumptions were only made for the purposes of defining a search area and there is no suggestion that the investigation authority will make similar assumptions.
The limited evidence available for MH370 was compared with the accident classes listed previously.
In the case of MH370, there were multiple redundant communications systems fitted to the aircraft (3 x VHF radios, 2 x HF radios, SATCOM system, 2 x ATC transponders). However, no radio communications were received from the aircraft after 1719.29, 7 hours prior to the last SATCOM handshake at 00:19. Analysis of the SATCOM data also showed that there were probably no large changes to the aircraft’s track after approximately 1915, about 5 hours prior to the last SATCOM handshake.
Given these observations, the final stages of the unresponsive crew/ hypoxia event type appeared to best fit the available evidence for the final period of MH370’s flight when it was heading in a generally southerly direction:
Interesting turn of phrase in first paragraph. Obviously it is not the role of ATSB to speculate on possible earlier events. The role of ATSB is locating the plane if possible. The Malaysians are responsible for investigating the psssinlr cause.
Diplomatic protocol would also preclude ATSB from speculating along lines that could embarrass Malaysia.
So ATSB is appropriately not speculating on cause. Yet they had to make some assumptions in order to define the area. Hence the most "neutral" possible hypothesis.
Hopefully the model is not too constrained such that it does not encompass alternative explanations. In particular, the document makes some comments about possible gliding distance if there were control inputs. At 90 odd km, the search areaay not be "wide" enough to cover a controlled glide.