Is the New ATSB Search Area Sound?

dstg-endpoint-probability-by-latitude

The above graph is taken from the DSTG book “Bayesian Methods in the Search for MH370, ” page 90. It shows the probability distribution of MH370’s endpoint in the southern Indian Ocean based on analysis of the different autopilot modes available to whoever was in charge of the plane during its final six hours. It was published earlier this year and so represents contemporary understanding of these issues. As you can see, the DSTG estimated that the probability that the plane hit the 7th arc north of 34 degrees south longitude is effectively zero.

I interviewed Neil Gordon, lead author of the paper, on August 11. At that time, he told me that experts within the official search had already determined that the BFO values at 0:19 indicated that the plane was in a steep descent, on the order of 15,000 feet per minute.

Such a rate of descent would necessarily indicate that the plane could not have hit the ocean very far from the 7th arc. Nevertheless, Fugro Equator, which was still conducting its broad towfish scan of the search area at the time, spent most of its time searching the area on the inside edge of the search zone in the main area, between 37.5 and 35 degrees south latitude, about 25 nautical miles inside the 7th arc. At no point between the time of our interview and the end of the towfish scan in October did Equator scan anywhere north of 34 degrees south.

Shortly thereafter, the ATSB hosted a meeting of the experts it had consulted in the course of the investigation, and the result of their discussion was published on December 20 of this year as “MH370 – First Principles Review.” This document confirms what Gordon told me, that the group believed that the BFO data meant that the plane had to have been in a steep dive at the time of the final ping. What’s more, the report specified that this implied that the plane could not have flown more than 25 nautical miles from the 7th arc, and indeed most likely impacted the sea within 15 nautical miles.

By the analysis presented above, a conclusion is fairly obvious: the plane must have come to rest somewhere south of 34 degrees south, within 25 nautical miles of the seventh arc. Since this area has already been thoroughly scanned, then the implication is that the plane did not come to rest on the Indian Ocean seabed where the Inmarsat signals indicate it should have.

I would suggest that at this point the search should have been considered completed.

Nevertheless, the “First Principles Review” states on page 15 that the experts’ renewed analysis of the 777 autopilot dynamics indicates that the plane could have crossed the 7th arc “up to 33°S in latitude along the 7th arc.”

Then in the Conclusions section on page 23 the authors describe “a remaining area of high probability between latitudes 32.5°S and 36°S along the 7th arc,” while the accompanying illustration depicts a northern limit at 32.25 degrees south.

In other words, without any explanation, the northern limit of the aircraft’s possible impact point has moved from 34 degrees south in the Bayesian Methods paper in early 2016 to 33 degrees south on page 15 in the “First Principles Review” released at the end of the year. Then eight pages later within the same report the northern limit has moved, again without explanation, a half a degree further north. And half a page later it has moved a quarter of a degree further still.

Is the ATSB sincere in moving the northern limit in this way? If so, I wonder why they did not further search out this area when they had the chance, instead of continuing to scan an area that they apparently had already concluded the plane could not plausibly have reached.

I should point out at this point that the area between 34 south and 35.5 south has been scanned to a total widtch of 37 nautical miles, and the area between 32.5 and 34 has been searched to a total width 23 nautical miles. Thus even if the ATSB’s new northern limits are correct, they still should have found the plane.

As a result of the above I would suggest that:

a) Even though most recent report describes “the need to search an additional area representing approximately 25,000 km²,” the conduct of the ATSB’s search does not suggest that they earnestly believe that the plane could lie in this area. If they did, they could have searched out the highest-probability portions of this area with the time and resources at their disposal. Indeed, they could be searching it right now, as I write this. Obviously they are not.

b) The ATSB knew, in issuing the report, that Malaysia and China would not agree to search the newly suggested area, because it fails to meet the agreed-upon criteria for an extension (“credible new information… that can be used to identify the specific location of the aircraft”). Thus mooting this area would allow them to claim that there remained areas of significant probability that they had been forced to leave unsearched. This, in effect, would allow them to claim that their analysis had been correct but that they had fallen victim to bad luck.

c) The ATSB’s sophisticated mathematical analysis of the Inmarsat data, combined with debris drift analysis and other factors, allowed them to define an area of the southern Indian Ocean in which the plane could plausibly have come to rest. A long, exhaustive and expensive search has determined that it is not there.

d) The ATSB did not fall victim to bad luck. On the contrary, they have demonstrated with great robustness that the Inmarsat data is not compatible with the physical facts of the case.

e) Something is wrong with the Inmarsat data.