Earlier today, the Australian Transport Safety Board released a document entitled “MH370 — Search and debris examination update.” Perhaps occasioned by the recent completion of the towfish scan of the Indian Ocean seabed search area, the document updates earlier ATSB reports and offers some intriguing insights into what may have happened to the plane. Some thoughts:

— The first section of the report expands upon an assertion that the ATSB made in an earlier report: that the BFO values recorded at 0:19 indicate that the plane was in an increasingly steep dive. Indeed, the newly published calculations indicate that the plane was in an even steeper dive than previously reckoned: between 3,800 and 14,600 feet per minute at 00:19:29, and between 14,200 and 25,000 feet per minute at 00:19:37. On the lower end, this represents an acceleration along the vertical axis from 37.5 knots to 144 knots in eight seconds, or 0.7g. On the higher end, this represents an acceleration along the vertical axis from 140 knots to 247 knots, likewise about 0.7g. If the plane were freefalling in a vacuum, its acceleration would be 1.0g; given that the airframe would be experiencing considerable aerodynamic drag, a downward acceleration of 0.7 would have to represent a near-vertical plunge, which a plane would experience near the end of a highly developed spiral dive.

— The second section describes end-of-flight simulations carried out in a Boeing flight simulator in April of this year. These tests were more detailed than others carried out previously. Evidently, modeled aircraft were allowed to run out of fuel under various configurations of speed, altitude, and so forth, and their subsequent behavior observed. Thus, the exercise modeled what might have happened in a “ghost ship” scenario. Notably, it was found to be possible for the plane to spontaneously enter the kind of extremely steep dive described in the previous section. This being the case, the report states, the plane “generally impacted the water within 15 NM of the arc.” This is not surprising, considering that the plane had already lost altitude and was plummeting straight downward. This offers a tight constraint on where the plane could plausibly be if the 0:19 BFO analysis is correct.

— The third section describes the results of debris drift modeling that has been informed by tests involving replica flaperons “constructed with dimensions and buoyancy approximately equal to that of the recovered flaperon.” An important point not addressed by the report is the fact that the French investigators who tested the buoyancy of the flaperon were unable to reconcile its observed behavior with the observed distribution of the Lepas anatifera barnacles found growing on it. So when the French ran their own drift models, they had to run them twice, one for each buoyancy condition. Apparently the Australians overcame this paradox by discarding one of the states.

— The third section notes that, according to modeling carried out by the CSIRO, debris which entered the ocean in the southern half of the current search area would not likely reach Réunion by the time the flaperon was recovered. Meanwhile, debris that entered the water significantly north of the current search area would reach the shores of Africa much earlier than the time frame in which pieces were actually discovered there. Using this logic, the report concludes that the northern part of the current search area is probably correct. However, this seems dubious reasoning to me: one would expect a gap between the time debris arrives in Africa, and the moment when it is discovered. Also, debris can move quickly across the ocean, only to be trapped in a local gyre and move around randomly before beaching. Therefore I think the argument that the pieces couldn’t have originated further north is flawed.

— The fourth section, describing the damage analysis of the flap and flaperon, is the most interesting and newsworthy of all. In short, it makes a persuasive case that the flaperon and the inboard section of the right-hand outboard flap (which, rather remarkably, turn out to have been directly adjacent) were in the neutral, non-deployed state at the moment of impact. Assuming this is correct, this eliminates the IG’s flutter theory, as well as the widely discussed theory that the flap was deployed and therefore indicative of a pilot attempting to gently ditch the plane. Proponents of these theories will continue to argue on their behalf but in my opinion they were dubious to begin with (given the shredded condition of much of the recovered debris) and are now dead men walking.

— No mention was made of Patrick De Deckker’s exciting work with Lepas shells.

— Overall, the thrust of this report is that the plane went down very close to the seventh arc in a manner consistent with a “ghost ship” flight to fuel exhaustion, exactly as the ATSB has assumed all along. There is, however, one very large elephant in the room: the fact that Australia has spent two years and $180 million demonstrating that the plane’s wreckage does not lie where it would if this scenario were correct. Therefore it is not correct. The ATSB’s response to this conundrum is rather schizophrenic. On the one hand, it has recently floated the idea of raising another $30 million to search further—presumably the small remaining area where a plane just might conceivably have come to rest in a ghost-ship scenario, as I described in an earlier post. On the other, it has today convened a “First Principles Review” consisting of experts and advisors from Australia and around to world to scrap their previous assumptions and start with a clean sheet of paper. This implies an understanding that they have proven themselves wrong. I wonder how many assumptions they will scrap. Perhaps, as Neil Gordon mused in his interview with me, that the plane wasn’t really traveling south at 18:40? Or perhaps they’ll dare to go even deeper, and contemplate the provenance of the BFO data… ?

— A postscript: Richard Cole recently posted an update of the seabed search (below). I’m intrigued by the fact that the Fugro Equator has deployed its AUV near the northern end of the search zone. When I interviewed him for my last blog post, Fugro’s Rob Luijnenburg told me that the northern end of the search zone was flat enough that it could be scanned by the towfish alone; there was no need for an AUV scan to infill the craggy bits. So why is the AUV looking there now? Especially given that it’s very close to an area just reinspected by Dong Hai Jiu 101’s ROV. Another MH370 mystery.

UPDATE 11-2-16: I emailed Rob Luijnenburg and he immediately responded: “The AUV is scanning in a section in the north part of the priority search area in the very rugged terrain south of Broken Ridge (the east -west mountain range at approximately the 33rd parallel)… Generally the AUV is deployed in spots of extremely rugged seabed to complete the 120,000 sq km priority area survey.” Worth noting is that if the search gets expanded northeastward, it’s going to be into very rough terrain indeed.