[Peetwo]

Mick
15 hours ago

@David  David,  I can't recall exactly where I read that; it's either in the ATSB Bayesian analysis paper or in one of Michael Exner's papers, probably Comments and Questions re ATSB Report on MH370 released 3 December 2015 or in one of Duncan Steel's papers, possibly Background Information on the Pinging of MH370 by Inmarsat-3F1. 

When I get a chance I'll go back over the various papers and see if I can pinpoint it. 
I hasten to add that "It is possible that the anomalous BFO for the last handshake was caused by the airplane changing heading, descending and at an increasing speed" is my interpretation not one I've read elsewhere. 


David
1 hour ago

@Mick Hello Mick. In the Definition of Search Area and Bayesian Methods Reports I cannot find any statement that the last handshake's BFO "shows a significantly higher airplane speed". Nor can I find where an aircraft being stationary "is not consistent with the BFO."  

What I can find is what I have earlier understood to be the case. The Bayesian Report (p7) says that the BFOs at the time in question (and one other) are "deemed unreliable at these times and cannot be used." The cause is that the messages concerned "occurred during transient phases of SATCOM equipment so cannot be used".

That Report (p26) describes how aircraft software compensates for Doppler shift, the residual Doppler data stemming from the aircraft assuming that the satellite is fixed relative to earth, which it isn't.
 
However the Report does add that the aircraft does not compensate for any vertical component of aircraft velocity. So if you reject the above explanation as to why these BFO data cannot be used, you could conjecture a spiral descent might be the source of corruption, though that would account for just one of the two BFO anomalies. Even if you did this would not cover why a stationary aircraft would cause a problem.. 

Maybe I have missed something in which case I hope you will put me right; but if not I do not agree that the final BFO rules out a powered ditching leading to a stationary aircraft. Quite probably something does, but as currently it stands, not that.

Cont/-

David

18 hours ago



@Mick All I have found is a statement from Exner of 5th December (Duncan Steel archives 2069), "Why dismiss the potentially important 00:19:29 and 00:19:37 BFO data as unreliable, given that it is consistent with all the other observations and conclusions related to the end-of-flight analysis? These observations are consistent with the probable aircraft status, simulator results and historical accident data in particular. So why not include these observations in the overall end-of-flight analysis?"


Clearly he thinks that the final BFO data can be related to end of flight data but does not say how where this has been done. 


Para 3 of my post badly worded, though of little consequence.

David continued today...

David
3 hours ago



@Mick Mick, Andrew and Brendan if still there. This unlikely hypothetical of a powered ditching to me remains possible so far, unless the combination of sea state, aircraft strength and APU inlet clearance would have put it outside reason. But the sea state if known is unpublished as is aircraft resilience on ditching and shortly after; and also the pilot's ditching skill.
 

What I surmised before was that the aircraft, ditched under power, would be in the search area. But really all that seems sure is that it would have been on the 7th arc, adjusted a few miles to the NW for the altitude difference.


Where it was on the adjusted seventh arc depends on what happened after the last "fix", the sixth arc, for which there is BFO information. Supposing after that it continued until a pilot elected descent, it then would depend on his descent speed and 'average' track combination as to where on the arc the aircraft would have ditched. If in descent the pilot maintained the previous course, the overall track to ditching still would include course alteration of unknown length for ditching. There could be a spread of possibilities of courses and speeds, compatible with ditching on the arc (and at 00:17:30), possibly constrained by the fuel saving in descent being enough.


However, adding to the above, as you know the sixth arc handshake was only 6 1/2 minutes before 00:17:30 and surely the descent would take longer than that. So if the sixth arc BFO is incompatible with what could be expected from an aircraft already in descent (horizontal speed, vertical speed) that sensibly would rule out a powered ditching.


I hope you will bear with me in what might appear to be a pedantic exercise. With a powered ditching not as yet bowled out, by such as the 6th handshake data, I feel obliged to bring to the ATSB's attention that modelling could show a ditched aircraft might be further away than a few miles from where they have supposed.

Any comments please?  



Brendan
45 minutes ago



@David @Mick  David, if the 6th point has to be the same as now assumed i.e. cruising at altitude, then it puts limits on what could happen in 6 minutes. But if the aircraft can be already well into a descent by then, it could open up more possibilities. Probably would start by seeing what situations the BFO data would be compatible with. If that allows flexibility It might still be possible to come up with a useful prediction given that the flight must end somewhere on the 7th arc which might rule out any diversions. Also bearing in mind that the allowance for a spiral would not apply; the final point would be right on the arc (the plane wasn't going anywhere). But maybe getting too far ahead....

MTF...P2