The ICAO report analysis shows that routes can be generated from the start point to the final ping arc at a variety of speeds that are not impossible. Once a start point and a speed are selected there is only one choice for the Southern route (at least a route that has a chance of being close to the BFO data). I get speed changes of between 6 and 16degrees/hour for the first four route segments (a fit the red zone) and 1degree/hour for the 22:41-00:11 segment; the path looks roughly consistent with the report maps (figure 1). I get a slightly lower speed (311 against 323kt in the ICAO report) – the report analysis would have used wind corrections, I did not. Anyway, the precise route does not matter, the key issue is the BFO at the final ping arc(s).
Figure 1: Fit to the ICAO report start point and red-zone using a constant speed route of 311kt. To be clear this in not intended to prove the aircraft went to the red zone
Example Fit To The Positions In The ICAO Report Using A Constant Speed Course Of 311kt. Is Not Intended To Show That The Red-zone Is Correct Photo by RichardC10 | Photobucket
Red/yellow/green zones meaning: In the report map the 00:11 markers for speeds 323, 332 and 344 are marked with 30000, 15000 and 3000ft respectively. The ping-arc data is very slightly sensitive to the absolute height and the BFO not at all sensitive, so if heights has been used in these plots it must have used a
change of height in the modelling. Also, if the fuel was exhausted at 00:18, flying at 344kt/3,000ft would not give a longer range than 323kt/30,000ft so these values are not height for the whole route. The rate of climb/descent is part of the overall Doppler due to the aircraft's own motion and is not corrected by the on-board system (as is clear by the change of BFO at 1710UT in the original Inmarsat graph - top of climb). So if the aircraft was descending at 00:11 the BFO value at the final ping arc would have been changed, giving a lower value.
The red-zone track states a final height of 30000ft, so no descent. The required descent rate for the 344kt track at 00:11 (green zone) to bring the BFO value back to that predicted for the 323kt track (red zone) is 230ft/min (4.2Hz in BFO). That would give a change of height of 21000ft in the 1.5hrs between 22:41 and 00:11, so compatible with the difference between the supposed height of 30000ft at 22:41 and the marked 3000ft at 00:11. Presumably work in the simulator has indicated some basis for this.
So in summary, the hypothesis:
a) The final BFO data (which we do not have – we have only the initial set released to the families) is a fit to the Red Zone.
b) The Red, Yellow and Green zones refer to possible rates of descent after 22:41. The red zone is the best match to the (assumed) 00:11 data with the aircraft level at 30000ft. If the aircraft was descending at 230ft/min the green zone would be the best match to the 00:11 data. It is taken here that some work on the aircraft analysis has given a basis for this.
c) This explains why there is no green or yellow zone North of the red zone. The aircraft is not expected to climb from 30000ft, so the BFO cannot be changed to deflect the final position North.
Again, here I am trying to understand the presented analysis, not offering some alternate model.