AF 447 Search to resume

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Metron report

Hi there

The Metron report give all the details about how the posterior distribution maps (posterior to the Phase III, to be used for the Phase IV, see fig 32 & 33 p 35) are estimated. It combines several prior distributions (linked to flight dynamics, the reverse drift analysis, the bathymetry, etc...) with posteriors (the several search phases) to build the Phase III posterior distribution.

I am a bit puzzled by several underlying assumptions:

-the FD (flight dynamics) distribution is built over 9 cases (quite low !) which are not all departing from FL 350, and this FD distribution aggregates cases with very different vertical speeds (from 12 kft/mn to 32 kft/mn): is the relatively good state of the recovered Galley G2 compatible with such high vertical speeds (20, 25, 30 kft/mn) ? are all the 9 cases compatible with the BEA findings about the attitude of the plane when it impacted the surface ("en ligne de vol") ?

-some prior distributions are combined in a fixed 30% versus 70% fashion, with little/subjective explanations:
"The prior distribution before surface search by aircraft and ships is taken to be a mixture of 70% of the FD Prior given in section 3.1 and 30% of the RD Prior given in section 3.2.2." (page 9, FD=Flight Dynamics, RD=Reverse Drift).
"Underwater Search Prior. For the purpose of evaluating the underwater search, we formed a prior which is a mixture of 30% of the Surface Search Posterior in Figure 14 and 70% of the FD Prior in Figure 2." (page 17)

This seems to explain why the final distribution used for Phase IV is mainly located on the LKP (in a small radius < 20 NM).
Jeff