Machinbird;
Good post on "speculation" etc. I think it is entirely reasonable to use available information to form theories from knowledge and experience, but the basis for theory must be there for all to see and where disagreement arises, the facts must be available to demonstrate same.
The BEA 2nd Interim Report states that AF447 had a Honeywell SSFDR 980-4700-42. Information on this recorder may be easily found on the web using standard search techniques. It may help with a few details. The link can't be posted because it is commercial material. The SSFDR weighs about 13 lbs and is mounted between frames 84 & 85 very close to the bottom of the airframe.
mm43;
I've puzzled about how the CSMU/ULB departed, and the only explanation I can come up with is:-
The 'g' forces at impact were complex, and the initial underside impact caused the the whole SSFDR to be punched up, and at the same time the mass of the CSMU tried to continue forward and to port, resulting in the securing bolts pulling then shearing off.
Perhaps a further look at the V/S clevis joints damage may help explain it.
That doesn't give a satisfactory explanation as to why the CSMU/ULB left its mount before the SSFDR, unless the tensile strength of the CSMU bolts were less than those of the SSFDR securing bolts.
I think that is a very reasonable description. I think the broken CSMU should not a complete surprise in the circumstances of the impact on a relatively light section of the structure. Loss of the CSMU has occurred once before as has been posted, and been found again so we can expect that it is a matter of time. There will be opportunity in the future to discuss designs and why the separation, (something Honeywell is likely talking about now), but at the moment finding the CSMU is primary, and then reading it.
It may be bolt tensile strength was exceeded or that the bolt-heads may have pulled through the bottom of the casing. Either way, a clear dimpling of the bottom surface can be seen where the bolts were and the casing itself has been stressed sufficiently to bend upwards in a same way that mirrors many other recovered parts in accordance with the impact described in the BEA Interim Reports.
The first place I would be looking would be the tail section and where the tail section lay. The area above the recorder is relatively clear and the pressure bulkhead is just forward and the heavy HS wing box, THS equipment, rudder control equipment and of course the APU, aft of the HS box. The CSMU may very well have shot upwards in the instant of impact into the collapsing framework from below and above.
Anyway, as you say, it's all reasonable speculation but I don't think they're reading here for advice. I look forward to news of finding the CSMU.