@ Noske
BEA spent a whole month on unsuccessful attemps to read the memory cards and then gave up. From the report: "They were examined at Honeywell, manufacturer of the recorders, in the United States on 5 and 6 January 2009 in the context of an International Commission of Inquiry. Some short-circuits were discovered on the cards. Eliminating the short-circuits allowed a complete read-out of the data."
Thanks for that.
Interesting that the BEA had problems with memory cards and Honeywell found shorts on the board. Sounds like it could have been shock vibration damage to the die connection wires rather than water ingress.
The recovered memory unit housing we see from yesterday's recovery looks in remarkably good shape to me - the indent does not seem to extend beyond the weld seam, and although there is a bit of rust, the seam appears to be intact. If the seal is compromised, then the integrated memory circuit packages will eventually get exposed to 400atmos pressure, and it's possible that the void inside the chip package will collapse onto the micro circuit die. In the past, Aerospace or Mil parts have used ceramic packaging for integrated circuits, with plastic, which is a lot cheaper to fabricate, the norm for commercial applications. There has been some use of plastic in mil aerospace apps in recent years, but one of the problems with plastic packages is that they are porous and allow water to penetrate the void. So, for either package, the void could collapse and crack the die. Or, on the other hand, a plastic package could be subject to a slow increase in pressure gradient (leak through a micro crack in the cylindrical metal containment housing), and it could fill with water and expose the die to corrosion. There are a few manufacturers around who will put die into ceramic packages, but not that many, and usually the cost is hugely expensive compared with plastic. If there is any moisture present around the die, then any application of voltage will cause an electrolyses effect and irreversible damage. So, If there is any suspicion that water has penetrated, the most like course of action is for a trip back to the manufacturer for the top of the package to be removed under controlled conditions and a session of drying and cleaning of corrosive deposits in the hope that maybe something useful can be recovered. Of course, It's quite possible that the CVR/FDR manufacturer has either obtained a special package for the FLASH ram, or has encapsulated the devices in some form of epoxy resin to cover the contingency of water ingress.
It's also interesting that the BEA allowed Honeywell to dig into the electronics. In section 2.4.1 of the EUROCAE document: MINIMUM OPERATIONAL PERFORMANCE SPECIFICATION FOR CRASH PROTECTED AIRBORNE RECORDER SYSTEMS, it states:
NOTE 1: Microscopic examination of the surface characteristics of memory
devices is not acceptable as means of data recovery.
NOTE 2: The repair of individual memory devices is not permitted.......
Seems a rather restrictive policy considering that all measures need to be applied to discover the truth - maybe it's a legal issue...
On a more hopeful note, we know from the interim report that the G forces experienced for the majority of passengers (front to rear of aircraft) was in the range 100 to 200G (from pathology), so it is therefore reasonable to say that the FDR and CVR experience something similar or less, and was then subjected to 400atmos pressure for 2 years. Given that these devices must pass certification at 3400 G (6.5ms) and also be able to resist 600 atmos (up to 30 days to pass certification test), I think it reasonable to assume that the contents have survived even after all this time. However, I'm not so confident about the FADEC's and the other 12 or 13 subsystems with non-volitile memory devices which would have minimal, if at all, protection from pressure.