The ULB is a standalone item. It is attached physically to the CVR/DFDR by a double 'u' clamp arrangment. It has been known to get separated from the recorder, sometimes under strange circumstances. The most recent was a Yemenia Airways A310 that went down on its approach to Moroni Airport in the Comoros Islands - 30 June 2009. There was one recovered survivor (others survived the crash but drowned), and IIRC the a/c was stalled making a turn during the approach.
The data recorders are contained within the Crash Survivable Memory Unit (CSMU), and are expected survive a 3400g + impact, 1,100 degree Celsius fire for 1 hour, a 227kg steel ball with 6.3mm protruding pin drop test from height of 3m, 5000 psi dry pressure test on each side for 6 minutes, a similar water tank pressure test for 24 hours, and salt-water immersion for 30 days. These are the "minimums".
All electrical contact with the CSMU is severed when the acceleration on a multi-axis switch exceeds 2.5g. The non volitile memory can usually be recovered by the manufacturers even after some or all of the design conditions have been exceeded. The Nixon tapes didn't quite meet these standards!
Last edited by mm43; 14th Feb 2011 at 21:22.