Ken Ward wrote:
I hear that there's a DOS application from Filser which resets the
security code, and that this is an issue for a number of secure flight
recorders.

If such a DOS program is being provided to those who are not factory
authorized agents, I would like to hear about it. This would be a
definite violation of the terms under which the unit is approved. If
the case is opened, or the security seal is otherwise broken, the unit
*must* go back to the factory or a designated agent for resealing. The
internal hardware *must* be inspected for possible tampering. Any other
approach would make it trivially easy to subvert the entire system.

That is, there are other units which have a small battery
that when removed for replacement, cause the same problem. How do other
manufacturers handle this?

The usual approach to allow replacement of the lithium cell, is to apply
external power during the replacement. To my knowledge, only the
GPS-NAV allows for replacement of the cell, without opening the case
(and without unsealing the unit). For all other approved flight
recorders using lithium cell (some use long lived rechargeable cells),
when it dies, the seal is lost, and it's time for a trip to the factory.

Marc