Flight Data Recorders

"Peter Clark" wrote in message
...
On Mon, 8 Sep 2008 13:08:56 +0000 (UTC), David Lesher
wrote:

Michael Henry writes:

MAK adds that the quality of the flight-data recorder information
is "unsatisfactory" because of partial thermal damage to its
magnetic tape, caused by the intense fire which followed the crash.

Which made me think: magnetic tape?! Surely we've come far enough that
we can be using solid-state storage in flight data recorders?

Does anyone know why FDRs would still be using what, to me, is archaic
technology?

Co$t is why. And while flash-based systems may offer more survivable
recording; consider the recent Qantas incident, where the
depressurization itself was overwritten by subsequent flight.

They could put in a bigger chip for longer recording. I thought most
DRs were only about 1/2 hr looping?

The original CVRs were 1/2 hour looping, carying three channels (or tracks)
of audio, and would erase the tape when the parking brake was applied at the
destination gate. Part of that was due to a combination of technical
necessity and convenience, and part was the dfproduct of negotiation between
the interested parties. The reusult was robust, in the sense that the
recovery of data did not depent upon any part of the equipment remaining
operable I am not familiar with the newer equipment; but would expect
that it would have been made functionally similar--with the possible
addition of more channels of audio.

The original FDRs contained a single use role of stainless steel foil, which
was marked by stylii. The result was *extremely* robust, but even the
second generation of such recorders had a very limited number of data
channels and required frequent depot level maintenance to replace the foil
rolls. Solid state memory simply does not have similar survivability and
there is virtually no change that it will within the next 25 years.
Therefore, solid state memory, in the event that it is actually in use, is
simply a way to obtain more channels of data at less monetary cost in those
cases where the data can still be recovered.

So long as the purpose of the data is to detect failures which can then be
resonably predicted, then it is probably a good trade.