Flight Data Recorders

David Lesher wrote:
... 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.

I can see how solid state storage is more expensive than tape, but I
would have thought that by the time you go through the whole
certification process the cost of the actual medium is just a small
fraction of the total cost... and if the solid state medium offers any
benefits over tape than that small extra cost would certainly be
justifiable.

The other issue you raise really surprises me: the small amount of
flight time for which recordings are kept. Some other posts have
mentioned half-an-hour loop! Does anyone know what volume of data this
entails?

Regards,

Michael


P.S. A quick mental calculation: I can go to Officeworks (in Australia)
and buy a 16 Gb memory stick for AU$100. OK, it's not going to meet the
same fault-tolerance and quality standards, but let's ignore that for
now For those of us in the iPod generation 16 Gb equates to around
300 hours of MP3 music. Obviously you would encode speech differently
and fit a lot more than that, but let's not worry about that. Of course
you also want to record other parameters (temperatures, pressures,
position of controls, etc). I'm just pulling numbers out of the air but
let's say you want to record 1,000 different parameters each sampled 10
times a second. Furthermore let's say the data for each parameter is
stored as a 32-bit value, which comes out to 40kb of data per second or
just under 150 Mb per hour. That's over 100 hours of parameters in our
16 Gb memory stick. Recording voice and data at the same time and I
figure you can fit about 80 flight hours in a $100 USB stick. Not bad
I'm obviously missing out on some important bits but it has made me
wonder: what would be the market for a really small, light, and cheap
uncertified flight data recorder...