Originally Posted by
4Greens
Tried to get my message across on this forum but my thread disappeared. For a start I would like to see all Flight recorder data passed to the ground in real time. This would provide a good start to any analysis. It would also have told us where the first Malaysia loss had vanished.
Originally Posted by Foxcotte
I work for a little operator - and I mean REALLY little - and even us little guys saw the sense and could afford to install a satellite tracker into our aircraft which relays real-time data back to operations throughout each and every flight.
Need to be careful to differentiate between sending real time
location data and real time "flight recorder data" - there are a few orders of magnitude difference in bandwidth and hence cost.
Off top of head / back of envelope:
For Foxcotte's example, it looks like 5 or 6 parameters (presuming location as well), be generous and say 16bits each, and every second (probably they are actually only sent every 10s or maybe 1min ?). That makes maybe 80bits/sec or 0.08kbps max.
For flight recorder on a modern large jet we are talking over 1000 parameters, lets say average 8bits (some may be 12 or 16, but some may be 1 or 2 (on/off or on/off/invalid). Sampling is at least every second but soon going up to 8 per second minimum I think. So that is 1000*8*8 = 64kbps (roughly). CVR is at least 4 audio channels probably at least 16kbps - don't want to run it through low bandwidth voice codecs as there are often non-voice sounds that are of interest - so that is another 64kbps, 128 in total.
128 / 0.08 = roughly 1500 times as much data - and hence 1500 times the cost. A satcom phone call is about 2.4kbps and maybe $1 / min, so that's $50 / flight-minute. Even if I'm out by a factor of 10, that is a significant cost.