JD-EE
The following was in a post I made to a different thread sometime ago:-
If AF447 had been sending its position via SATCOM every minute instead of the 10 min interval initiated by AF Operations/Maintenance, the search area would have been reduced to a maximum of 8NM radius. That's assuming it crashed in the 59th second, which gives an area of 201 square NM (690km^2). We do know that it was still airborne 4 minutes later, and the BEA are using 0215z as their crash time. This represents the 8 x 5 = 40NM radius they are ostensibly confining their search to, i.e 5026 sq. nautical miles (17,240km^2).
This boils down to one simple fact, i.e. the search area increases by the square of the time between position reports.
Just phoning home at smaller intervals increases the SATCOM costs proportionately, but reduces a search area by the square root of the changed interval. The costs of one versus the other are too large to even contemplate.
In meantime, implementing the above is the cheapest thing that AF or any other carrier operating Oceanic routes outside of SSR coverage could do right now.
I wouldn't get too concerned with the order of accuracy of any given position. There is a reason for that, e.g. an a/c over the equator reports with an accuracy of 0.01° or +/- 555.6 meters (1,824ft) in both the Lat and Long coordinates, and progression towards either pole increases the accuracy of the Longitude to say at 30°N by 1/secant 30° = 555.6*0.866 or to +/- 481 meters, and at 60°N to +/- 278 meters. The Latitude accuracy essentially remains the same - small changes on account of the oblate spheroid shape being ignored.
The BEA Flight Data Recovery Working Group Report -
http://www.bea.aero/en/enquetes/flig...nal.report.pd has already indicated that "Regular transmission of basic aircraft parameters (via ACARS for example)" is the third preferred item on its "to do" list. As
CJ has indicated, a few bytes saved here or there is not really the issue, and progressive Deltas might come unstuck when things get sticky. I expect that any consensus on common flight data parameters to be sent regularly by ACARS is still a long way off.
mm43