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Post by jaydeehess on Nov 1, 2006 19:12:52 GMT -4
how does the NTSB get positional data from the DFDR? Here's the pdf of the DFDR report. for AA flt 77 that hit the Pentagon www.ntsb.gov/info/AAL77_fdr.pdfThe NTSB also has an animation of the flight from the time it took off to the last recorded data on the DFDR. However I was wondering what data points on the DFDR would be used to plot the position over the Earth of the plane. It has pressure altitude so the height I can see being derived from that but as far as I can ascertain the only data points recorded that would aid in setting the position of the aircraft would be the acellerometers data. That would make the position no more accurate than the old Inertial Navigation System used before GPS. Anyone??
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Post by gwiz on Nov 3, 2006 5:19:02 GMT -4
Presumably the normal radio-navigation data from systems like VOR and DME.
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Post by jaydeehess on Nov 4, 2006 22:58:40 GMT -4
That's what it is beginning to look like.
What is the error in a VOR reading or a DME distance?
I know one would be a fool to try and automate VOR/DME avionics to get a plane into position to land. It isn't accurate enough, but how far out would it be in determining the location of an aircraft within say 15 miles of the ground station VOR/DME?
100 feet? 200?
Could it account for the NTSB animation of the flight showing the a/c well north of the track over the lampposts?
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Post by Tanalia on Nov 5, 2006 4:58:30 GMT -4
Accuracy of a VOR tends to be around 0.5o, or roughly 50' per mile of distance (so up to about 750' off at 15 miles).
Accuracy of DME is nominally 185 meters, roughly 600'.
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