Mad (Flt) Scientist and Lightning Mate,
The FDR data file shows that the radalt and the pressure agree very well while the plane is flying at 310 knots at 2500 feet. This was shown by adding the radalt to the ground elevation at each position report and using the known local baro and temp to calculate true altitude. As the plane descends and picks up speed the two diverge, with the pressure indicating a higher altitude than the radalt. The difference between them was about 120 feet at the end of the file. This is quite a big discrepancy.
Some pilots have been telling me that the altimeter is more accurate than radalt. I am looking for Boeing's data to refute them.