Originally Posted by Underfire
Do you really think that GPWS has no forward looking capability, or has computations for anticipation? If it warns only for under the aircraft, how is that a warning? (it would be an IS)
You do not understand how GPWS works. It does
not scan forward in any way. It simply uses the RAD ALT, which is a very narrow beam pointing straight down, to work out descent rates and then provide it's various warnings. That is why sometimes with up-sloping terrain you'll get a "sink rate" warning when you are quite within the norms of descent rate and angle (possibly what happened here at Birmingham).
As MotCap has alluded to,
Enhanced GPWS uses a GPS-based terrain database to predict a dangerous approach to terrain and provide warnings eg "CAUTION TERRAIN, CAUTION TERRAIN". From my understaning of the system, it would not have warned this crew because they were too close to the nominal approach path to trigger anything.
Originally Posted by Lonewolf
Sorry, that's going backwards and ignores fifty years of great advances in both avionics and equipment. (And for that matter, regulation and the increase in radar coverage throughout the CONUS).
True, to a certain extent. However, in this case, if the A300 wasn't fitted with a GPS-based FMS, I think it unlikely that the crew would be allowed to do a VNAV descent, and as previously mentioned, it appears that because of the terrain at Birmingham short of 18, an "official" vertical path isn't possible anyway and so would not be published/in the database (hence no GS). So practically speaking, despite all the wizardry around now, not much of it could used to make the approach as safe as many others. Throw in the Dive and Drive concept and you have a good melting pot of trouble brewing...