Interesting USA Today article on the aircraft's avionics. It states that it was equipped with a TAWS, which should have warned the pilot about ground proximity, and helped him avoid the trap of rising ground on the approach..
Device spurs questions in Polish crash - USATODAY.com
A few quotes of interest:
If the safety device was working properly, it would be the first such crash of an aircraft equipped with the system since its introduction in the late 1990s.
"I really would like to know what was going on in that flight deck because no matter what kind of pressure other pilots have been under or what kind of weather they encountered, no pilot has ignored a TAWS warning. What is so different about this plane that it would break that chain?" Cox said.
Bill Voss, president of the non-profit Flight Safety Foundation, said that the crash may highlight a weakness in the TAWS. Maps of the U.S. and other developed nations are highly accurate, but gaps exist in the maps for countries such as Russia and in the developing world, Voss said.