Question:Categorize software level
 

The EGPWS function is significant system for aircraft and needs to applicable database for terrain. Software level is described in DO-178C as level A thru E.
How about the terrain database for EGPWS? Level C or D? I think not A, B and E.

TSO C151d defines unannunciated failure, false terrain warnings, and presentation of misleading data as major failure conditions. This sets the system design assurance level as at least level C. It depends on the system design, but most likely the software, including the terrain data, would need to be level C.