EGPWS - Required Nav performance for certification?

[superfrozo]

Gents, quick question:

Does anyone know whether there is a minimum nav suite requirement to enable certification for EGPWS operation? Specifically, how much positional accurracy is required to validate the Digital Terrain Elevation Data?

Ie. Is a specific combination of INS & embedded GPS ?
...triple INS with DME/DME/DME updtating?
...or is it merely a maximum demonstrated drift rate combined with a required kit update rate???

I have done tech quiz searches with nothing specific addressing this topic, any info would be greatly appreciated.

Thanks in advance!

[Daysleeper]

In the UK AFAIK the CAA will not approve any TAWS system that does not have sat nav independent of the aircraft systems.

[superfrozo]

Thanks for the reply Daysleeper - I imagine that means that the JAR/FAA rules also require a GNSS input to kit position.

Interesting that much emphasis is placed on the (seemingly) infallible GPS position. I have personally seen some weird & wonderful erroneous GPS positions.