Triple 7 Drivers...

[skypine69]

In an RJ the EGPWS is tied to the FMS. The airplane has to know where it is in order to display the terrain info. That is why when our older FMS units that dont have GPS get lost the terrain info goes away as well. Happens flying low to the ground (like when getting ready to land, generally the most important time to have terrain info.) I have not needed the terrain info at FL330 for quite a few years now.

 

[Beetle007]

I think I have to make a "clarification" to my previous post. Once again, take everything I say with a grain of salt (low time pilot)....and please inform me if any of my information is incorrect.

FlyChicaga. You said "I'm no expert, but I don't think flying into an airport not in the FMS database will have any effect on the EGPWS functions." You are 100 Percent correct. However, more significantly, you WILL get a warning if the airport is in the FMS database, but not yet entered into the EGPWS database. This is what would throw most pilots off.

In my previous post I mentioned that the FMS and EGPWS databases are seperate. However, I was specifically talking about airport/runway and terrain info. I was not implying that they are independent systems. EGPWS normally get its position information directly from the FMS and other systems. For example, on the A320 the EGPWS gets its position information from FMGC #1, and altitude information from ADIRU #1/captains baro reference.

The difference in the databases is significant, and I will explain why. The EGPWS database, specifically the terrain clearence floor function, normally includes runways (airports) with instrument approaches over a certain length. However, this database must be updated just as any other. Even if the Runway is in your FMS database, it might not yet be included into your EGPWS database. Therefore you would have to turn off the EGPWS portion of GPWS during such an approach or you will get a waring. This might occur at newly built runways etc.

If this is an occurence at an airport that your "airline" flys into, you will most likely have FIF guidance specific to the approach. Most likely telling you to select the TERR push button to OFF when making the approach.

Vice Versa, an airport might be in the EGPWS database and not in the FMS database. Therefore, you would be able to land at an airport not in the FMS database without worrying about any warnings. just as flyChicaga mentioned =)


Cheers,