Originally Posted by
gulliBell
And finally, the EGPWS. I'm a complete novice on this system, but from the little I understand, the "low altitude" function was enabled which significantly reduces boundary warnings. However, mode 6 was still available to them which enables an "ALTITUDE ALTITUDE" callout. And that's exactly what they got 27 seconds before impact, and again at 2 seconds before impact. My reading of it the EGPWS was doing exactly what it was programmed to do, despite the terrain data issue which has been highlighted. The comments column in the CVR transcript attributes this warning to the radalt. As I mentioned a few pages earlier, I've never seen a radalt associated with an ALTITUDE warning, I doubt very much that the radalt initiated this warning in this instance, it was the EGPWS issuing the warning exactly as it was designed to do for the mode it was commanded to be in. An ALTITUDE ALTITUDE warning from a EGPWS must be responded to by crew avoiding action as set out in SOP. But as I said, I'm a novice on this aspect.
So much for me taking the time to give the
exact aural alerts (post #1008, which you acknowledged in #1028).
Maybe I should have answered what you asked then: "Yes, it is the behaviour of the S92!"
Mode 6 is a
'non-database' mode of the EGPWS, which uses RADALT height as the primary input. I refer to post #1008 for its calls.
The EGPWS look ahead alerting mode (which uses the database) gives "CAUTION TERRAIN", or "WARNING TERRAIN" calls, depending on the 'time to impact' calculated.
The comments column in the CVR transcript is correct.
Only 1600 hours on S92, what do I know?