Originally Posted by
Mark Six
Gullibell, the aircraft I fly has much the same equipment and avionics as the R116, including the exact same model of EGPWS. Descent below the preset RADALT height (in this case 180') will cause an "Altitude, Altitude" warning from the RADALT. There is no 'Altitude, Altitude" aural alert associated with the EGPWS. Some of the terrain associated alerts are "desensitised" when landing gear is lowered. The crew of R116 selected LOW ALT mode on the EGPWS. I don't know about R116 but in the A/C I fly it is only possible to display either the EGPWS page or the weather radar picture, not both on the same display. If your display is in weather mode and an EGPWS alert is triggered the display will automatically switch from weather to TAWS. Obviously you don't want to suddenly lose your radar picture at a vital stage of a rig approach or when using radar for weather/terrain avoidance so LOW ALT is enabled to reduce the threshold for EGPWS warnings. It seems counter intuitive to desensitise your EGPWS when flying at low altitude but that is often what is called for.
Although as long as TAWS is displayed on a screen it wont 'pop up' and replace your weather radar, this can be done by displaying TAWS in the ARC mode of the PFD, then you have both TAWS and Weather on the screens side by side.