What is the consequence of changing from Mode 2a envelop to the Mode 2b envelop? I don't have that information in our Aircraft Manual (Volume One).
This is what I found (without downloading the Honeywell manual):
•Mode 2B provides a desensitized alerting envelope to permit normal landing approach maneuvers close to terrain without unwanted alerts. Mode 2B is automatically selected with flaps in the landing configuration (landing flaps or flap over-ride selected) or when making an ILS approach with Glideslope and Localizer deviation less than 2 dots. It is also active during the first 60 seconds after takeoff.
By the way, the below is from the normal landing section in our Boeing manual:
• For FLAPS 15 landing,• GROUND PROXIMITY FLAP INHIBIT switch - FLAP INHIBIT