Originally Posted by galaxy flyer
The FMS knows the landing elevation and all the needed approach altitudes, when an approach is loaded. It wouldn't be hard to inhibit FLC when within some altitude above the FAF altitude or field elevation. Say, 3,000' above the field or 1,000' above the FAF crossing altitude, FLC inhibits an altitude selection below those.
Then after this is "perfected", people will be back at it attempting to use FLCH for approaches - because of inbuilt "protection" the system now offers. When such protection fails, it'll be rinse repeat, "I thought it wouldn't let me do that" all over again.
Here's a couple of alternative ideas: don't use FLCH for approach, don't enter in stupid values, manually control the throttles. They all require paying attention and not letting a computer make all the choices for you.