A320: 500fpm in DES mode
It is plainly stated in the FCTM that the A320 will do 1000fpm rate if descent, if in managed DES mode, and below profile, until it catches up with the profile.
However, I've observed that below 10000ft, while still in DES mode, the aircraft now does 500fpm! I can't seem to find any reference in any manuals to explain this behaviour.
Any ideas?