We often get a question "what are the differences between the AV GDU 1040, 1040A and 1044B?". Here you can find an answer to this question.
All variants work in the same way and the only difference is in the autopilot buttons/knobs on the left hand bezel.
Below you can find the description of each variant.
AV GDU 1044B
This is one of the more popular variants and it includes all of the autopilot controls including knobs for the HDG, ALT and CRS as well as buttons for the AP, FD, HDG, ALT, NAV, VNV, APR, BC, VS, FLC, NOSE UP and NOSE DN.
AV GDU 1040
This variant is similar to the 1044B with an exception that it doesn't have the autopilot buttons but it does have the knobs for HDG, ALT and CRS.
It's quite popular to use a setup where the PFD is 1040 and MFD is 1044B. This way both pilot and co-pilot have access to autopilot knobs on their respective G1000 and the autopilot buttons are easily accessible by both pilots as they are on the left side of the MFD and therefore in the centre of the cockpit.
AV GDU 1040A
This variant comes with no autopilot controls whatsoever. It's commonly used in more complex aircrafts where we have a separate autopilot controller like the GMA 710 located in the top centre of the instruments panel.