Chapter 1 What’s New for FortiOS 5.2.1 : Wireless Networking : 802.11ac and DARRP Support
  
802.11ac and DARRP Support
802.11ac support has been added for FortiOS 5.2, allowing a FortiGate unit to manage FortiAP models 221C and 320C. Distributed Automatic Radio Resource Provisioning (DARRP) is also supported for 802.11ac radio.
Syntax
config wireless-controller wtp-profile
edit {fap221c | fap320c}
config radio-2
set darrp enable
end
end
end