By default direct management for FortiGate managed FortiAP’s is disabled. You need to enable this if you want to set a static IP address.

Enabling AP Management

• Navigate to WiFi & Switch Controller –> FortiAP Profiles
• Edit the profile your AP’s are assigned too

First the password!
Before enabling direct management, set a reasonable password.

• AP Login Password: Set
• Enter the password you want to use for the APs and click OK

Next set the protocols you wan to allow

• Administrative Access: Enable HTTPS and SSH (I would not recommend enabling telnet or http since they are insecure)
• Click OK

That’s it, you can now browse to the AP at it’s IP address using HTTPS and login using admin for the username and the password you set above.

Setting a Static IP Address

• Browse to the AP’s IP address using HTTPS and login using admin for the username and the password you set for managment.
• Change the Address Mode to Static
• Set valid IP information for your AP
• In the WTP Configuration section set AC Discovery Type to Static and set AC IP Address 1 to the IP address of the FortiGate AP interface

That’s it!