ok. I think "Hercules" is the wrong image. I need "Ursa". My mistake.
For Arub newcomers:
"Hercules" is not the name for a Build of image. It is the name for the AP-family.
Hercules = IAP-314/314 and IAP-324/325
Ursa = IAP-304/305 and AP-365/367 and AP-303H
If you have only one type of AP in your cluster, you see in "Maintenance/Firmware" only one Image file with a "name". If you have different APs, you see for each type an image File.