Is the epson workforce 520 an airprint printer?

This should help

http://support.apple.com/kb/HT4356

I don't see your printer on the list but please doublecheck me, I've missed htem before. If your printer isn't on the list then it can't airprint. You'll need to look for apps from Epson if they have any or look to third party printer apps like print n share, print central or printopia (there are plenty more too) and use them.

No it isn't. You can look to see if Epson has any apps in the App Store or try a 3rd party application like Print Central.