Firmware update Cisco AP 1131 (IOS)

enter Privileged EXEC mode (enable)
format flash: (remove all files on in the flash include startup config)
archive download-sw tftp://x.x.x.x/c11yy-yyy-yyy.yyy-yyy.JA2.tar (x.x.x.x ip address off running tftp server
copy run start
reload