1) you can check if any directory is created in flash?
2) check if there is enough space to download and extract the archive?
if not you must erase the existing image before you can download the new version
(this is a critical point, when no image is present)
3) when i search software.cisco.com the image for the 1140 series has the name
c1140-k9w7-tar.153-3.JD17.tar for autonomous
or c1140-k9w8-tar.153-3.JD17.tar for lightweight
so it may be you are loading the wrong image.
Just Checked the ap3g1-k9w7-tar image is for Aironet 3500e Access Point
4) you renamed it to .default,
when the AP reboots with the button pressed for 30 seconds it will look for an image in the tftp server with a specific address and a specific filename depending on AP-model with extension .default
and load it without needing CLI commands. Look at this document section reloading image
f you do not use this default-tftp mechanism, I suggest to keep the original filename, including version for the tar archive when you do a manual tftp download