Download iPadOS 5.1.1 (9B206) for iPad 1

You will have to note that you can only restore signed IPSW firmware files using iTunes or 3utools.

✅ This IPSW firmware is Signed

Firmware Identifier iPad1,1
iPadOS Version 5.1.1
Release Date 1970-01-01
Update Date 2012-04-27
Sha1sum
ad9b607439250f2337fe132890dadc4c487beca8
Sha256sum
3ced89736d6149c92d59484648e1fffcc61debeeb88e0e528dca9b288707fa18
md5sum
859a6ded3129af1ed0d56f3e25c873a2
Size 0.71 GB
FileName
iPad1,1_5.1.1_9B206_Restore.ipsw
Status

Download IPSW (0.71GB) Check device info
Release Notes

It should be noted that these are the official release notes for the from Apple

This update contains improvements and bug fixes, including:

For information on the security content of this update, please visit this website:

http://support.apple.com/kb/HT1222