Running the official YouTube app on iOS 5.1.1 (commonly found on the 1st Generation iPad) is challenging because Apple and Google officially stopped supporting this version years ago. While the app is no longer on the App Store for this OS, there are several methods to get it running or find a usable alternative.
To get YouTube running again, you aren't just looking for an old file; you are looking for a modified experience. The most reliable method involves using or a specific legacy YouTube IPA paired with a custom API key. youtube ipa for ios 511
If you meant something else (e.g., testing your own signed IPA, or questions about app signing and provisioning profiles), tell me which and I’ll give a safe, legal guide. Running the official YouTube app on iOS 5