Sometimes public drafts or presentations summarizing the standard (often titled "VITA 51.1 Overview") are available on engineering sites or within reliability engineering presentations. These are useful for understanding the methodology but are not the final standard.
Think of it as the "Rosetta Stone" for system architects. It creates a standardized naming convention and mapping structure so that when you order a backplane or a plug-in card, you know exactly which pins carry data, which carry power, and which are ground. vita 51.1 pdf
No one can legally share the full VITA 51.1 PDF here due to copyright. However, you can: which carry power
Then compute MTBF = 1/λ