FAR 52.209-4
First Article Approval — Government Testing
What it says
Requires the contractor to deliver first article units for government testing and approval before full production, with delivery schedule and payment tied to first-article approval.
Why it matters on DIBBS
FAT (first article testing) adds months and real cost to an award. New sources on an NSN often face FAT while approved sources are waived — factor it into both price and delivery days.