The two documents almost everything comes from
FAA AC 43.13-1B CHG 1, Acceptable Methods, Techniques, and Practices — Aircraft Inspection and Repair. The advisory circular that governs general practice in the United States for work not covered by manufacturer data.
FAA-H-8083-31, Aviation Maintenance Technician Handbook — Airframe, Volume 1. The FAA's own training handbook, which carries the tables and ratios the AC leaves out.
Both are public documents published by the FAA, and every page links to the PDF it drew on. Where a figure comes from somewhere else — a manufacturer's convention, a military standard, a training manual — the page says so in its sources block, by name.
Where the two documents disagree, we say which one says what rather than picking one silently. There is a worked case on the edge distance calculator: the 2D minimum is the AC's, verbatim, while the 4D maximum and the 2.5D countersunk minimum are the Handbook's and appear nowhere in the AC. Most pages on the internet attribute all four to the AC. That is the kind of error this process exists to catch.
What actually happens before a page publishes
1. Every figure is looked up, not recalled. The source documents are queried directly and the relevant sentence is read in full. Nothing goes on a page from memory or from another website.
2. The quote goes on the page. Where a figure is load-bearing, the source's own wording appears in the sources block so you can check it without downloading a 700-page PDF.
3. Derived numbers show their arithmetic. Neither FAA document publishes a dimensions table for AN470 rivets; the Handbook gives ratios instead. So the AN470 page computes the head dimensions from those ratios and says that is what it did, rather than presenting them as measured values.
4. What cannot be sourced is not published. The drill size chart had a pilot-drill column giving #41 and #31. Neither FAA document names them as pilot drills, so the column came out of the sourced table and became a note labelled as shop practice. A shorter table that is right beats a longer one that is partly invented.
What sourcing does not buy you
None of this is approved data. The Structural Repair Manual, the Aircraft Maintenance Manual and the type certificate holder's instructions govern any actual repair. Where they differ from anything here, they win — and we would want to hear about it.
Documents get superseded. AC 43.13-1B dates from 1998 with a 2001 change. Check that the edition you are relying on is current for your work.
Correct in general is not correct for your aircraft. A rule that holds for general sheet metal practice may not hold for a pressurised fuselage, a composite structure, or a specific type.
Tell us when we are wrong
This is the message we most want to get. Point at the page and the figure, and give us the document and paragraph if you have it.
We check it against the primary source, correct it if you are right, and say on the page that it was corrected. Reference content that quietly edits its mistakes is not worth trusting, and a correction nobody can see is not a correction.
Contact details are on the contact page.