Short, and worth the two minutes: the sheets are free to use and carry no warranty, and a few of the methods behind them are being pushed outside the range they were validated in.
Using the sheets
Use them. There is no account, no fee, no licence key and no limit on how often. Print them, take them to the workshop, use them for a university assignment, use them for a paid job. Nothing is held back for a paid tier because there is no paid tier.
The figures are yours; the site is not. Take what the sheets give you and use it — in a design, a build, a project report, a thesis, a paid job. Keep the design files, the CSV exports and the airfoil coordinates the site generates for you: those outputs carry no claim of ours. Quote a figure and cite it, and cite the date as well as the revision letter, because these pages are corrected in place.
What is reserved is the material itself: the text, the drawings, the code and the compiled tables. Do not republish the sheets, mirror the site, or fold this into another service as though it were yours. If you want to do something this does not allow, ask — help@saqr.com.qa, and the answer is likely to be yes.
Some of what you see here was never ours to license, and the full notice in the
repository's LICENSE says which. The measured airfoil figures on Sheet 02
belong to the people who made those measurements and are credited on the
sources page. The ten sections the site generates are
published constructions — the NACA ones are United States government work, the
curved plate and the stepped section are plain geometry — so the coordinates it
hands you are computed here and free of any claim. The seventeen it does not generate
stay with their designers, which is why the site points at them rather than reproducing
them.
There is no warranty
The sheets are provided as they are. Every figure is an estimate produced by a published method, and several of those methods are being applied outside the range they were validated in — the drag build-up most obviously, which uses a full-size aircraft method an order of magnitude below the Reynolds numbers it was tested at. Each sheet says so in its own words, at the bottom, and those statements are part of these terms.
Soft figures are labelled. Where a number was compiled from practice rather than measured, the sheet says "compiled, not measured" and means it.
What the sheets are not
- Not an airworthiness determination.
- Not professional engineering advice, and not a substitute for a licensed engineer where one is required.
- Not a substitute for flight testing, for the manufacturer's data on a part you have bought, or for your own judgment about an aircraft you can see and they cannot.
- Not a certification tool, and not intended for anything carrying a person.
What is yours to get right
Flying is regulated where you live and at the field you fly from. Airspace rules, weight limits, registration, remote identification, insurance and club rules are your responsibility and this site does not know any of them. A design these sheets call sensible may still be one you are not permitted to fly.
Build in stages and test in stages. A number on a screen has never yet held a wing on.
Liability
To the fullest extent the law allows, Saqr Consulting accepts no liability for any loss or damage arising from use of these sheets — including a damaged or destroyed aircraft, damaged property, or a design that turns out not to work. You use them at your own risk.
Nothing here excludes liability that cannot lawfully be excluded.
The sheets change
Every sheet carries a revision letter, and it moves when the numbers behind it move. Corrections are applied to the current revision rather than kept as a historical archive, so a figure you noted last month may not be the figure the sheet gives today — and if it changed, it changed because the old one was wrong.
If a correction affects a number you relied on, the changelog in the repository records what moved and why.
Corrections
A correction with a source behind it is the most useful thing you can send, and it goes into the next revision credited. That is the whole quality mechanism, and it only works if people send them. The address is help@saqr.com.qa, and every sheet has a button that opens it.
Governing law
To be confirmed. Saqr Consulting operates from Qatar, so Qatari law is the natural answer, but this line should be settled deliberately rather than assumed — it is the one part of this page that wants a lawyer's five minutes.