Why the W&B calculator ships with zero aircraft presets
Most weight-and-balance calculators ship with a dropdown of common aircraft. Pick C172. Pick PA-28. Get the numbers pre-filled. We deliberately don't do that. Here's the engineering reason — and what it tells you about the rest of our stack.
The new weight & balance calculatorwent up on the /tools page tonight. It does the moment math, plots your point against your envelope, and tells you whether you're inside it.
The thing it doesn't do — and the thing every other W&B tool on the internet seems to do — is offer a dropdown of common aircraft. No "Cessna 172." No "Piper Cherokee." No "DA-40." You enter every number yourself from your POH.
I want to be honest about why.
Every airplane weighs different
The 1978 C172N at the school down the road and the 2014 C172S two ramps over share a model number and almost nothing else. Different empty weight. Different empty arm. Different installed equipment list. Maybe one has long-range tanks. Maybe the other was re-weighed last month and the moment arm shifted by half an inch.
A "Cessna 172 preset" in a calculator is one of two things. Either it's the manufacturer's sample numbers from page 6-12 of a thirty-year-old POH — accurate for the example airplane and wrong for every airplane that ever flew off the line. Or it's a developer's guess. Both fail open: they hand the pilot a number that LOOKS authoritative and isn't.
Software that's wrong-but-confident in aviation is worse than software that asks for one more input.
The right number lives on a sticker in the airplane
Every aircraft has a current weight-and-balance record, usually a yellow card in the back of the POH. That card is the only source of truth. Re-weighed at major modifications. Updated when avionics are installed. Signed by an A&P.
If a software tool encourages a pilot to skip looking at that card — to pick "C172" from a dropdown and trust whatever the developer typed in — the tool is contributing to a worse flight, not a better one.
This is the same principle that runs AutoBrief
The same rule applies in AutoBrief. We don't guess. The legal call is encoded against the actual CFR sections. The currency math floors to the end-of-month convention from §61.23. The medical durations are exactly the durations the regulation specifies. When something can't be deterministically known — like "did the pilot actually complete three takeoffs and three landings to a full stop?" — the engine asks. It doesn't infer.
You can hold any of our calculators up next to a current FAR or a current POH and verify them in five minutes. The lack of presets isn't a missing feature. It's the feature.
What this means for the eventual aircraft-presets feature
We'll probably build it eventually — but it won't be a dropdown. It'll be: enter your tail number once, type the numbers from YOUR W&B card once, and the calculator saves them for next time. Locally. In your browser. We never ship anyone else's numbers and call them yours.
The free tool is the pitch. The pitch is: we get the data lineage right. The day we hand you someone else's numbers is the day you stop being able to trust us.