Hindsight borrows the discipline that keeps aircraft flying — and points it, carefully and a little playfully, at a life. This page is the whole philosophy in one sitting: what the gauges mean, what they refuse to claim, and why version 2.0 added a Mission tab.
D is an odometer, never a health meter. It never runs backward, and the app never pretends otherwise. Good stretches slow it; nothing reverses it. Any instrument that implies healing-by-arithmetic is lying to you, so ours don't.
A fraction of a finite life, spent. Spending is not failure — it is the only way to fly. An aircraft that never leaves the hangar accumulates almost no fatigue, and no flight hours either.
Not the payment itself — the damage unit spent on a mission your material was never designed to fly. The aim of everything iSight builds is to help a person identify their material (the authentic inner "i," explored playfully in the Mind My Material test), identify their mission, and align the two.
A life spent only avoiding damage becomes a hangar queen — polished, preserved, forever preparing for an engagement that never comes. The hangar itself is honorable: depot maintenance and refit are how airframes get ready, and sometimes ground time is exactly the right mission. The guard exists because preparation must eventually meet an engagement — just as surely as spending damage units with no intrinsic return wastes the same life faster. Every gauge in these apps is checked against both failure modes; none valorizes flatness, and none valorizes burn.
That is the purpose, said plainly — and said quantitatively inside the engineering metaphor the apps already speak. Held lightly: a gauge, not a doctrine.
The instrument shows position; the person supplies meaning. Observations, not verdicts. Questions over declarations — "Rest, or drift?" is the house style, because only the pilot knows which. This is an experimental personal instrument, and it says so on the panel.
Real aircraft live under ASIP — the Aircraft Structural Integrity Program — a decades-old discipline for flying finite structures without surprises. Hindsight maps its own pieces onto that discipline loosely and on purpose: the analogies are working metaphors, not certification claims.
| In the app | In the hangar |
|---|---|
| Mission definition — pick a spectrum, name the mission (new in v2) | i5.1.2 — declared service life & intended usage: deciding what the airframe is for |
| Daily W entry — one number a day | Loads / environment spectra survey (L/ESS) |
| D and dD/dt — the damage index and its rates | Durability analysis · force-management metrics |
| Anchor calibration — D = 1.0 at your documented event | Test-point correlation |
| Daily mission engagement — the −1 / 0 / +1 entry (new in v2) | Individual usage tracking — actual spectrum vs. design spectrum |
| Modal Survey — ring-down, set point, daily jolt (new in v3.5) | i5.3.2.1 — the ground vibration test, a sub-task of Pre-Flight Verification under Task III: measuring the structure's own properties instead of assuming them |
| Mind My Material | Materials characterization |
Coming in later releases, in the same spirit: a damage-tolerance track (crack-growth with load-interaction — sequence finally matters) and a self-inspection interval in pure maintenance language. Both are on the bench, not on the panel yet.
Through v1.x, Hindsight measured spending with real care — and measured what the spending bought not at all. The Mission update adds that numerator, on the same one-way arithmetic:
Define the mission — the i5.1.2 move. Pick the spectrum you're flying — Fighter, Sailplane, Transport, Aerobatic, Trainer, Rescue, Test bed, or Depot — then name it in your own words. Created retroactively and edited freely, because you are annotating your own history and the record is older than the feature. One mission at a time; gaps are allowed and never counted against you. If you've taken Mind My Material, the spectra your material typically flies well are starred — a mirror held up next to the choice, never a match score.
Read the service log. The record partitions by mission, flatly: Mission X — 0.31 life-units over 2.1 years. No judgment attached, because the number doesn't carry one. Past missions stay reviewable — sometimes the hangar was exactly the right call, and the log should say so without apology.
Answer one question a day. "Did you build the mission today?" — −1 the day's behaviors undermined it or ran opposite, 0 stayed neutral or didn't engage, +1 engaged and built it. Deliberately behavioral, not "did it feel aligned": feelings echo the daily dial, and an honest instrument refuses to measure a thing with itself. If the log sits quiet for more than a week, the panel says so — flatly.
See the alignment map. Engagement across, damage rate up — the rate measured only against your own chronic pace. You are a dot with a twelve-week trail. The four positions read: Flying the mission hard (expensive and legitimate), Efficient cruise (material well-matched to mission), In the hangar (rest, or drift? only the pilot knows — and depot time is a scheduled part of every service life), and Paying without flying — the one pattern the instrument exists to flag, which is exactly why it gets the gentlest treatment on the panel, not the loudest.
An honest panel lists its blind spots next to its gauges. The fatigue model cannot tell a contented flatline from a depressed one — the engagement axis exists partly for that. Miner's rule is sequence-blind: the same days in any order sum to the same D. The default constants are calibrated to a single reference subject — a thirteen-year, 2,400-day record — pending study data, which is why calibrating to your own anchor matters and why every new gauge ships with an ⓘ sheet stating its experimental status. And none of these instruments will ever show you remaining life, time-to-critical, or a countdown of any kind. Spent is knowable; remaining is not.
The framework is best understood from inside the cockpit — one number a day, thirty seconds, and the gauges build themselves.