Max Drift & Clock-Code Mental Wind Calculator
The pro's shortcut: max drift = wind ÷ TAS-in-miles-per-minute, scaled by the clock code — mental wind correction within a degree of the exact triangle.
Two memorized numbers run the whole system: your max drift for today's wind (one division) and the clock code (15 past = ¼, half past = ½, quarter to = ¾). RAF navigators crossed oceans on this arithmetic.
Formula
⚠️ For flight planning and education only — verify with official sources and certified equipment. Not for primary navigation.
The pro's shortcut: max drift = wind ÷ TAS-in-miles-per-minute, scaled by the clock code — mental wind correction within a degree of the exact triangle.
About Max Drift & Clock-Code Mental Wind Calculator
The exact wind triangle needs a computer; the max-drift method needs one division. Sixty times wind over TAS gives the worst-case crab; the clock code (degrees-off-course read as minutes, converted to quarters of an hour) scales it to your actual wind angle. This trainer runs the shortcut beside the exact solution so you can watch it land within a degree across the realistic envelope — and learn to fly headings from your head.
How to use Max Drift & Clock-Code Mental Wind Calculator
- 1Enter — sensible defaults are pre-filled so you see a worked result immediately.
- 2Read the live results: .
- 3Check the "With your numbers" line to see the formula max drift ≈ 60 × wind/TAS; WCA ≈ max drift × (angle/60, capped at 1) — the clock code substituted step by step.
- 4Adjust inputs (or flip the unit toggle) until the scenario matches yours, then copy or share the result.
Why use Max Drift & Clock-Code Mental Wind Calculator?
- ✓Instant, free and private — every calculation runs in your browser, nothing is uploaded
- ✓Built on the published formula max drift ≈ 60 × wind/TAS; WCA ≈ max drift × (angle/60, capped at 1) — the clock code with sources cited on the page
- ✓Two memorized numbers run the whole system: your max drift for today's wind (one division) and the clock code (15 past = ¼, half past = ½, quarter to = ¾). RAF navigators crossed oceans on this arithmetic.
- ✓Switch units, tweak any input and watch every result update live
Frequently asked questions
Why does 60 × wind/TAS give the maximum drift?+
It's the small-angle version of asin(wind/TAS) in degrees: a radian is 57.3°, rounded to 60 for mental math. With wind fully crosswise, sin(WCA) = wind/TAS, and for the angles GA flying produces (under 25°) the sine and the angle in sixtieths agree closely. The rounding to 60 conveniently matches the clock code's base.
How does the clock code scale the drift?+
Read the wind's angle off your course as minutes on a clock face and take that fraction of the hour: 15° off = quarter past = ¼ of max drift, 30° = half, 45° = ¾, 60°+ = the whole thing. The same code runs the headwind component in reverse. Two glances at the DG and the forecast, one multiplication — heading solved.
How accurate is the combined method?+
Within 1–2° of the exact triangle whenever wind is under about a third of TAS — i.e., nearly always in powered flight. The errors of the 60-approximation and the clock code's linearization partially cancel, which is why the pairing has survived since RAF navigators standardized it. This page's error readout lets you audit it against your own typical numbers.
When would I actually use this over the GPS?+
Holding a sensible heading the moment ATC turns you loose ('proceed direct' with the box still loading), instant sanity-checking of an EFB solution fed yesterday's wind, partial-panel or device-failure days, and oral exams. Mental DR isn't nostalgia — it's the cross-check layer that makes automation failures boring.
Related Field tools
Sunrise & Sunset Calculator
Exact rise, set, solar noon and day length for any place and date — the NOAA solar equations with the refraction fine print included.
● LiveGolden Hour & Blue Hour Calculator
Tonight's golden hour and blue hour, computed from sun elevation — the photographer's light windows with the angles that define them.
● LiveDay Length Calculator
Hours of daylight for any date and latitude, how fast it's changing, and the swing between your solstices.
● Live