Turn Radius & Diameter Calculator
How much sky a turn consumes: radius and diameter from speed and rate (or bank) — the canyon-turn and valley-flying number nobody computes until it matters.
V² is the lesson: slowing from 120 to 85 knots halves the turning circle — which is why the canyon-turn procedure is slow down first, then bank. At 120 kt and 30°, the 180 needs over half a nautical mile of valley width.
Formula
⚠️ For flight planning and education only — verify with official sources and certified equipment. Not for primary navigation.
How much sky a turn consumes: radius and diameter from speed and rate (or bank) — the canyon-turn and valley-flying number nobody computes until it matters.
About Turn Radius & Diameter Calculator
The turn that matters most — reversing course in a narrowing valley — is governed by a formula pilots meet only after it's urgent: radius equals speed squared over g-tan-bank. This calculator turns speed and bank into radius and the 180°-reversal diameter in feet and nautical miles, making vivid the two levers in order of power: slowing down (squared!) beats banking harder, which is precisely how the canyon-turn procedure is sequenced.
How to use Turn Radius & Diameter 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 r = V²/(g·tan φ) — radius grows with speed SQUARED, shrinks with bank substituted step by step.
- 4Adjust inputs (or flip the unit toggle) until the scenario matches yours, then copy or share the result.
Why use Turn Radius & Diameter Calculator?
- ✓Instant, free and private — every calculation runs in your browser, nothing is uploaded
- ✓Built on the published formula r = V²/(g·tan φ) — radius grows with speed SQUARED, shrinks with bank with sources cited on the page
- ✓V² is the lesson: slowing from 120 to 85 knots halves the turning circle — which is why the canyon-turn procedure is slow down first, then bank. At 120 kt and 30°, the 180 needs over half a nautical mile of valley width.
- ✓Switch units, tweak any input and watch every result update live
Frequently asked questions
Why does speed dominate turn radius so completely?+
It enters squared while bank enters through a tangent: 120→85 knots cuts the radius in half; 30°→45° of bank cuts it 42% but raises stall speed 19% and load factor to 1.41g simultaneously. In a tight spot the airspeed lever is both stronger and safer — full flaps and best-angle speed before steep bank is the canonical order.
How much room does a real course reversal need?+
The diameter plus drift and judgment margin: at 90 kt and 45° bank the circle is ~1,450 ft across — but wind drift during the 20-second turn, the wingspan, and the fact that you started somewhere inside the valley (not hugging the wall) realistically demand 2,500+ ft of width. Mountain instructors teach entering valleys on the updraft side partly to bank this width.
What does the same formula say about traffic patterns?+
That base-to-final overshoots are geometry, not skill: a 70-kt trainer at 20° bank turns in a 1,100-ft radius, but a 90-kt approach at the same bank needs 1,800 ft — the runway centerline arrives early, the temptation to steepen (or worse, skid) follows. Flying the same pattern speed every time makes the geometry repeatable; this tool shows what each extra 10 knots costs.
Does wind change the turn radius?+
Not through the air — the circle is fixed in the air mass — but the ground track becomes a cycloid: tightened upwind, stretched downwind. A canyon reversal begun downwind therefore consumes extra ground exactly when ground is the scarce resource, which is why the procedure says turn INTO the wind side. Radius over the ground, not the air, is what canyon walls measure.
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