The 'Impossible Turn' Calculator (Turnback Analysis)
Engine failure after takeoff: the altitude a turnback to the runway actually requires — turn geometry, sink in the bank, and the headwind-becomes-tailwind kicker.
Why 270°? A 180 leaves you offset a diameter from the runway — the realignment S-turn adds ~90° more of turning. AOPA/FAA testing puts real-world minimums for trainers at 600–1,000 ft AGL with proficiency. Below YOUR practiced number: land ahead, wings level.
Formula
⚠️ For flight planning and education only — verify with your POH/AFM and official sources. Not for primary navigation or in-flight emergency decision-making without POH data.
Disclaimer: This tool is for general informational and estimation purposes only and is not professional financial, tax, accounting or legal advice. All figures are estimates — verify with a qualified professional before making decisions. Read the full disclaimer.
Engine failure after takeoff: the altitude a turnback to the runway actually requires — turn geometry, sink in the bank, and the headwind-becomes-tailwind kicker.
About The 'Impossible Turn' Calculator (Turnback Analysis)
No takeoff briefing item carries more accident history than the turnback. This calculator does the physics honestly: a return isn't a 180 but ~270 degrees of turning (offset plus realignment), flown at a sink rate inflated by bank loading, after seconds of stunned recognition — and it sums those into the height the maneuver consumes before your margins are added. The point isn't to enable the turn; it's to replace folklore with a number you then validate at altitude, with an instructor, for your aircraft.
How to use The 'Impossible Turn' Calculator (Turnback Analysis)
- 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 turn rate = g·tanφ/V; sink in bank ≈ clean sink × n^1.5; total ≈ 270° of turning + reaction + buffer substituted step by step.
- 4Adjust inputs (or flip the unit toggle) until the scenario matches yours, then copy or share the result.
Why use The 'Impossible Turn' Calculator (Turnback Analysis)?
- ✓Instant, free and private — every calculation runs in your browser, nothing is uploaded
- ✓Built on the published formula turn rate = g·tanφ/V; sink in bank ≈ clean sink × n^1.5; total ≈ 270° of turning + reaction + buffer with sources cited on the page
- ✓Why 270°? A 180 leaves you offset a diameter from the runway — the realignment S-turn adds ~90° more of turning. AOPA/FAA testing puts real-world minimums for trainers at 600–1,000 ft AGL with proficiency. Below YOUR practiced number: land ahead, wings level.
- ✓Switch units, tweak any input and watch every result update live
Frequently asked questions
Why is 45° of bank correct when instinct says shallow?+
Height lost per degree of turn is minimized near 45°: shallow banks turn so slowly that time (and sink) accumulate, while steeper banks pay accelerating load-factor sink penalties. Rogers' analysis puts the optimum around 45° at a speed just above the banked stall. Instinct's gentle 20° bank is the trap — it nearly doubles the height the turn consumes.
Why 270 degrees instead of 180?+
Geometry: a 180° turn returns you parallel to the runway but offset by a full turn diameter (this tool prints the radius). Realigning costs an S — roughly 45° beyond the reciprocal, then 45° back. Teardrop techniques trade some of this, but 270°-equivalent is the honest planning figure, and it's where the folklore '180 back' analysis goes optimistic by a third.
What does the wind do to a turnback?+
Mostly conspires: the headwind that shortened your takeoff becomes a tailwind on the return — raising ground speed and landing distance on a runway you'll reach displaced and high-energy — while the climb-out headwind means the failure point is closer to the field (the one mercy). Strong wind also demands turning INTO the crosswind first or drifting further from the centerline. Each knot tightens the decision against turning.
How do I establish my personal turnback altitude?+
At altitude, with a safety pilot: simulate the failure at a hard deck 'runway' (pick an altitude as ground), pull power, count a real three-second pause, then fly the full 270° profile at 45° and note the height consumed. Add 50% for the day you're startled, hot and heavy. Brief THAT number before every takeoff — below it, the nose goes down and the landing happens ahead, wings level, into whatever's there. Wings-level arrivals are overwhelmingly survivable; stall-spins from the turn are not.
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