Water Crossing Glide Planner
Shoreline-to-shoreline honesty: the altitude a water crossing needs for continuous glide coverage, the wet footprint that remains, and where the point of commitment sits.
Mid-crossing is the commitment line: before it, turn back; past it, press on. Great Lakes arithmetic is sobering — a 60-nm crossing needs ~21,000 ft for continuous coverage in a 9:1 single, which is why the northern shore route exists.
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.
Shoreline-to-shoreline honesty: the altitude a water crossing needs for continuous glide coverage, the wet footprint that remains, and where the point of commitment sits.
About Water Crossing Glide Planner
Direct across the lake saves twelve minutes, and the calculator that should price it rarely gets opened. This one does: for any crossing width and glide ratio, the altitude that keeps a shoreline reachable the whole way; for your actual altitude, the width of the wet gap where the only option floats — plus the mid-point commit line. The numbers are bracing (continuous coverage of Lake Michigan needs flight levels), which is exactly the information.
How to use Water Crossing Glide Planner
- 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 coverage altitude = (width/2) ÷ (ratio/6076) + buffer; wet gap = width − 2×(alt−buffer)×ratio substituted step by step.
- 4Adjust inputs (or flip the unit toggle) until the scenario matches yours, then copy or share the result.
Why use Water Crossing Glide Planner?
- ✓Instant, free and private — every calculation runs in your browser, nothing is uploaded
- ✓Built on the published formula coverage altitude = (width/2) ÷ (ratio/6076) + buffer; wet gap = width − 2×(alt−buffer)×ratio with sources cited on the page
- ✓Mid-crossing is the commitment line: before it, turn back; past it, press on. Great Lakes arithmetic is sobering — a 60-nm crossing needs ~21,000 ft for continuous coverage in a 9:1 single, which is why the northern shore route exists.
- ✓Switch units, tweak any input and watch every result update live
Frequently asked questions
What altitude covers a typical lake crossing?+
Half-width divided by glide reach per foot, plus your shoreline buffer: an 18-nm crossing in a 9:1 single needs ~7,600 ft; 30 nm needs ~12,000; the Great Lakes' wide routes need altitudes most normally-aspirated singles can't or won't use. The formula's symmetry (cover from BOTH shores) is why doubling the crossing more than doubles the required height above the buffer.
Is a short wet gap acceptable risk?+
That's a personal-minimums decision this tool refuses to make for you — but it prices it honestly: a 6-nm gap at 120 knots is three minutes of exposure per crossing. The aviation-actuarial view: piston engines don't know they're over water, but survivability after a ditching depends overwhelmingly on preparation (vests ON, not stowed; raft for cold water; egress briefing). Equip for the gap you accept.
Why does cold water change the calculus so much?+
Survival time: in 5–10 °C water (the Great Lakes most of the year), useful consciousness is minutes and survival without flotation under an hour — rescue must essentially watch you ditch. Warm-water gaps and cold-water gaps are different risks wearing the same arithmetic. Seasonal rerouting (the shoreline track in winter) is the professional pattern, not paranoia.
What does the commit point change operationally?+
Your immediate response to any anomaly: before the midpoint, the reflex is turn back (nearest dry option is behind); after it, press on. Engine roughness at 40% across calls for the reciprocal heading while you troubleshoot — at 60%, continuing. Briefing the line aloud before the shore drops behind ('commit at the dark blue water, about 9 miles') converts a panic decision into a prepared one.
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