Glide Range Ring & Cruise Altitude Planner
Pick cruise altitude by glide footprint: the reachable circle at each altitude, terrain-clearance subtraction, and the gaps where no airport is reachable.
Altitude is stored glide: each 1,000 ft buys ~1.5 nm of reach in a typical single. Route planning against the airport map with this ring is what turns 'direct' into 'direct, via gliding distance of something' — often for two extra minutes.
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.
Pick cruise altitude by glide footprint: the reachable circle at each altitude, terrain-clearance subtraction, and the gaps where no airport is reachable.
About Glide Range Ring & Cruise Altitude Planner
Glass cockpits draw it live, but the planning version matters more: at any cruise altitude, the glide ring's radius — height above terrain (minus the pattern height you refuse to arrive without) times glide ratio — defines a corridor of covered airports along your route. This calculator computes the ring and corridor width, and prices each thousand feet of climb in nautical miles of reach, which is the honest argument for cruising higher than the haze layer suggests.
How to use Glide Range Ring & Cruise Altitude 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 usable height = cruise − terrain − pattern; ring = usable × ratio; corridor = 2 × ring substituted step by step.
- 4Adjust inputs (or flip the unit toggle) until the scenario matches yours, then copy or share the result.
Why use Glide Range Ring & Cruise Altitude Planner?
- ✓Instant, free and private — every calculation runs in your browser, nothing is uploaded
- ✓Built on the published formula usable height = cruise − terrain − pattern; ring = usable × ratio; corridor = 2 × ring with sources cited on the page
- ✓Altitude is stored glide: each 1,000 ft buys ~1.5 nm of reach in a typical single. Route planning against the airport map with this ring is what turns 'direct' into 'direct, via gliding distance of something' — often for two extra minutes.
- ✓Switch units, tweak any input and watch every result update live
Frequently asked questions
How do I apply the corridor to route planning?+
Draw (mentally or in your EFB) the corridor — twice the ring width — along your course and see which airports fall inside: gaps are the stretches where an engine failure means a field, not a runway. Closing a gap usually costs little: 2,000 ft more altitude widens the corridor ~6 nm, or a 10° dogleg threads between covered zones. The exercise takes two minutes and changes routes surprisingly often.
Why subtract pattern height instead of gliding to the threshold?+
Because arriving at zero altitude at the field boundary is an arrival, not an approach: no ability to judge wind, slip away excess, dodge the ditch, or fix a misjudged base turn. A 1,000-ft arrival buys an abbreviated pattern and choices. The subtraction costs ~1.5 nm of ring radius and converts the remaining number from theoretical to usable.
Does terrain elevation really matter that much?+
It's the silent variable: 8,500 ft cruise over 1,500 ft terrain is 7,000 usable; the same cruise over a 6,000 ft plateau is 2,500 — a ring shrunk to a third. Mountain routes at 'normal' cruise altitudes often have effectively no ring at all, which reframes both the altitude choice and the canonical advice to cross ranges at maximum practical height.
Is this why 'altitude is life insurance' gets repeated?+
Precisely — and the premium is minutes: climbing from 6,500 to 10,500 in a typical single costs ~6 minutes and buys ~6 nm more ring (a corridor 12 nm wider), plus more time for restart attempts, radio calls and planning in any failure. The trade reverses only when oxygen rules, winds, or airspace argue otherwise. The ring math turns the aphorism into arithmetic.
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