Single-Engine Climb Gradient Calculator (Light Twins)
The multiengine truth-teller: OEI climb rate at today's density altitude converted to gradient, against terrain — where 'positive rate' meets 'positive enough.'
Light twins certify with no minimum OEI climb requirement below 6,000 lb — losing one of two engines costs 80%+ of excess power, not half. The gradient, not the rate, decides whether the second engine is transportation or consolation.
Formula
⚠️ For planning and education only. Weight & balance must be computed from YOUR aircraft's actual empty weight, arm and current equipment list, and verified against the POH/AFM envelope before flight.
The multiengine truth-teller: OEI climb rate at today's density altitude converted to gradient, against terrain — where 'positive rate' meets 'positive enough.'
About Single-Engine Climb Gradient Calculator (Light Twins)
The multiengine rating's central disillusionment is arithmetic: an engine failure removes half the power but 80-plus percent of the climb, because climb lives on power excess. This calculator delivers the number that matters after the feather drill — single-engine gradient at today's density altitude, in ft/nm against real terrain — using the linear climb-to-ceiling model anchored to your POH's OEI figures, with a verdict that quotes the standard every twin pilot should compare against before filing.
How to use Single-Engine Climb Gradient Calculator (Light Twins)
- 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 ROC_OEI(DA) ≈ ROC₀ × (1 − DA/abs ceiling); gradient = ROC × 60/GS substituted step by step.
- 4Adjust inputs (or flip the unit toggle) until the scenario matches yours, then copy or share the result.
Why use Single-Engine Climb Gradient Calculator (Light Twins)?
- ✓Instant, free and private — every calculation runs in your browser, nothing is uploaded
- ✓Built on the published formula ROC_OEI(DA) ≈ ROC₀ × (1 − DA/abs ceiling); gradient = ROC × 60/GS with sources cited on the page
- ✓Light twins certify with no minimum OEI climb requirement below 6,000 lb — losing one of two engines costs 80%+ of excess power, not half. The gradient, not the rate, decides whether the second engine is transportation or consolation.
- ✓Switch units, tweak any input and watch every result update live
Frequently asked questions
Why does losing 50% of power cost 80%+ of climb?+
Climb rate is proportional to power available minus power required — the excess. A twin needing 140 hp to fly level with 320 total has 180 excess; lose an engine (and add windmill/control drag, raising required power) and perhaps 30 remain. Half the installed power, a sixth of the climb. The certification rules acknowledge it: under 6,000 lb / 61 kt Vso, light twins need not demonstrate any OEI climb at all.
What is the OEI service ceiling and why is it so low?+
The density altitude where the OEI climb decays to 50 ft/min (note: 50, not the all-engine 100). Typical light twins post OEI ceilings of 5,000–8,000 ft — meaning that at western US density altitudes, many are below their OEI ceiling while parked. Above it, an engine failure begins a drift-down, and this tool's gradient goes negative in spirit.
How should this number change my departure briefing?+
It converts 'we'll come back around' into a tested claim: at 280 ft/nm OEI you can honestly out-climb the standard surface; at 90 ft/nm you cannot, and the brief should pre-select the landing option straight ahead — exactly the single-engine mindset, with feathering added. The gradient computed at today's DA and weight IS the briefing.
Does Vyse (blue line) guarantee the published climb?+
Vyse delivers the best available OEI rate — the POH number only with the failed prop feathered, gear up, flaps up, 3–5° bank into the live engine, and ball half out. Each omission costs: windmilling alone can erase 200+ ft/min, gear 150, sloppy trim 50–100. The published figure is a ceiling earned by procedure, not an entitlement of the speed.
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