1 — What Takeoff Distance Actually Measures
The POH gives you two numbers. Know exactly what each measures before using the charts.
The two phases of takeoff distance
EASA exam trap
When a question asks for “takeoff distance” it almost always means the total distance to clear the 50 ft screen — not just the ground roll. Read carefully.2 — How Do You Read the POH Takeoff Chart?
Every aircraft has its own charts giving a base distance for standard conditions at a pressure altitude and temperature. You then correct for non-standard conditions on top.
Simplified POH — takeoff distance to 50 ft (metres)
| Pressure altitude | Temperature | ||
|---|---|---|---|
| ISA −10 | ISA | ISA +10 | |
| Sea level | 430 m | 480 m | 545 m |
| 2,000 ft | 470 m | 520 m | 600 m |
| 4,000 ft | 530 m | 590 m | 680 m |
| 6,000 ft | 600 m | 680 m | 780 m |
| 8,000 ft | 690 m | 790 m | 915 m |
Illustrative SEP at MTOW, paved, calm, level. Real questions use your aircraft’s POH.
If your pressure altitude or temperature falls between values, interpolate proportionally. E.g. at PA 3 000 ft, ISA: halfway between 520 m and 590 m = 555 m.
3 — How Do You Apply Takeoff Correction Factors?
The chart gives the base distance; real conditions are rarely standard. Apply each factor in sequence by multiplying the running total.
Standard correction factors
Headwind (per 10 kt)
-10%
Tailwind (per 10 kt)
+20%
Dry grass surface
+15%
Wet grass
+25%
Upslope (per 1%)
+10%
Downslope (per 1%)
-5%
How to apply them
Base × wind factor × surface factor × slope factor = final TODR. Order doesn’t change the maths, but step-by-step reduces errors. Every one of these factors — including the grass-runway factors — comes straight from the AFM/POH; a soft, wet or long grass surface costs more than a firm dry one.4 — Build Your Scenario
Pick conditions and watch each correction stack on top of the base distance.
Build your scenario
Distance breakdown
Base only With corrections
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5 — Worked Example (Exam-Style)
Given elevation 1 500 ft · QNH 1 001 hPa · OAT 28 °C · 10 kt headwind · dry paved · level:
- Pressure altitude: PA = 1500 + (1013 − 1001) × 30 = 1 860 ft → use the 2 000 ft row.
- ISA deviation: ISA at 2 000 ft = 11 °C; OAT 28 °C → ISA +17 → base ≈ 600 m (ISA +10 column).
- Wind: 10 kt headwind → −10% → 600 × 0.90 = 540 m.
- Surface & slope: dry paved, level → no correction.
Safety factor
In real planning, add a safety factor (typically ×1.25–1.33) on top of the POH figure — the book values assume a skilled pilot in ideal conditions.6 — Performance Class and the Reference Speeds
Two pieces of vocabulary the exam expects you to have, even though they sit underneath every chart you just used.
Performance Class B (CS-23 light aeroplanes)
Light aeroplanes like ours are certified under CS-23 and operated under Performance Class B — the class the applicable operational requirements (Part-NCO) assume. Its consequence for you: the POH gives unfactored book distances, measured by a test pilot in ideal conditions, and it is you who adds the safety factor and corrections to reach a usable planning number.The reference speeds: vS, vS0, vS1, vR
vS — the stall speed, the minimum steady speed at which the aircraft is controllable. vS0 — stall speed in the landing configuration (full flap): the bottom of the white arc. vS1 — stall speed in a defined configuration, usually clean: the bottom of the green arc. vR — rotation speed: the POH speed, just above vS1, at which you raise the nose to lift off. (The climb speeds Vx and Vy are in Lesson 3.)7 — Wind Components, Flap and the Go/No-Go
The chart corrects for the headwind component along the runway, not the raw wind — so when the wind is at an angle you must resolve it:
Resolving the wind
For a wind θ off the runway heading: headwind = wind × cos θ, crosswind = wind × sin θ. The quick clock rule: 30° ≈ ½, 45° ≈ ¾, 60°+ ≈ full crosswind (and the reverse for the headwind part). A 20 kt wind 30° off gives ≈ 17 kt headwind and ≈ 10 kt crosswind — use the headwind part on the chart and check the crosswind against the aircraft’s limit.The decision: TODR vs TODA
A distance figure only answers the real question when you compare it to the runway: take the factored take-off distance required (TODR) and confirm it is ≤ the take-off distance available (TODA), with margin. If it isn’t — wait for cooler air or more headwind, offload, or use a longer runway. The charts are also valid only for the mass range printed on them: interpolate within it, never extrapolate beyond it.Why a take-off flap setting helps
A small take-off flap setting (as the POH specifies) raises the lift at a lower speed, so the aeroplane lifts off sooner and the ground run is shorter. Too much flap adds drag and flattens the climb, so you use the published setting — not more.Knowledge Check
Question 1
The POH shows 480 m at sea level, ISA, calm, paved, level. The runway is dry short grass. Corrected distance?
Question 2
Base distance 600 m with a 10 kt tailwind. Corrected distance (≈ +20% per 10 kt tailwind)?
Question 3
Base distance 550 m, runway slope 1% uphill. What correction applies?
Question 4
Which scenario needs the longest takeoff distance?
Question 5
Light single-engine aeroplanes are operated under which performance class?
Question 6
vR is best described as the:
Question 7
The wind is 20 kt at 30° off the runway heading. The headwind component for the chart is about:
