The amount of runway you can actually use is rarely the same in every direction, or even the same for taking off and landing, which is why each runway publishes four separate distances.
This is general educational information, not operational, legal, or regulatory advice. Rules differ by authority and change over time. Always verify against current official sources and follow your operator's approved procedures.
Why four distances, not one
A runway is a strip of pavement, but the distance available to you depends on what you are doing: rolling for take-off, climbing away, stopping after a rejected take-off, or landing. To capture that, every runway direction publishes four declared distances, defined in ICAO Annex 14 (Aerodromes) and published in the AIP. The same definitions appear in the FAA's Airport Design advisory circular (AC 150/5300-13B) and the FAA AIM, and in EASA's aerodrome design specification CS-ADR-DSN; ICAO, the FAA, and EASA agree on all four.
- TORA, take-off run available. The length of runway declared available and suitable for the ground run of an aircraft taking off.
- TODA, take-off distance available. TORA plus the length of any clearway beyond it.
- ASDA, accelerate-stop distance available. TORA plus the length of any stopway beyond it.
- LDA, landing distance available. The length of runway declared available and suitable for the ground run of a landing aircraft.
Clearway and stopway
Two pieces of ground beyond the runway end change the picture, and each helps exactly one distance.
A clearway is a defined rectangular area beyond the end of the take-off run, over which an aircraft can make part of its initial climb to a screen height, kept clear of obstacles and under the control of the aerodrome authority. It lengthens TODA only. Under EASA's aerodrome rules a clearway's length may not exceed half the take-off run available.
A stopway is a defined area beyond the end of the take-off run, prepared and able to support an aircraft during a rejected take-off. It lengthens ASDA only.
Neither a clearway nor a stopway adds to TORA, because neither is runway you can roll along for a normal take-off, and a clearway is no help at all if you have to stop.
A worked illustration
Take a runway with these published figures:
TORA = 2000 m.- a clearway of
200 mbeyond the end, soTODA = 2000 + 200 = 2200 m. - a stopway of
150 mbeyond the end, soASDA = 2000 + 150 = 2150 m. - a displaced threshold, so landing begins
100 malong the runway, givingLDA = 1900 m.
Reading these, a take-off can use 2000 m on the ground and a further 200 m of clearway for the climb; a rejected take-off has 2150 m to accelerate and stop; and a landing has only 1900 m, because the displaced threshold moved the usable surface inward. Four numbers, four different distances, from one runway.
Now move the starting point. Suppose you take off not from the full length but from an intersection 300 m along the runway. Your TORA falls to 2000 - 300 = 1700 m, and because TODA and ASDA are both built on TORA, they fall by the same 300 m, to 1900 m and 1850 m. The clearway and stopway beyond the far end have not changed, but everything measured from your new, later start point is shorter. That is exactly why an intersection departure must be worked on the reduced figures, never on the full-length ones printed for the runway.
How each is used
The declared distances feed your performance calculation. The take-off case is checked against TORA and TODA; the rejected take-off against ASDA, where the aircraft accelerates to a decision point and must stop within the distance available; and the landing against LDA. A larger aircraft's performance work balances these against each other (the balanced-field concept), while a light aircraft pilot checks the required take-off and landing distances from the flight manual against the declared distances for the conditions. The point is to compare like with like: the distance your aircraft needs against the distance the runway actually gives you.
Common pitfalls
- Assuming the whole runway is available for everything. A displaced threshold, a clearway, or a stopway means the four distances differ, often by hundreds of metres.
- Taking off from an intersection. An intersection departure shortens TORA, and the reduced figure, not the full-length one, is what you have.
- Treating a clearway as stopping room. Clearway helps the climb, not a rejected take-off; only stopway helps you stop.
- Ignoring the conditions. Slope, surface, wind, and temperature change the distance your aircraft needs, even though the declared distances themselves are fixed.
In Pilot EFB
Pilot EFB does not calculate runway performance or declared-distance margins, and it is not a certified Electronic Flight Bag. It is a study and planning aid that keeps your weather, NOTAMs, flight time, and logbook in one offline-first place. Take the declared distances from the AIP for the aerodrome, work your required distances from the approved aircraft flight manual, and follow your operator's performance procedures. Saved data stays readable offline; pulling fresh data needs a connection.