Before every flight, most pilots check the runway length and compare it to their aircraft's required takeoff and landing performance. That part is straightforward. But here's what many pilots, especially those newer to the industry, don't fully appreciate: the number printed on the airport diagram is not necessarily the number you should be using for your performance calculations.
Runway declared distances tell a more complete story. They account for obstacles, highway clearances, stopways, displaced thresholds, and runway safety areas. Understanding the four declared distances, TORA, TODA, ASDA, and LDA, is essential for safe flight planning and legal compliance, whether you're flying a small piston aircraft or a transport category jet.
Why the Painted Runway Length Isn't the Whole Picture
Take a practical example. At Easton Airport (KESN) in Maryland, Runway 22 is listed as 5,500 feet on the airport diagram and on sectional charts. That figure represents the total physical pavement length. But not all of that pavement is available for every phase of flight.
Runway 22 has a displaced threshold at its approach end, meaning the first 325 feet of pavement cannot be used for landing. It can be used for taxiing and for beginning a takeoff roll, but not as a landing surface. On the opposite end of the runway, near Runway 4, there is a short taxiway extension that is marked in yellow and designated for taxiing only, not for starting a takeoff run. The likely reason for this restriction is jet blast protection, because U.S. Route 50 runs directly behind that end of the airport.
These kinds of real-world constraints are why the FAA publishes declared distances. You'll find them in the Chart Supplement (formerly the Airport/Facility Directory) under the runway information section for most larger airports. ICAO also uses the same four declared distances as a standard framework, so this concept applies globally, not just in the United States.
TODA: Takeoff Distance Available
Takeoff Distance Available (TODA) is the total length available for the takeoff roll and initial climb. It includes the full physical runway length plus any clearway beyond the runway end, if one exists. A clearway is a defined area beyond the runway over which an aircraft may begin its initial climb to a specified height. It is not pavement, but it is usable airspace for climb purposes.
At Easton's Runway 4, TODA is listed as 5,500 feet. This includes the displaced threshold at the far end of the runway (the Runway 22 threshold), because an aircraft taking off from Runway 4 can roll through that displaced zone. However, it does not include the yellow-marked taxiway extension at the beginning, because that surface is designated for taxiing only.
If a stopway existed beyond the runway end (an area usable for decelerating in an aborted takeoff, marked with yellow chevrons), it would not be included in TODA. Stopways count toward ASDA, which we'll cover below, but not toward TODA.
Pro tip: TODA is typically the largest of the four declared distances, because it can include clearways beyond the physical pavement. Always check whether a clearway exists before assuming TODA equals runway length.
TORA: Takeoff Run Available
Takeoff Run Available (TORA) is the length of runway available for the ground roll portion of takeoff only. It does not include any clearway or stopway. For most runways without special configurations, TORA equals the physical runway length from brake release point to the far end.
At Runway 4 in our Easton example, TORA is 5,175 feet, not 5,500. This is because the displaced threshold at the Runway 4 end is excluded. The decision was made, likely due to the highway behind the airport, that the takeoff run begins at the threshold of Runway 4, not at the very beginning of the pavement. The displaced zone is available for the takeoff roll only if operationally appropriate, and here it has been excluded from the declared TORA.
Contrast that with Runway 22, where TORA is the full 5,500 feet. There are no constraints on the departure end of Runway 22, so the full runway length is available for the ground roll.
ASDA: Accelerate-Stop Distance Available
Accelerate-Stop Distance Available (ASDA) is the distance available for an aircraft to accelerate to decision speed, reject the takeoff, and come to a complete stop. This is a critical number for jet operations, particularly when calculating V1 speeds and rejected takeoff performance.
ASDA equals TORA plus any stopway available beyond the runway end. At many larger airports, especially those with high-speed jet traffic, ASDA can exceed the physical runway length significantly when a stopway or arresting system is present.
At Runway 4 in Easton, ASDA is listed as only 4,775 feet, which is actually shorter than TORA. This is because Route 50 constrains not just the pavement markings but also the Runway Safety Area (RSA), the graded buffer zone required by FAA standards around runways that allows aircraft to safely overrun without catastrophic consequences. A highway running behind the threshold does not qualify as part of an RSA, so the usable stop distance is reduced accordingly.
This is an important reminder: ASDA is not just about pavement. It includes safety margins and environmental factors that the airport authority has factored into the declared value.
Did you know? ICAO Annex 14 defines all four declared distances and requires airports above a certain category to publish them. For international operations, always cross-check declared distances in the relevant AIP (Aeronautical Information Publication) for the country you're operating in.
LDA: Landing Distance Available
Landing Distance Available (LDA) is the runway length declared suitable for the ground roll after touchdown. It begins at the landing threshold, which may be displaced, and ends at the far end of the runway. Unlike TODA, LDA never includes clearways or stopways.
For Runway 4 at Easton, LDA is 4,775 feet. This matches the ASDA figure, and for the same reason: Route 50 and the RSA constraints limit how much of the pavement is declared usable for landing operations. Note that a legal landing can physically continue all the way to the end of the runway and onto the connecting taxiway, but for performance planning purposes, you must use the declared 4,775 feet.
For Runway 22, LDA is 5,175 feet. The displaced threshold of 325 feet reduces the full 5,500-foot runway length because landings cannot touch down in the displaced zone. The math here is simple: 5,500 minus 325 equals 5,175. But do not assume this subtraction always works cleanly for other runways.
On instrument approaches, LDA values are published directly on the approach plate. For KESN, Runway 4 shows a landing distance of 4,775 feet and Runway 22 shows 5,175 feet at the top of their respective approach plates. This is your official reference for IFR performance planning.
A Common Mistake: Don't Do the Math Yourself
One of the most tempting shortcuts pilots take is calculating their own effective LDA by taking the published runway length and subtracting the displaced threshold. It feels logical, and for Runway 22 at Easton, it even gives you the right answer.
But it does not work for Runway 4. The declared LDA there is 4,775 feet, not 5,175 feet (which is what you'd get by subtracting 325 feet from 5,500). The difference comes from factors that are not printed anywhere obvious, things like RSA compliance, safety area geometry, obstacle clearance requirements, and local infrastructure constraints like the highway.
Always use the published declared distances. They are the product of engineering surveys, regulatory review, and site-specific analysis. Your mental arithmetic, however reasonable, cannot replicate that.
Pro tip: For airports where declared distances are not published (common at smaller GA fields), the runway length shown on the airport diagram is your working reference. But be aware that displaced thresholds still restrict where you can legally land, even if no formal LDA is published.
Where to Find Declared Distances During Flight Planning
For U.S. airports, declared distances are published in the FAA Chart Supplement, under the runway information section. They appear as a table with four rows for each runway direction: TORA, TODA, ASDA, and LDA, each in feet.
For international operations, you'll find equivalent data in each country's AIP. When planning flights into China, Russia, or other countries with specific permit requirements, declared distance data is often bundled with other operational data in the AIP En Route and AD (aerodrome) sections. Cross-checking this data before departure is a standard step in professional dispatch and flight planning.
Platforms like Data Sky Center's U.S. airport database aggregate this kind of operational data, giving pilots and dispatchers quick access to airport information during preflight planning. You can look up runway data, approach procedures, and NOTAMs without jumping between multiple sources.
How This Applies to Your Performance Calculations
Performance charts in your Pilot Operating Handbook (POH) or Aircraft Flight Manual (AFM) give you required distances for takeoff and landing under given conditions: weight, altitude, temperature, wind, and runway surface. The number you compare against those required distances must be the appropriate declared distance, not just the runway length.
For takeoff, compare your required takeoff roll against TORA and your required takeoff distance (including initial climb) against TODA. For rejected takeoffs in jets, compare your accelerate-stop distance against ASDA. For landing, use LDA as your available runway in all calculations, including the FAA's required landing distance with the applicable safety factor.
Getting this right matters. Flying into a short runway at a high-altitude airport on a warm day with a full load leaves very little margin for error. Using the wrong declared distance in that scenario is not just a regulatory issue; it is a safety issue.
Key Takeaways
- TODA (Takeoff Distance Available) includes the runway plus any clearway. It is the longest of the four distances.
- TORA (Takeoff Run Available) covers the ground roll only, with no clearway or stopway included.
- ASDA (Accelerate-Stop Distance Available) adds any stopway to TORA, used for rejected takeoff planning, especially in jets.
- LDA (Landing Distance Available) starts at the landing threshold (which may be displaced) and ends at the runway's physical end.
- Displaced thresholds reduce LDA but may or may not affect TORA, depending on the airport's specific declared values.
- Do not calculate declared distances yourself. Always use published values from the Chart Supplement or AIP.
- LDA values appear on instrument approach plates for easy reference during IFR planning.
- Local constraints like highways, obstacles, and RSA requirements directly influence declared distances, even when those factors are not obvious from an airport diagram.
Plan Smarter With the Right Data
Understanding declared distances is one of those fundamentals that separates thorough preflight planning from a quick glance at the sectional. Whether you're landing a Cessna at a regional airport or dispatching a jet into an unfamiliar field, knowing which distance figure applies to which phase of flight keeps your performance planning accurate and legally sound.
Data Sky Center makes it easier to access this kind of operational airport data in one place. Use the airport search to look up runway information, approach plates, and declared distances before your next flight. Good planning starts with the right numbers.
