TODA – Takeoff Distance Available (Declared Runway Distances): Airport Planning Glossary

Overview: Declared Runway Distances in Airport Planning

Declared runway distances are regulatory values, published by authorities such as the FAA and ICAO, that define the portions of a runway and its associated areas available for aircraft takeoff and landing operations. The four main declared distances—Takeoff Run Available (TORA), Takeoff Distance Available (TODA), Accelerate-Stop Distance Available (ASDA), and Landing Distance Available (LDA)—are critical for ensuring safe aircraft operations, guiding how pilots, dispatchers, and airport planners determine aircraft performance, operational limits, and regulatory compliance.

Declared distances are not merely measurements of pavement; they are carefully calculated based on runway geometry, safety areas, clearways, stopways, displaced thresholds, obstacles, and other operational factors. These values ensure compliance with national and international regulations, such as FAA Advisory Circular 150/5300-13B and ICAO Annex 14 , which establish standards for runway design, obstacle clearance, and safety.

Only officially published declared distances may be used for planning, dispatch, or in-flight decisions. Regulatory sources strictly prohibit recalculating declared distances by simply adding or subtracting clearway or stopway lengths. These values account for more than physical length: they include safety margins, obstacle clearance, pavement strength, and operational constraints.

Understanding declared distances is vital for safe and efficient airport planning. They impact the maximum allowable takeoff and landing weights, influence runway investments, and affect operational flexibility—especially during adverse conditions like wet or contaminated runways. Real-world examples, such as the length restrictions at Los Angeles International Airport (LAX) or displaced thresholds at Miami-Opa Locka Executive Airport (KOPF), demonstrate the operational impact of declared distances.

Key Declared Distances: Definitions and References

Regulatory Framework

Declared distances are defined by both U.S. and international authorities. U.S. standards are set forth in FAA Advisory Circular 150/5300-13B and the Aeronautical Information Manual (AIM 4-3-9). ICAO Annex 14 provides global standards and recommended practices.

Main Declared Distances

• TORA (Takeoff Run Available): The runway length available for the aircraft’s ground run during takeoff.
• TODA (Takeoff Distance Available): The sum of TORA plus any clearway, indicating the total length available for takeoff, including the initial airborne segment.
• ASDA (Accelerate-Stop Distance Available): The runway plus stopway length suitable for accelerating and, if necessary, aborting the takeoff and stopping the aircraft.
• LDA (Landing Distance Available): The runway length suitable for landing, starting at the landing threshold.

These definitions are harmonized between the FAA and ICAO, with minor differences in calculation or application. Declared distances are published in official documents like the FAA Chart Supplement and Jeppesen charts. Only published values may be used for performance and planning.

Takeoff Distance Available (TODA)

TODA is a declared distance representing the total length available for an aircraft to accelerate, lift off, and begin initial climb, including both the runway (TORA) and any designated clearway beyond the runway end.

How TODA Is Calculated

TODA = TORA + Clearway

• If no clearway exists, TODA equals TORA.
• The clearway is a specially designated area, at least 500 feet wide, obstacle-free, and under airport operator control, extending beyond the runway.

Example:
If a runway has a TORA of 7,000 feet and a clearway of 1,000 feet, the TODA is 8,000 feet.

Operational Use of TODA

• Only aircraft certified to use clearway may use the full TODA in performance calculations.
• Clearway cannot be used for rejected takeoff stopping; only ASDA (runway + stopway) is used for accelerate-stop calculations.
• In wet or contaminated runway conditions, clearway is typically not included in takeoff calculations.
• Aircraft Flight Manuals (AFMs) specify if clearway can be used in calculations.

Regulatory and Safety Considerations

• Clearway must be obstacle-free, level, and load-bearing but need not be paved.
• It is marked with yellow chevrons and not intended for stopping an aircraft.
• If a takeoff must be rejected, the aircraft must stop within ASDA, not TODA.

Airport Planning and TODA

• Including a clearway can increase TODA cost-effectively, but only if it meets regulatory criteria.
• The benefit depends on aircraft type, certification, and operational rules.
• TODA is always published in official aeronautical documents.

Related Declared Distances

Takeoff Run Available (TORA)

TORA is the runway length available and suitable for the ground run during takeoff. It may be less than the physical runway length due to safety areas or displaced thresholds. TORA is the primary distance used for takeoff roll calculations.

Accelerate-Stop Distance Available (ASDA)

ASDA is the length of runway plus stopway available for an aircraft to accelerate and, if necessary, abort takeoff and stop safely. If no stopway exists, ASDA equals TORA.

Landing Distance Available (LDA)

LDA is the declared runway length available for landing, measured from the landing threshold to the runway end (or to a point limited by displaced thresholds or obstacles). LDA is vital for ensuring the aircraft can safely land and stop.

Supporting Concepts

Clearway

A clearway is an obstacle-free area at least 500 feet wide beyond the runway, under airport operator control, designated for takeoff. It may be unpaved, must be free of obstacles, and is not suitable for stopping aircraft. Clearway extends TODA but not ASDA.

Stopway

A stopway is a paved area aligned with the runway, designed to support an aircraft during an aborted takeoff. It is included in ASDA but not in TODA.

Runway Safety Area (RSA)

RSA is a graded, obstacle-free area surrounding and extending beyond the runway, intended to minimize aircraft damage in case of an overrun or excursion. The configuration of the RSA can affect declared distances.

Displaced Threshold

A displaced threshold is a threshold located at a point other than the start of the runway. The area before the displaced threshold may be used for takeoff but not for landing. Displaced thresholds reduce LDA but may not affect TORA or ASDA.

Practical Application: Performance Calculations and Airport Planning

Pilots and dispatchers use declared distances for calculating takeoff and landing performance. The Aircraft Flight Manual provides charts based on aircraft weight, configuration, weather, runway slope, and surface condition, as well as available declared distances (TORA, TODA, ASDA, LDA).

• The most restrictive of these distances for a given operation is the limiting factor.
• For takeoff, if ASDA is shorter than TORA, the accelerate-stop calculation must use the shorter ASDA.
• For landing, if a displaced threshold reduces LDA, the landing performance must be based on the shorter LDA.

Declared distances directly influence airport design and infrastructure investment. Runway extensions, clearways, stopways, and displaced thresholds are often added or modified to support new aircraft types, improve safety margins, and comply with evolving regulations.

Real-World Example

At some airports, a runway may have a physical length greater than the declared TORA or LDA due to safety area or obstacle considerations. For instance, if a road or terrain feature prevents extending the safety area, the declared distances must be reduced to maintain compliance.

Summary

• TODA is a declared distance used for takeoff performance, equal to TORA plus any clearway.
• Only published declared distances from official sources may be used for operations.
• TODA is critical for regulatory compliance, aircraft performance planning, and airport design.
• The inclusion of clearway in TODA is subject to regulatory and aircraft-specific limitations.
• Declared distances ensure safe, efficient operations and guide airport development for current and future needs.

For more on declared distances and airport planning, consult FAA Advisory Circular 150/5300-13B , ICAO Annex 14 , and official aeronautical charts.

Sources: FAA, ICAO, SKYbrary, Jeppesen, Aeronautical Information Manual (AIM), FAA Chart Supplement