# What are Runway Declared Distances?

Perusing through the A/FD in the United States I see that some runways have declared distances while others do not.

What is the meaning of:

1. TODA
2. TORA
3. ASDA
4. LDA

From the AIM, 4-3-6 (c)(2):

All 14 CFR Part 139 airports report declared distances for each runway. Other airports may also report declared distances for a runway if necessary to meet runway design standards or to indicate the presence of a clearway or stopway. Where reported, declared distances for each runway end are published in the Airport/Facility Directory (A/FD). For runways without published declared distances, the declared distances may be assumed to be equal to the physical length of the runway unless there is a displaced landing threshold, in which case the Landing Distance Available (LDA) is shortened by the amount of the threshold displacement.

Now for definitions. These terms are defined by the FAA/ICAO in the PCG.

TODA - Takeoff Distance Available. The takeoff run available plus the length of any remaining runway or clearway beyond the far end of the takeoff run available.

TORA - Takeoff run available. The runway length declared available and suitable for the ground run of an airplane taking off.

ASDA - Accelerate-Stop Distance Available. The runway plus stopway length declared available and suitable for the acceleration and deceleration of an airplane aborting a takeoff.

LDA - Landing Distance Available. The runway length declared available and suitable for a landing airplane.

(also Declared Distances from wikipedia)

Stopway - An area beyond the takeoff runway no less wide than the runway and centered upon the extended centerline of the runway, able to support the airplane during an aborted takeoff, without causing structural damage to the airplane, and designated by the airport authorities for use in decelerating the airplane during an aborted takeoff.

Clearway - An area beyond the takeoff runway under the control of airport authorities within which terrain or fixed obstacles may not extend above specified limits. These areas may be required for certain turbine-powered operations and the size and upward slope of the clearway will differ depending on when the aircraft was certificated.

then for those specified limits of the clearway, in 14 CFR Part 1 we find

Clearway means:

(1) For turbine engine powered airplanes certificated after August 29, 1959, an area beyond the runway, not less than 500 feet wide, centrally located about the extended centerline of the runway, and under the control of the airport authorities. The clearway is expressed in terms of a clearway plane, extending from the end of the runway with an upward slope not exceeding 1.25 percent, above which no object nor any terrain protrudes. However, threshold lights may protrude above the plane if their height above the end of the runway is 26 inches or less and if they are located to each side of the runway.

(2) For turbine engine powered airplanes certificated after September 30, 1958, but before August 30, 1959, an area beyond the takeoff runway extending no less than 300 feet on either side of the extended centerline of the runway, at an elevation no higher than the elevation of the end of the runway, clear of all fixed obstacles, and under the control of the airport authorities.

A small correction to “take off run available” part. It’s not only the ground run but also may include some air distance over clearway. But this distance may not be longer than one-half of the distance between lift off point and point where aircraft reaches 35 feet AGL.

It’s introduced by SR-422A back in 1958 to utilize clearways for turbine powered aircrafts. This concept basically allows aircrafts to operate at higher gross weights otherwise limited by available runway surfaces only.

• This is more appropriate as a comment. What country are you referring to? The definition for TORA came from the U.S. AIM 4-3-6. What you described is the TODA distance listed above. Jul 10 '20 at 3:29
• I got it from AC 25-7C take off section pg67-69. You’re right, AIM does not mention the air portion of it. Maybe they want to come up with a simplified version I guess. Or maybe I’m getting it wrong. Jul 10 '20 at 9:15
• Thanks for the reference. The "takeoff run" listed in the AC deals with the requirement for the airplane to reach 35 feet above the ground and it can use 1/2 the clearway to satisfy that requirement. I would agree with that statement. Declared distances, however, allow the airport to provide a safety margin for aircraft using that runway. TORA values do not account for clearways. TODA values do. For airplanes that want to use a clearway, they will have a method of separating accelerate-stop and accelerate-go takeoff numbers (or be provided separately) Jul 10 '20 at 13:15
• Yes, I agree. My intend was to clarify that the take-off run distance maybe longer than the actual concrete, TORA itself. That’s because you get credit for air distance part over the clear way. I can delete it if it’s not adding any value to discussion. Jul 11 '20 at 13:14