Declared Distance Calculator — Tool Guide

Coming Soon AC 150/5300-13B CHG 1 · APPENDIX H · ALL GUIDES

The Declared Distance Calculator computes the four declared distances — Takeoff Run Available (TORA), Takeoff Distance Available (TODA), Accelerate-Stop Distance Available (ASDA), and Landing Distance Available (LDA) — for each runway end per AC 150/5300-13B Appendix H. You enter the physical runway geometry — length, displaced thresholds, stopways, clearways — plus optional intersection-takeoff offsets and obstacle clearance inputs, and the tool resolves each end's four distances with the adjustments flagged. An optional airport lookup pulls the published declared distances from FAA NASR so you can pre-fill from the current record and see at a glance whether your configuration matches what is published or constitutes a proposed change.

It replaces the usual workflow of laying out TORA/TODA/ASDA/LDA arithmetic in a spreadsheet end by end, cross-checking which input affects which distance, and hand-drawing the stopway/clearway/displaced-threshold relationships for the report figure.

This tool is built and in pre-release. It will open from the home page when released; this guide documents the full workflow.

Who It's For & When to Use It

Airport planners preparing declared-distance tables for ALPs, Airport Master Record updates, master plans, and runway alternatives analyses. Use it when evaluating a displaced threshold or stopway/clearway change, when assessing how an approach or departure obstacle would constrain LDA or TODA, when documenting an intersection-takeoff scenario, or when you need a clean per-end declared-distances table that reconciles against the published NASR record.

How to Use It

Optionally look up the airport (Airport Identity Bar). The optional airport section at the top is the shared Airport Identity Bar: a single FAA LID / ICAO field (it notes it prefills published declared distances) and a Look Up button. A bare three-letter US code is auto-prefixed with K (DEN → KDEN), so you can type either form. After a successful lookup the bar shows the airport name, identifier, and the active data source. For US airports with published declared distances in the current NASR cycle, a Pre-fill runways from NASR action appears that replaces the current runway blocks with the published geometry.
If the data came from OurAirports, acknowledge the banner. When AvPlot cannot serve authoritative FAA NASR data — a non-US facility or a NASR miss/outage — it falls back to OurAirports and the Airport Identity Bar raises a blocking fallback banner. OurAirports is community-maintained and non-authoritative, so the banner makes you choose: Continue with OurAirports data (proceed and verify independently) or Stop (clear it and enter declared distances manually). Nothing prefills from a fallback source until you continue. NASR does not cover non-US airports, so for those the bar reports that published declared distances are not available — enter distances manually.
Set up each runway block. Enter the End 1 number (1–36) and L/C/R suffix — End 2 is derived automatically as the reciprocal — and the physical runway length (required; nothing computes without it). Use + Add Runway for additional runways, up to six per session.
Enter per-end geometry. Each runway block shows a two-column grid, one column per end. For each end: Displaced Threshold (affects LDA only — takeoff aircraft may still use the full length), Stopway (affects ASDA only; a stopway serving this end's departures physically lies beyond the far end), and Clearway (affects TODA only; the tool warns and caps the value at half the runway length per the AC's clearway limit).
Open Intersection Takeoff if applicable. The collapsible section takes the distance from the threshold to the departure intersection; it reduces TORA, TODA, and ASDA on that end only and does not affect LDA.
Open Obstacle Analysis if applicable. For an approach-end obstacle, enter height AGL, distance from the threshold, and the approach surface type (Visual 20:1, Non-Precision/NPI 34:1, Precision CAT I 50:1, or Precision CAT II/III 50:1). If the obstacle penetrates the surface, the tool shows the worked required-displacement calculation and reduces LDA. For a departure-end obstacle, enter height AGL, distance from the departure end, and the departure surface type (Visual 20:1 or Instrument 40:1); a penetration limits the usable clearway and reduces TODA. Clear cases show the surface height and clearance margin instead.
Read the per-end results. Each end's mini-result card lists TORA, TODA, ASDA, and LDA, with an adjusted badge on any value that differs from the physical length and a capped badge when the clearway limit governed TODA. If you pre-filled from NASR, the card is also labeled As published (with the NASR cycle date) or Proposed (modified from published), and a green published-values panel below shows the current NASR TORA/TODA/ASDA/LDA for that end with a one-click Reset this end to published.
Check the diagram and summary table. Each runway block draws a to-scale plan diagram — runway, stopways, clearways, and displaced-threshold markers, labeled by end — and the summary table at the bottom lists all four distances for every configured end, with adjusted values highlighted.
Export. Copy Table puts the full declared-distances table on the clipboard as formatted text (with the airport identifier when one was looked up); Print opens the browser print dialog with a print stylesheet that strips the chrome (print or save to PDF from there). A RSA / ROFA / ROFZ Reference → link in the same action row jumps to the safety-area tool for the same runway.

Key Features

Airport Identity Bar with authoritative-source enforcement. A single FAA LID / ICAO field with K-prefix auto-add looks up the airport; US facilities resolve to FAA NASR, and any OurAirports fallback raises a blocking continue/stop banner so non-authoritative data is never used silently.
Published-vs-calculated comparison. NASR pre-fill carries the published TORA/TODA/ASDA/LDA per end (with cycle date) alongside your calculated values; each end is badged As published or Proposed, and any end resets to published in one click.
Multi-runway sessions. Up to six runway blocks, each with independent geometry, feeding a single combined summary table.
Input-to-distance traceability. Every input is tagged with the distance it affects (displaced threshold → LDA, stopway → ASDA, clearway → TODA, intersection offset → TORA/TODA/ASDA), and editing a field briefly highlights the affected result.
Intersection takeoff. Per-end intersection-departure offsets reduce TORA, TODA, and ASDA without touching LDA.
Obstacle clearance surfaces. Approach (20:1, 34:1, 50:1) and departure (20:1, 40:1) surface options with worked penetration, required-displacement, and clearway-limit calculations shown inline.
Runway diagram. A to-scale SVG per runway showing stopways, clearways, and displaced thresholds on the correct sides.
Copy and print export. Clipboard-ready text table and a print-clean Print export (print or save to PDF), plus a one-click link to the RSA / ROFA reference.
Instant client-side computation. Distances are computed in the browser by AvPlot's shared declared-distance utilities; results update as you type.

FAA References

AC 150/5300-13B Chg 1, Airport Design, Appendix H — declared distances: definitions and application of TORA, TODA, ASDA, and LDA.
AC 150/5300-13B Chg 1, ¶3.14.1 — clearway limit; the tool cites this paragraph when capping a clearway entry at half the runway length.
FAA NASR (28-day subscription) — source of the published declared distances and runway geometry used by the airport lookup; every pre-filled value carries its NASR cycle date.
OurAirports (community data, fallback only) — non-authoritative source used only when NASR cannot serve a facility (non-US coverage or a NASR miss/outage). It is surfaced behind a blocking continue/stop banner that must be acknowledged, and any value it supplies must be independently verified.

Limitations & Disclaimers

The tool carries its own disclaimer, which applies to everything it produces: declared distances shown are calculated values based on user inputs; obstacle analysis uses simplified FAA surface geometry per AC 150/5300-13B; and all declared distances must be verified by a licensed airport engineer and coordinated with the FAA Airports District Office before use in official Airport Layout Plans, Airport Master Records, or regulatory submittals.

Calculated values are only as good as the inputs — thresholds, stopways, clearways, and obstacle positions must come from survey or authoritative records, not estimates.
Obstacle analysis evaluates a single point obstacle per side against a single sloped surface; it is a planning-level screen, not an airspace or TERPS analysis.
NASR pre-fill carries published declared distances and displaced thresholds; stopway, clearway, and obstacle inputs still need to be entered from your own records where they apply.
AvPlot is technical planning production support — not a replacement for stamped engineering or construction documents.

Related Tools

Runway Linework Generator — draws the runway, safety areas, and RPZs (which anchor to declared-distance ends) as CAD-ready linework (guide).
RSA / ROFA / ROFZ Reference — safety area and object free area standards for the same runway (guide).
RPZ Dimensions — Runway Protection Zone dimensions; note that the departure RPZ position follows the takeoff run available end (guide).

Tips & Best Practices

Start from the NASR lookup whenever the airport is US-based: pre-fill the published record first, then layer your proposed changes on top so every end is explicitly badged published or proposed.
Reconcile any difference between your calculated values and the published panel before publishing a table — an unexplained delta usually means a missed stopway, clearway, or displaced threshold in the inputs.
Document obstacle sources and survey dates in your project notes; the tool computes from the height and distance you give it, and those numbers need a defensible origin in the report.
Watch the per-input “affects” tags when reviewing someone else's inputs — the most common declared-distance error is applying a stopway or clearway to the wrong end, and the tags plus the diagram make the geometry explicit.
Use Copy Table for the report appendix and keep the NASR cycle date with it, so the comparison baseline is traceable to a specific publication cycle.

Declared Distances Explained — TORA, TODA, ASDA, and LDA, with a worked example.
Understanding the Runway Design Code — the RDC context that frames declared-distance design.