Aviation Calcs

Visual descent point

Visual Descent Point Calculator

Find the visual descent point for a non-precision approach: the distance from the threshold at which a chosen descent angle — 3° by default — reaches your height above touchdown (HAT). The exact slope and the common HAT/300 rule of thumb are both shown. Add a groundspeed for descent rate, or a threshold DME to get a VDP DME fix.

Or enter MDA and touchdown-zone elevation and HAT will be MDA − TDZE.

VDP from the threshold

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Where the VDP sits

The visual descent point is the point along the final approach course from which a normal (usually 3°) descent from the MDA reaches the runway. The exact distance from the threshold is

distNM = HAT / (6,076.12 × tan θ)

A 3.00° path is 318.4 ft/NM, so a 300 ft HAT gives a VDP 0.94 NM from the threshold. The common memory item is HAT / 300, which would call that same example 1.0 NM. This page reports the exact distance, the /300 rule, and (for comparison) a /320 rule.

Descent rate

Feet per minute on the path is fpm = (ft/NM) × groundspeedkt / 60. For a 3° path that is very nearly the “times five” rule (fpm ≈ GS × 5). At 90 kt, times-five is 450 fpm; the exact 3° rate is about 477 fpm. For a cruise descent to the airport, see the top of descent calculator.

Sources

FAA Instrument Flying Handbook (visual descent point); FAA Instrument Procedures Handbook; AIM / TERPS 3° glide-path design. A computed VDP is not a TERPS fix unless it is charted.

Frequently asked questions

Is HAT the same as MDA?

No. HAT is height above the touchdown zone. If you know MDA and TDZE, HAT = MDA − TDZE. Use the published figures from the approach chart.

Why do some schools teach HAT/300 and others HAT/320?

A 3° slope is 318 ft/NM, which is close to both 300 and 320. HAT/300 is the more common U.S. memory item and is slightly conservative (it puts the VDP a little farther out). This page shows the exact tan(θ) distance as the primary figure.

What if the chart already has a VDP?

Fly the published, charted VDP. A number you compute here is only a planning aid, and it may differ from the charted location because of how the procedure was designed.