The Chart Supplement and decoding an unfamiliar airport before you ever see the runway

The FAA Chart Supplement — formerly called the Airport/Facility Directory — is the single most important preflight resource for decoding an unfamiliar airport before you ever see the runway. Published every 56 days, it contains detailed entries for every public-use airport, seaport, and heliport in the United States, covering everything from field elevation and runway specs to traffic pattern direction and wildlife hazards. Knowing how to read it quickly and extract what matters is a skill the Airman Certification Standards explicitly require — and one that can keep you out of trouble at an airport you’ve never visited.

What Information Does the Chart Supplement Actually Contain?

Many student pilots think the Chart Supplement is just a list of radio frequencies. It’s far more than that. Each airport entry includes:

• Airport name, city, state, and identifier
• Field elevation above mean sea level
• Geographic coordinates (latitude and longitude)
• Runway designations, length, width, surface type, and condition
• Lighting systems and activation methods
• Communication frequencies for every service
• Remarks covering traffic patterns, noise abatement, obstructions, and hazards

Every one of these fields has practical implications for how you plan and fly your approach.

Why Does Field Elevation Matter So Much?

The field elevation appears near the top of every entry, and students often skip right past it. If you’ve been training at a sea-level airport and you’re flying to a field at 3,000 feet MSL, several things change immediately.

Your ground speed on approach will be higher than you’re used to. Your true airspeed at pattern altitude will be faster. On a warm day, your density altitude could be significantly higher than anything you’ve trained in. That single number should trigger a performance calculation before you go.

How Do I Decode the Lighting Abbreviations?

The lighting section uses abbreviations that matter most when you’re arriving near dusk or at night:

• MIRL — Medium Intensity Runway Lights
• HIRL — High Intensity Runway Lights
• REIL — Runway End Identifier Lights (flashing strobes at the approach end)
• PAPI — Precision Approach Path Indicator (four-light visual glideslope)
• VASI — Visual Approach Slope Indicator

If the entry says something like “ACTIVATE MIRL Rwy 18/36” followed by a frequency, the lights are pilot controlled. You key your mic on that frequency: 7 clicks for high intensity, 5 for medium, 3 for low. Brief yourself on this before you’re anywhere near the pattern. Fumbling with activation frequencies while setting up to land at an unfamiliar airport in fading light is a recipe for trouble.

What Should I Look for in the Runway Information?

Beyond the obvious length, width, and surface type, watch for two details that catch pilots off guard.

Displaced thresholds. A displaced threshold means part of the runway is available for taxi and takeoff but not for landing. A runway listed at 5,000 feet with a 400-foot displaced threshold gives you only 4,600 feet of available landing distance. That distinction matters at short fields.

Runway gradient. A sloped runway plays tricks on your visual picture during the flare. An uphill-sloping runway can make it look like you’re too high on approach even when you’re not, tempting you to duck under the glidepath. Knowing about the gradient ahead of time lets you trust your instruments and glideslope indicators instead of chasing an optical illusion.

How Do I Use the Communications Section Effectively?

The communications section lists every frequency you’ll need: ATIS, approach/departure control, tower, ground, and CTAF. Write these on your nav log in the order you’ll use them before you leave the ground. Having them on your kneeboard means you’re not scrolling through menus when you should be looking outside.

One detail students commonly miss: tower operating hours. Some towers are part-time — open from 0700 to 2100 local, for example. If you arrive after the tower closes, the airport reverts to nontowered operations and you need the CTAF, not the tower frequency. The Chart Supplement tells you this. If you don’t check, you could be calling a frequency that nobody is monitoring.

Why Is the Remarks Section the Most Important Part?

The remarks section is free-form text containing airport-specific information that doesn’t fit anywhere else — and it’s where the most critical operational details hide.

This is where you’ll find noise abatement procedures, nonstandard traffic patterns (right traffic instead of the standard left), parachute jumping activity, and wildlife hazards. Notes like “Deer on and in vicinity of runway” appear in the Chart Supplement because the problem is common enough to warrant an official FAA mention.

You’ll also find information about obstructions — trees on the approach end, radio towers off the departure end, ridgelines near traffic pattern altitude. Local pilots know these instinctively. As a visitor, you have no way of knowing unless you read the remarks. A right-traffic requirement due to terrain that rises within 300 feet of pattern altitude is exactly the kind of information that prevents you from flying a downwind leg uncomfortably close to a ridge.

What’s the Best Workflow for Using the Chart Supplement?

Here’s a five-step process that takes roughly five minutes per airport and covers everything you need:

1. Check the field elevation. Set your expectations for performance and density altitude.
2. Review the runway information. Length, width, surface, displaced thresholds, gradients. Confirm the runway is adequate for your aircraft with a margin of safety.
3. Copy the communication frequencies onto your nav log in the order you’ll use them — ATIS first, then approach, then tower or CTAF.
4. Read every line of the remarks. This is where the surprises are, and in aviation, surprises are what we eliminate through planning.
5. Check hours of operation for services you need — fuel availability, tower hours, FBO or self-serve only.

Apply this process to your destination and to divert airports along your route. Evaluating whether an alternate has adequate runway length, fuel, and manageable hazards before you leave the ground turns a potential emergency into a manageable decision.

How Does This Come Up on the Checkride?

During the planning portion of the practical test, your Designated Pilot Examiner will ask about your destination airport. They want to hear more than just the GPS direct course and the weather. They expect you to discuss the runway, the traffic pattern direction, the communication frequencies, the field elevation, and any hazards noted in the remarks. The Chart Supplement is listed as a required planning resource in the Airman Certification Standards under navigation and flight planning.

A Practical Exercise You Can Do Today

Pull up the Chart Supplement entry for your home airport — the field you fly out of regularly — and read it completely. You’ll almost certainly find something you didn’t know: a noise abatement procedure, an obstruction note, or a detail about the lighting system. Reading a familiar airport’s entry teaches you the format so that reading entries for unfamiliar airports becomes fast and intuitive.

Key Takeaways

• The Chart Supplement is updated every 56 days and covers every public-use airport in the U.S. — it’s far more than a frequency list.
• Field elevation, displaced thresholds, and runway gradient all directly affect your approach planning and aircraft performance.
• Pilot-controlled lighting requires briefing the activation frequency and mic-click sequence before you reach the pattern.
• The remarks section is where critical safety information hides — nonstandard patterns, terrain, obstructions, and wildlife hazards.
• Brief your destination and divert airports using the Chart Supplement before every cross-country flight — it’s a checkride requirement and a real-world safety practice.