Approach Chart Symbols You Think You Know But Might Not

A recent Boldmethod quiz on a single approach chart symbol exposed a consistent gap in instrument pilot knowledge: most pilots can execute approach procedures by pattern recognition but struggle to define the symbols in words. That gap is where edge cases hide. This is a top-to-bottom walkthrough of the symbols on an instrument approach procedure chart that carry the most operational weight.

Two Briefing Strip Symbols Most Pilots Gloss Over

The briefing strip - the row of information at the top of every IAP chart - contains two small symbols that have real preflight consequences.

The letter T inside a triangle means takeoff minimums are not standard at this airport. The standard minimums are 1 statute mile visibility for single and twin-engine aircraft, and ½ statute mile for multi-engine turbines. A T-in-a-triangle means those numbers don’t apply here - either higher visibility is required, or a specific departure procedure exists to clear terrain or obstacles. The actual requirement is published in the instrument approach procedure volume under departure procedures.

This is a preflight item. If you plan to depart an airport with that symbol and haven’t looked up the departure procedure, you are not fully prepared. In IMC, the terrain is still there regardless.

The letter A inside a circle means alternate minimums are not standard. Under IFR flight planning rules, the standard alternate minimums are 600-foot ceiling and 2 statute miles visibility for precision approaches, and 800 and 2 for non-precision. When a potential alternate airport carries a circled A on its charts, those numbers don’t apply - the actual alternate minimums are published separately and may be significantly higher.

The common failure point: a pilot files an alternate assuming the 600-and-2 standard applies, the actual alternate minimum is 1,500-foot ceiling, and the weather at that alternate deteriorates en route. The circled A is a flag. It means look it up before filing.

What the MSA Circle Actually Tells You

The plan view - the bird’s-eye overview of the approach environment - typically includes a circle with compass bearings and altitudes marked around it. This is the Minimum Safe Altitude (MSA) circle.

The MSA guarantees 1,000 feet of obstacle clearance within 25 nautical miles of the navigation facility or reference fix at the center. When the circle is divided into sectors, terrain varies enough in different directions to require different floors per quadrant.

The MSA is not a minimum IFR enroute altitude. It’s not an approach altitude. It is an emergency reference - a backstop for lost clearances, lost communications, or any situation requiring a known safe floor while sorting out a problem.

Also in the plan view: obstacle and terrain symbols. Black dots and triangles with numbers represent spot elevations and obstructions, with the highest feature in the approach area typically called out specifically. These are what the approach designers accounted for when establishing Minimum Descent Altitudes and missed approach altitudes. When an MDA looks high relative to airport elevation, the reason is usually visible in the plan view.

The Final Approach Fix: The Descent Trigger on Non-Precision Approaches

The profile view is where most procedural information lives and where the most commonly misunderstood symbols appear.

On a non-precision approach, the transition from the intermediate segment to the final approach segment is marked by a four-pointed maltese cross in the profile view. Crossing that symbol inbound authorizes descent toward the Minimum Descent Altitude (MDA). If timing is being used to identify the missed approach point, the approach clock starts here. The maltese cross is the trigger.

On a precision approach (ILS), the glideslope intercept altitude serves the same functional purpose, and descent is continuous along the glideslope rather than fix-triggered. A maltese cross may still appear on ILS charts at the outer marker or equivalent fix, but execution is glideslope-driven.

Miss the FAF symbol on a non-precision approach and an early descent is possible - directly into an intermediate altitude that exists for obstacle clearance.

Step-Down Fixes: Why They Exist

Inside the final approach segment on some non-precision approaches, one or more altitude shelves appear between the FAF and the runway environment. These are step-down fixes, shown as a horizontal line with a fix identifier and minimum crossing altitude.

The logic: an obstacle between the FAF and the runway prevents authorizing a continuous descent to MDA immediately after the FAF. A fix is established at the point where the aircraft can verify position, and a lower altitude is authorized beyond it.

Skipping a step-down fix means the aircraft may be 200 to 300 feet below a protected altitude with something ahead that the approach was designed to clear. These aren’t procedural formalities - they exist because something specific is there.

The Visual Descent Point

The Visual Descent Point (VDP) is marked as a small V on the profile view. It identifies the latest point from which a normal, stable descent from MDA to the touchdown zone is geometrically possible.

The VDP is advisory, not mandatory. What it communicates is a decision boundary. Flying level at MDA past the VDP without visual contact on the runway means the geometry is now working against a stabilized approach - any subsequent descent requires a steeper angle, a rushed final, and an unstabilized profile. The VDP is the chart indicating that if the runway isn’t in sight at this point, the missed approach should be the active consideration.

Not all non-precision approaches have a VDP. The FAA can only publish one when it can be defined by a fix or distance the aircraft can positively identify.

Timing Tables: A Skill in Decline

On non-precision approaches without DME, a timing table provides elapsed time from the FAF to the missed approach point by groundspeed. As an example: at 60 knots, 2 minutes 20 seconds; at 90 knots, 1 minute 30 seconds; at 120 knots, 1 minute 10 seconds.

GPS navigators handle this automatically in modern cockpits, which is why timing proficiency has declined. But if the navigator goes dark on approach, the timing table is still printed on the chart. Cross the FAF, start the clock, fly to MDA, execute the missed approach at the prescribed time if the runway doesn’t appear. It remains valid instrument flying technique.

Understanding RNAV Approach Minimums

RNAV (Area Navigation) is the umbrella term for GPS-based approaches. The minimums section of an RNAV chart contains multiple lines representing different levels of system capability, and the right line depends on the aircraft’s equipment.

LNAV (Lateral Navigation) is the basic GPS approach - no vertical guidance from the navigator. The aircraft flies to an MDA and looks for the runway, identical in concept to a classic non-precision approach.

LNAV/VNAV adds a computed vertical path. It requires either a WAAS receiver or a baro-VNAV capable system. Minimums are typically lower than straight LNAV.

LPV (Localizer Performance with Vertical Guidance) is the best WAAS GPS approach available. LPV approaches use Decision Altitudes rather than MDAs and can reach 200-foot minimums at some airports - equivalent to a Category I ILS. A WAAS-certified receiver is required.

LP (Localizer Performance) uses WAAS lateral accuracy for tighter minimums than LNAV but provides no glidepath.

The RNAV minimums section functions as a capability menu. The navigator typically sequences to the appropriate line automatically, but the pilot should independently verify which line applies to their certified equipment before briefing the approach.

Fly-By vs. Fly-Over Waypoints

This distinction appears as a minor chart detail but carries significant consequences in terrain environments, particularly during missed approaches.

A fly-by waypoint is marked with a plain four-pointed star. The navigator anticipates the turn and begins tracking onto the outbound course before the aircraft physically crosses the fix. This is standard for nearly all enroute waypoints.

A fly-over waypoint is marked with a circle around the star. The aircraft must pass directly over the fix before initiating any turn. Obstacle clearance requires reaching that specific position before maneuvering - turning early would cut a corner and reduce terrain separation.

The most consequential application is on missed approaches. If the initial missed approach turn is at a fly-over waypoint, the aircraft must remain on track until the fix is crossed before beginning the turn. A shortcut turn on a missed approach in a terrain environment is not recoverable.

Aircraft Categories and What the Minimums Boxes Mean

Every minimums section is organized by aircraft category, A through D, based on approach speed at the threshold: 1.3 times the stall speed (Vso) in the landing configuration at maximum certificated landing weight.

• Category A: below 91 knots
• Category B: 91–120 knots
• Category C: 121–140 knots
• Category D: 141–165 knots

If approach speed places an aircraft in a higher category, that category’s minimums apply - not the lower category. Flying faster than your category for any reason requires moving up to the higher category’s minimums.

The minimums section also distinguishes straight-in from circling. Straight-in minimums apply when the final approach course is aligned within 30 degrees of the runway centerline and other criteria are met. Circling minimums are always higher, because circling places the aircraft in a close-in maneuvering environment that requires a wider, higher buffer.

The protected area for circling varies by category - faster aircraft need more room. If visual contact with the runway environment is lost during a circle, the missed approach is immediate and begins from the aircraft’s current position, not from the missed approach point on the chart.

The Missed Approach Symbol

After the missed approach point, the profile view transitions to a dashed line heading upward. The plan view shows the initial track with an arrow - sometimes straight ahead, sometimes an immediate climbing turn, sometimes a track to a navigation fix leading into a holding pattern.

Holding patterns on the plan view appear as a racetrack. The holding fix is identified; the inbound and outbound courses are implied by the racetrack’s orientation.

The initial climbing heading, initial altitude, and first fix or hold should be briefed before the approach begins. The window between executing a missed approach and flying it is not the time to read the chart.

Key Takeaways

• The T-in-a-triangle and circled A on the briefing strip both require specific lookups before flight - standard minimums do not apply, and the consequences of skipping the check are operational, not academic.
• The maltese cross (FAF) on a non-precision approach is the authorized start of descent toward MDA and the reference point for approach timing.
• Step-down fixes and the VDP exist because specific obstacles and geometry demand them - skipping either puts the aircraft below a protected altitude.
• RNAV minimum lines (LNAV, LNAV/VNAV, LPV, LP) represent distinct equipment requirements; the navigator may sequence correctly, but the pilot must independently verify which line applies.
• Fly-over waypoints - identifiable by a circle around the fix star - require crossing the fix before turning. The missed approach is the most critical place this distinction matters.
• The FAA Aeronautical Chart User’s Guide, available free from the FAA, covers every chart symbol with definitions and is worth revisiting after instrument training.