What is the difference between straight-in and circling minimums on an instrument approach?

Straight-in minimums apply when the final approach course is aligned within 30 degrees of the runway centerline and a normal descent from the minimum altitude to the runway is possible, allowing you to land without maneuvering. Circling minimums apply when those alignment or descent criteria are not met, requiring you to maneuver the aircraft visually around the airport to align with the landing runway. Because circling requires you to fly a visual pattern at low altitude around the airport environment, the minimums are almost always higher than straight-in minimums to ensure obstacle clearance over a wider area.

How do aircraft categories affect circling minimums and the protected maneuvering area?

The FAA assigns aircraft to approach categories (A through E) based on 1.3 times the aircraft's stall speed in the landing configuration, and each category has a different obstacle clearance radius measured from each runway threshold. Higher, faster categories require larger protected areas and therefore typically have higher circling minimums to maintain at least 300 feet of obstacle clearance within that radius. Pilots must circle at or above the published circling MDA for their aircraft category and must not descend below it until in a position to make a normal landing on the intended runway.

Why would an approach chart publish only circling minimums and not straight-in minimums?

An instrument approach procedure will not be authorized for straight-in minimums if the final approach course is offset more than 30 degrees from the runway centerline, or if the descent gradient required to reach the runway from the minimum descent altitude would be excessively steep. In those situations, the FAA publishes only circling minimums because a straight-in landing cannot be safely accomplished without an abnormal maneuver or excessive descent rate. Pilots flying such an approach must always plan to circle to land and must remain visual within the circling obstacle clearance area until established on a normal final approach.

Straight-In vs Circling Minimums Criteria

Every instrument approach chart lists one or more sets of minimums — the lowest altitude and visibility a pilot may use to descend toward a runway. At first glance the table of numbers at the bottom of the chart can feel overwhelming, but two fundamental categories organize everything: straight-in minimums and circling minimums. Understanding why these two sets exist, how they are calculated, and when you must use one versus the other is essential knowledge for every instrument-rated pilot — and a reliably tested subject on the FAA Instrument Rating knowledge exam.

The core distinction is geometric: straight-in minimums assume the aircraft will land on a specific runway in roughly the same direction it flew the final approach course. Circling minimums assume the aircraft must maneuver visually after reaching the minimum altitude, because the runway it will land on is oriented differently from the final approach course. That maneuvering requires the aircraft to remain lower and slower while turning, so the obstacle clearance area must be much larger — and the minimum altitude must accommodate every obstacle in that larger area, making circling minimums almost universally higher than straight-in minimums for the same approach.

What Makes an Approach Straight-In?

The FAA establishes straight-in minimums only when the final approach course meets specific alignment and vertical descent criteria. According to the Instrument Procedures Handbook (FAA-H-8083-16), an approach qualifies for straight-in minimums when the angle between the final approach course and the runway centerline does not exceed 30 degrees. This ensures that when the runway becomes visible, the pilot can continue in roughly the same direction rather than making a sharp turn at low altitude.

A second criterion involves the vertical descent angle. If the approach requires an excessively steep or awkward descent to reach the runway threshold — generally if a normal straight-in descent would require landing too far down the runway — the procedure designer may omit straight-in minimums entirely even if the course alignment is within 30 degrees. In that case the chart will show only circling minimums. You will recognize this situation when the minimums section of the chart does not list a specific runway designation under the straight-in column; the approach is named something like "VOR-A" or "RNAV-B," indicating circling-only minimums.

When straight-in minimums exist, they are tied to a specific runway — for example, "ILS RWY 28" or "RNAV (GPS) RWY 10." The published decision altitude (DA) for precision approaches or minimum descent altitude (MDA) for non-precision approaches applies only to that specific runway and that direction of landing.

Circling Minimums: A Protected Maneuvering Area

Circling minimums apply whenever the pilot must maneuver visually after completing the instrument portion of the approach. The circling maneuver could be a simple S-turn to align with the opposite runway end, or a full overhead pattern when the approach delivers the aircraft abeam or perpendicular to the intended landing runway.

The FAA protects the circling area by drawing arcs of a specific radius from each runway threshold. Aircraft must remain within these radii while circling. Critically, the radii are categorized by aircraft approach category, which is determined by 1.3 times the aircraft's stall speed in the landing configuration at maximum certified landing weight (1.3 × Vso). The categories and their expanded obstacle-clearance radii are:

Category A (91 knots or less): 1.3 nautical miles
Category B (91–120 knots): 1.5 nautical miles
Category C (121–140 knots): 1.7 nautical miles
Category D (141–165 knots): 2.3 nautical miles
Category E (166 knots or above): 4.5 nautical miles

It is worth noting that in 2012 the FAA began expanding circling approach protected areas using a new methodology that generates larger, more realistic arcs based on bank angle and airspeed, rather than the older fixed-radius circles above. Approaches designed or redesigned under this new standard are identified with the notation "Expanded Circling Approach Area" on the chart. Regardless of methodology, the principle remains the same: a minimum circling altitude (MCA) is published to ensure at least 300 feet of obstacle clearance within the protected area for Category A and B aircraft, and at least 300 feet for higher categories within their respective radii. This 300-foot buffer is a critical exam number.

Reading the Minimums Box

On a standard U.S. approach chart, the minimums section is organized in columns by aircraft category (A, B, C, D) and rows by type of approach (straight-in, circling). Straight-in minimums appear first, labeled with the specific runway (e.g., "S-ILS 28" for a straight-in ILS to Runway 28). Circling minimums appear below, labeled simply "CIRCLING."

Each box contains an altitude and a visibility requirement. For precision approaches the altitude is a Decision Altitude (DA) — you must decide to land or execute a missed approach at that exact altitude. For non-precision straight-in approaches and all circling approaches the altitude is a Minimum Descent Altitude (MDA) — you descend to the MDA and level off, continuing only if the runway environment is in sight and a normal landing can be made. You may not descend below the MDA while circling. If you lose visual contact during the circling maneuver, you must immediately execute the missed approach procedure, initially climbing and turning toward the runway from which the instrument approach was made.

Why Circling Minimums Are Almost Always Higher

Because the circling area is so much larger than the narrow corridor protected for a straight-in approach, it inevitably encompasses more terrain, obstacles, and structures. A ridge that sits safely off to one side of the final approach course may lie squarely within the circling area. The minimum circling altitude must clear all of those obstacles within the applicable radius. Additionally, a pilot circling at low altitude in IMC-adjacent conditions — perhaps with a broken ceiling just above the MDA — is in a higher-workload, higher-risk situation than one flying a stabilized straight-in approach. The higher minimums reflect both the obstacle geometry and the operational risk.

There is also an important relationship between the circling MDA and visibility. The visibility minimum for circling is typically higher than for straight-in, because the pilot needs to maintain visual contact throughout the maneuver. Losing sight of the runway while turning base-to-final at 500 feet AGL over mountainous terrain is an extremely dangerous situation.

Key Numbers and Rules

30-degree rule: The final approach course must be within 30 degrees of the runway heading to qualify for straight-in minimums.
300 feet: Minimum obstacle clearance within the circling protected area.
Aircraft approach category is based on 1.3 × Vso at maximum landing weight — this determines which column of minimums you use.
You may not use a lower category's minimums unless you operate the aircraft at that category's airspeeds throughout the approach and landing.
You may voluntarily use a higher category's minimums if you choose to fly at higher approach speeds, which may be operationally necessary in some aircraft.
Circling is not permitted in some cases — certain approaches note "Circling NA" for specific sectors or entirely, due to terrain or airspace. Always check.
Lost visual contact during circling: Execute the missed approach immediately; turn toward the runway used for the instrument approach as a starting point.

Memory Aid

For the straight-in alignment rule, remember: "30 or more, go around the floor" — if the offset is 30 degrees or more, you lose straight-in minimums and must use circling minimums (the "floor" being the higher circling MDA). This is a student-invented mnemonic but it captures the exact threshold neatly.

Common Test Traps

Confusing DA with MDA for circling: Circling minimums are always MDAs, never DAs. You level off at the MDA and maintain it while maneuvering — you do not descend further once you break out visually.
Using the wrong aircraft category: Your category is fixed by 1.3 × Vso. You cannot simply choose Category A to get lower minimums if your aircraft's approach speed places it in Category B. The examiner will test this directly.
Assuming a straight-in must exist: If an approach is named with a letter suffix (VOR-A, RNAV-B) instead of a runway number, it means no straight-in minimums exist — circling only.
Forgetting the missed approach direction after losing sight while circling: You must maneuver toward the runway used for the instrument approach before following the published missed approach procedure — not just climb straight ahead.
Overlooking "Circling NA" notes: Some charts prohibit circling in certain sectors or entirely. Pilots who do not read these notes may plan an approach that legally cannot be used for the intended landing runway.