Circling Approaches, Minima and Sidestep

A circling approach is a maneuver initiated by the pilot to align the aircraft with a runway for landing when a straight-in landing from an instrument approach is not possible or desirable. There are two cases where this occurs. We have already seen certain approaches where the final approach course is aligned with the runway centerline by an angle greater than 30 degrees. One example of this is the VOR or GPS-A at KVNY.

KVNY VOR or GPS-A
(click to enlarge)

Approach not aligned with the runway -

This is an extreme case where the final approach course perpendicular to the runways. Straight-in landing is clearly not possible. So what to do? After the FAF, descend to the MDA as usual. Upon making visual contact with the runway, and with reasonable certainty that you will be able remain in contact, you are free to maneuver however you deem necessary to circle and align with the landing runway. This is typically a modified visual traffic pattern. You must not descend below the Minimum Descent Altitude until continuously in a position from which a descent to a landing on the intended runway can be made at a normal rate of descent using normal maneuvers. The following basic rules apply:

1. Maneuver the shortest path to the base or downwind leg, as appropriate, considering existing weather conditions. There is no restriction from passing over the airport or other runways.

2. It should be recognized that circling maneuvers may be made while VFR or other flying is in progress at the airport. Standard left turns or specific instruction from the controller for maneuvering must be considered when circling to land.

3. At airports without a control tower, it may be desirable to fly over the airport to observe wind and turn indicators and other traffic which may be on the runway or flying in the vicinity of the airport.

In this example, I would know that normal patterns for Van Nuys 16R are right-hand turns, while left-hand turns are normal for 34L (www.airnav.com is a good source of this information for US airports). If I were landing 16R, it may be best to rollout on the runway centerline, fly the extended centerline south, turn crosswind and then fly a right downwind for 16R. The opposite would hold for 34L. I might also cross the field to fly an upwind leg heading 160 before turning crosswind, but 16L has a left-hand pattern and there might be VFR traffic tooling about. You are protected by ATC from running into other IFR traffic, but not necessarily any VFR that might be around.

Here are a few common patterns that can be used for a circling approach:

Circling patterns -

Pattern "A" can be flown when your final approach course intersects the runway early enough to establish a base leg. If you sight the runway too later to fly pattern "A," you can circle as shown in "B." You can fly pattern "C" if it is desirable to land opposite the direction of the final approach, and the runway is sighted in time for turn to a downwind leg. If the runway is sighted too late for a turn to downwind, you can fly pattern "D." Regardless of the pattern flown, you must maneuver the aircraft so as to remain within the designated circling area.

Circling approach area radii

Circling patterns

Based on the aircraft category, you must remain within a certain radius of each runway threshold. While circling, if at any time you lose visual contact with the runway, you must fly a missed approach.

Approach aligned with the runway, but not the one you want to land on -

It is also common to fly to an airport where there is, let's say, an ILS approach but only to one runway. Suppose the winds don't favor that runway on this particular day. What to do? How about flying the ILS down to circling minimums, then circle to land on the opposite runway. Consider Oxnard ILS 25. No ILS exists for runway 7 and you don't have an IFR certified GPS. You should fly the ILS 25 down to 500 feet. If you have visual contact, circle to land runway 07, maybe flying a pattern "C" shown above. Check the minimums on ATIS before attempting the approach. If the wx is less than OVC005, (e.g. OVC003 and winds are 090 at 20), probably should just divert to your alternate. This weather situation says that minimums are probably ok for an ILS approach down to DH (250 feet) but note the circling minimums on the profile view below. Straight-in ILS says DH of 250, but when circling you can only descend to an altitude of 500 feet. With OVC003 it is unlikely you will have visual contact. Got it?

KOXR ILS 25 Profile View - Minimums

Let's look at those minimums for a minute. There is a column for each aircraft category A, B, C and D. More on that in a minute. Notice for S-ILS 25 (straight-in ILS) the Decision Height is 250 (Decision Altitude 290 feet) for all categories. If landing runway 25, you can descend to 290 before going missed if the runway (or other required visual cues) are not in sight.

S-LOC 25 refers to a straight-in for 25 Localizer only. In other words, if the glideslope is out of service. In that case you would remain above 3400 until NELLY, 2000 until PARDS and then stop at 460 (category A or B). If you are circling, in other words not landing runway 25, you stop at 500 feet.

What about those aircraft categories? They are based on your aircraft's Vso or stall speed. In particular, 1.3 times the Vso. Find your aircraft's 1.3 Vso in the chart below and that's your category. Use that column on the IAP minima table to find your DH or MDA. While circling, stay within the area defined by circles centered on the runway thresholds with a radius as shown in the table.

If it is necessary to manuever at a speed higher than your approach category, then use the minimums for the category corresponding to the approach speed you are flying.

CategoryManeuver SpeedCircling Radii
A0 - 90 knots1.3 miles
B91 - 120 knots1.5 miles
C121 - 140 knots1.7 miles
D141 - 165 knots2.3 miles
E166 knots or more4.5 miles

Sidestep Maneuver -

ATC may authorize a side-step maneuver to either one of two parallel runways that are separated by 1,200 feet or less, followed by a straight-in landing on the adjacent runway. Aircraft executing a side-step maneuver will be cleared for a specified nonprecision approach and landing on the adjacent parallel runway. For example, "Cleared ILS runway 7 left approach, side-step to runway 7 right." Pilots are expected to commence the side-step maneuver as soon as possible after the runway or runway environment is in sight. Landing minimums to the adjacent runway will be based on nonprecision criteria and therefore higher than the precision minimums to the primary runway, but will normally be lower than the published circling minimums. However, when in doubt, use circling minimums.


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