Circling approaches aren't limited to non-precision navigation. Do you know how to use a glideslope to help your circling approach?

Why Would You Circle From An ILS Approach?

Just like a VOR, RNAV, or LOC approach, you can circle to land from an ILS approach using glideslope as a navigation aid. Many ILS approaches contain circling minimums, and they're a great way to get below the clouds in order to land on a more suitable runway.

The Scenario: Gulf Shores, Alabama (KJKA)

Jack Edwards Airport has two intersecting runways, 17/35 and 9/27. You're on an IFR flight and the clouds are overcast at 1,000 feet above the field. Approaching KJKA from the east, only Runway 27 has an ILS approach. With winds steady at 35 knots from the North, you're not going to land on Runway 27 due to personal limits.

Runway 35 is obviously the most favorable runway, with winds nearly straight down centerline. Since it's not nighttime, this circle is perfectly legal according to the chart notes. Looking at the ILS RWY 27 chart below, you'll see that your circling MDA is 480 feet MSL if you can identify the fix GEVBE with DME. This approach will easily descend you below the clouds for your circle.

But First, Is It Legal?

Of course! There's never a restriction on following a functional glideslope when you've been cleared for an ILS approach, as long as you follow circling criteria. And if you have an autopilot, using the glideslope with the autopilot coupled is a great way to reduce your workload, giving you extra "bandwidth" to monitor approach parameters and aircraft performance.

The catch is making sure you don't descend below circling MDA as you reach the bottom of the approach.

Which Autopilot Mode Should You Use?

Here's the scenario: you're flying an autopilot-coupled glideslope to the circling MDA. Do you see any problems?

Even with the MDA altitude bugged on your flight instruments, the autopilot will fly through the MDA and continue on the glideslope. It will not level off at your preselected altitude. This is why typically don't "bug" minimums in the altitude preselect of an ILS approach. If you're not paying close attention, you could easily fly right through the circling MDA and get too low. So, what can you do instead?

No later than 100-200 feet before reaching MDA, select the autopilot's vertical speed mode (VS). Track the indicated glideslope with VS mode. This flight mode will allow the autopilot to level off at your circling MDA.

Story short, before you begin an approach, brief which modes you'll use and think through how they'll react to altitude capturing. If your autopilot is in approach mode with the glideslope coupled, it won't level off at a preselected altitude.

Fly A Standard Circling Approach

As you level off at circling MDA, you must remain on the LOC final approach course until you're within the "protected area," which is a distance value from runway edges. The protected areas for the "new" expanded circling minimums use a connection of arcs from the end of each runway (KJKA has expanded circling minimums). The minimum distances account for the impact of wind on a circle, bank angle limits, and higher true airspeeds at high altitude airports. So overall, they give you a high margin of safety.

Exception 1: Wider Turns

• If you can visually clear yourself from obstacles and terrain, you do not have to follow the circling criteria minimum distances.

Exception 2: Staying Higher

• If the ceilings are high enough and the visibility is good enough, it's a good idea to level off at pattern altitude instead of going all the way down to circling MDA. It gives you familiar descent points and power settings, and it keeps your approach to landing as normal as possible.

Here's a chart explaining the protected area distances that apply to you during your circle:

After leveling off at MDA, fly the circling approach as you normally would. Click here to learn everything you need to know about flying circling approaches.

Use The Acronym "CAMI" Make Sure You Don't Get Low

Many airlines recommend the use of the acronym "CAMI" for flying instrument approaches. This scenario is the perfect example of using CAMI to your benefit. If you're not monitoring the autopilot approach modes carefully, and you're not ready to intervene, you could descend through MDA without even realizing it.

Have you ever circled off an ILS approach? Tell us how you would handle this situation in the comments below.

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