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Circling approaches aren't limited to non-precision approaches. Do you know how to use a glideslope to help your circling 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.
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 20 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 allowed 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.
This approach will easily descend you below the clouds for your circle.
Unless the notes section or NOTAMs say otherwise, there are no restrictions 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.
Here's the scenario: You're flying an autopilot-coupled glideslope to the circling MDA.
Do you see any potential issues?
Even with the MDA altitude bugged on your flight instruments, the autopilot will fly through the MDA and continue down the glideslope. It will not level off at your preselected altitude. This is why you 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 300-400 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.
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.
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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