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We've all seen circling minimums published on regular approach charts. But have you ever flown an approach that wasn't designated to any particular runway, and has nothing but circling minimums published?

Here's what you should know about circling-only approaches...

What's Up With The Letters?

According to the FAA, "approaches that do not have straight-in landing minimums are identified by the type of approach followed by a letter." The first circling-only approach published for an airport is labeled with the letter "A." Lettering for subsequent approaches published continues in alphabetical order.

In the example we'll use today, the Molokai Airport in Hawaii (PHMK) has both a "VOR or TACAN-A" and an "RNAV (GPS)-B." They're both approaches to the same airport, from a similar direction, yet neither is designated for a specific runway. There are no straight-in approaches available at Molokai.

Reasons Why Circling-Only Approaches Are Published

There are a few reasons why an approach will be published as circling-only:.

• The final approach course alignment with the runway centerline exceeds 30 degrees.
• The descent gradient is greater than 400 ft/NM from the FAF to the threshold crossing height (TCH). When this maximum gradient is exceeded, the circling only approach procedure may be designed to meet the gradient criteria limits. This does not preclude a straight-in landing if a normal descent and landing can be made in accordance with the applicable CFRs.
• A runway is not clearly defined on the airfield.

Flying The "Pattern"

Keep your circling approaches as similar to a traffic pattern as possible, and don't descend too early if you're flying below traffic pattern altitude.

If the ceilings are high enough and the visibility is good enough, it's not a bad 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.

Depending on how you approach the airport, you might not align perfectly with a "normal" pattern leg. This is why it's so important you plan how to fly the pattern BEFORE you initiate the approach. Do this, and you'll set yourself up for a smooth, safe landing every time.

On any circling approach, you're guaranteed at least 300 feet of obstacle clearance within the protected area. And with approaches developed or revised after 2012, the protected area has been expanded. Stay within this area, and it doesn't technically matter how you fly to the runway. You'll stay safely clear of terrain and obstructions. Here's what the protected area looks like for new or revised approaches:

Click here for more information on circling minimums, distances, and how to know if your approach has the new or old criteria.

Example: Molokai Airport, Hawaii

Let's take a look at the VOR-A into Molokai, Hawaii (PHMK). As we mentioned earlier, this airport only has circling approaches. There are no straight-in approaches to any of the runways available. The VOR-A approach from the West most closely aligns with Runway 5, and at first glance, you might wonder why this isn't published as a VOR approach to Runway 5.

Past the FAF, there's a crossing restriction at the fix "WUBAL," which you must cross at or above 1,940 feet. This crossing is mandatory on the approach unless you can descend visually and maintain your own obstacle/terrain separation.

Since this approach isn't charted for Runway 5, there isn't a descent angle published. So let's look at why a straight-in approach, crossing WUBAL at 1,940 feet, is unrealistic.

A little math is required, but it's still pretty straight forward. From WUBAL to MAVGN, you need to lose about 1,500 feet. We'll round WUBAL to 2,000 feet and MAVGN (the MAP, closely matching the runway threshold) to 500 feet, or airport elevation. (2,000-500=1,500 feet to lose).

You'd have 1.4NM to accomplish the descent. If you round that to 1.5NM to make the math a little easier, you'll need to descend at 1,000 feet per nautical mile (1500/1.5=1,000).

Going back to the 1 In 60 Rule, that means you'll need to pitch down 10 degrees (1,000 FPNM/100) to accomplish the descent.

That's way too steep for a stable approach in most aircraft. If you're backing up the descent with your VSI, at 90 knots (1.5 Miles Per Minute), you'd need about a 1,500 Foot Per Minute (FPM) descent rate (10 degrees X 1.5 MPM X 100 = 1,500 FPM). At 120 knots, you would need to descend 2,000 FPM.

See why that doesn't work? There's a reason you can't descend straight-in on this approach. Instead of trying to descend straight in, join the traffic pattern and flying a normal, stable approach with your standard power settings and descent rates.

Where have you flown a circling approach like this? Tell us about your experience in the comments below.

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