Chris, an AviationChatter reader asked a great question about holding patterns:

I understand the hold entry, but what is killing me is trying to determine the “mental picture” of the actual racetrack when ATC says “Hold south on the 180 radial.” My heading is 155º in this example.

What does ATC saying “south” have to do with anything?

Well Chris, the compass direction “south” doesn’t have much to do with your holding pattern at all. It’s just extra language to clarify the hold and help you, the pilot, visualize the proper holding pattern.

So, what does “hold south” have to do with our holding pattern? Simple answer: the inbound and outbound legs (that is, the majority of the holding pattern) must be south of the holding fix.

Suppose you are entering a standard holding pattern on the 180º radial. That means you are flying 360º inbound legs. And let’s keep this nice and simple by supposing that you are on a 360º heading.

Look at the image to the right. Notice that most of the holding pattern is located to the south of the fix? Our friendly air traffic controllers might have issued this clearance by stating “Hold south of the BNA 180º radial.” Then again, they may have simply asked you to “Hold on the 180º radial.”

So Why Explicitly State the Compass Direction?

Our friends in ATC will usually provide a compass direction to prevent confusion between radials and inbound legs. Heres’s a common mistake. The pilot reads back instructions to hold on the 180º radial, but fails to realize that the 180º radial extends from the station. Instead of flying a 360º inbound leg, the pilot spins the CDI to a course of 180º.

This changes everything. The airplane flying the wrong way and well out of the “safe side” of the holding pattern! Notice that the holding pattern is on the north side of the hold and requires a parallel entry. Had ATC asked the pilot to “hold south,” our unfortunate aviator might have realized his error.

Back to the question

So back to your question, if ATC asked you to “hold south on the 180º radial” and you are flying a heading of 155º, you should fly a teardrop entry to the holding pattern pictured on the right.

Notice that I am assuming standard right turns as ATC did not specify a direction.

I generated a few more examples to clarify things below.

"Hold east of the 090º radial, left turns"

"Hold northeast of the 045º radial."

"Hold southwest of the 225º radial"

I created all these images with Hold Here, an iPhone app that computes holding pattern entries and bugout times.

Without taking fuel burn into consideration, you can wind up in a situation where you no longer have enough fuel to fly to the alternate – and perhaps even the destination.As an instrument rated pilot, you know all about flying holding patterns and computing entries. But you can’t fly around in a holding pattern all day, sooner or later you’ll have to decide when to bug out and go to the alternate. It’s better to make this decision sooner than later, here’s how.

The fundamental problem with holding patterns is fuel. Here you are burning gas, but getting no closer to the airport. Without taking fuel burn into consideration, you can wind up in a situation where you no longer have enough fuel to fly to the alternate – and perhaps even the destination.

We need to put first things first: always fly the airplane. This is especially important in single pilot IFR with no autopilot. You don’t want your fuel planning to distract you from making a safe holding pattern entry or worse.

Determining your bug out time is as simple as 1, 2, 3.

1. Plan the diversion from the holding fix to the alternate airport.

This one should be easy – you were trained for it as a private pilot. Find a radio navigation As a pilot, you should feel uneasy about landing with anything less than your required reserve fuel, (45 minutes for IFR flight). That’s why I suggest planning to divert just before your fuel on board equals BURN + Reserveaid and course that will get you  to that alternate. You will also need to figure out the  distance to the alternate. All of this is almost automatic with the use of modern GPS systems, which typically provide a heading and distance at the very least.

2. Get the fuel burn to the alternate.

You might think that you’ve already done this in the preflight planning phase, but be careful. The alternate airport fuel burn on your flight plan is probably based on flying from the destination to the alternate. Alternate fuel burn will be different from the holding fix and this is especially critical if the alternate airport is beyond the destination.

"Captain, this primitive flight computer is most illogical"

Since most private pilots think of fuel on board in terms of minutes, this is actually pretty simple. Just spin the E6B flight computer (or cheat by looking at your GPS) and figure out the time from the holding fix to the alternate.

We’ll refer to this as BURN in step 3.

3. Figure out the bug out time.

As a pilot, you should feel uneasy about landing with anything less than your required reserve fuel, (45 minutes for IFR flight). That’s why I suggest planning to divert just before your fuel on board equals BURN + Reserve.

This sets us up to land with 45 minutes of gas in the tank at the alternate airport.

Continue to page two for an example ->

I’m sure all of you IFR types know the drill. ATC assigns you a holding pattern and it is up to you to enter that hold in one of three ways: parallel, direct, or teardrop. Which entry do you choose? Well it all depends upon your intercept angle with the holding pattern… or something like that. Truth be told, I have no idea! But wait, how can you fly a holding pattern if you can’t do the mental math to compute your entry? It’s quite simple really: I do it visually.

Holding Pattern

That’s right, I barely even think about my entry. I just visualize the holding pattern, look at it, and visualize the appropriate entry. It’s quite simple really, lets look at a typical holding pattern. There are three possible holding pattern entries, all of which depend on where our airplane will be after crossing the holding fix. The trick is to remember three simple rules; after passing the fix, if the airplane is:

1. Inside the hold, perform a teardrop entry.
   Given the hold in the picture, if we approach the holding fix from the Northwest, then our airplane will be inside of the holding pattern (between the inbound and outbound legs).
2. Outside the hold, perform a parallel entry.
   Again, look at the picture, if we arrive from the East, the airplane will be outside of the holding pattern. We must turn to our outbound heading (180 in this case) and begin a parallel entry.
3. With the hold, perform a direct entry.
   This is the no-brainer. If you are heading in the same general direction as the inbound leg, just make that initial (in this case right) turn and fly the outbound leg.

This method sure beats doing a bunch of mental math whilst flying an airplane, and seriously reduces the chance of error. It is worth nothing that air traffic controllers don’t really care what kind of entry you make, so long as the airplane remains on the safe side (that’s the same side as the outbound leg). If you get all garbled up, just stick to the safe side and make it work!

I know holding patterns are a very abstract concept and can be difficult to envision. Please comment on this post if you need clarification on visually computing holding pattern entries.