Approach Tips | The Zipper Method

The Zipper Method

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Greetings, ladies and gentlemen. Today’s post is intended to inform you all of a method approach controllers use when conducting approaches for aircraft into an airport. Broken into three distinct techniques, the “zipper method” is a great way to increase airport capacity and amount of aircraft handled. Below are some infographics and captionings to explain the concepts presented. Cheers!

  • Disclaimer: altitudes, speeds, and downwind widths are theoretical concepts and not representative of actual commands an controller might give, not to be taken with a grain of salt.

Basic Zipper Example

  • This is what you will often see when we split up our approach paths. Instead of all planes following one downwind, multiple aircraft are divided into two downwinds. Depending on the airport, there are a number of different techniques an approach controller can use to achieve maximum arrival efficiency for aircraft.

Technique #1- The Manual Zip

  • At its most basic form, the zipper method consists of turning one plane’s base at a time, as demonstrated in the picture above. One runway airports such as San Diego benefit greatly from this.
  • Although effective in modest traffic, following this technique based on vectoring alone has one drawback- lengthening the final approach line. You can tell from the arrows that each subsequent plane has to go further and further out.
    • If all planes approach the final base turn at the same time and same speed, the controller would be required to send the second, third, fourth plane, etc, further out to build some spacing.
  • The problems of this method can be solved with two simple solutions, depending on the type of runways available at the destination airport.

Technique #2- Speedy Zip

  • As you can see here, the planes on right downwind to the runway have been assigned 180 knots IAS. The planes on left downwind are at 220.
  • This type of method used in the zip allows the planes on left downwind to reach the base turn first, turning onto final before the planes on right downwind approach their turning point.
    • Of course, slowing to final approach speed withstanding.
  • This solves the issue of having to lengthen the approach line significantly, allowing for a true “zip,” turning one plane in after another consistently and seamlessly.

Technique #3- Parallel/Alternating Zips

  • In this specific example, we have planes on both downwinds turning to Atlanta airport. Due to the multitude of parallel runways at the airport, it’s simply a matter of having both planes turn base when appropriate without worrying about them stacking on the same runway.
  • One problem, however. With the “zip” concept putting both planes on the final turn so close to each other, separation has to be made.
    • Therefore… the solution is to send one of the two aircraft at a lower altitude.
    • 1,000 feet MINIMUM!
  • The reasoning for this is to prevent both planes from colliding with each other if they fail to intercept and line up with the localizer at an appropriate time. Which, to be quite frank, happens to 70% of planes most of the time. Hence, it being a must.
  • Essentially, you’ve killed two birds with one stone, making a double zip. You’ve increased your capability by twice as much and can funnel aircraft in on a rapid-fire basis.

What do you take away?

Hopefully, you may better understand why a controller is utilizing one of the techniques listed above while flying your aircraft. And, perhaps, if you control on occasion, you may find the information useful in creating a zipper method of your own.

Although there are even more techniques developed by our outstanding controllers, those are some of the most common, tried-and-true ones you will find. Try to work off a solid foundation of what you are given, and then add your own modifications on top of that. Everyone is different with how they control!

  • Further disclaimer: Yes, I know. The name. But there’s really no better way than to call it the zipper method.
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Thanks for the info! I hope that I can incorporate this into my controlling!

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Thank you for the explanation!
It helps me appreciate more of how much efforts you guys are making in making my approaches n landings seemingly uneventful.
Thank you🛬👍🏼🛫

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The amount of thought and effort an approach controller has to put in is amazing.

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Excellent post Josh. Thanks for the tutorial

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This is the biggest thing to remember. Also if you looked at the plates for parallel runways, most of the time the two intercepts would be at different altitudes by design.

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@JoshFly8. MaxSez: Interesting Approach Procedure this “Zipper Method”! I looked for it or something similar in the AIM and a few other reliable sources but was unable to locate it in “Standard Practice” notation, reference or FAA guidance. It appeared with this method close coordination with “Tower” is a requisite. Seems to me utilizing Holding Stacks would solve the speed/altitude/downwind separation problem associated. It’s like juggling, to many balls in the air during high tempo ops leads to a loss of situational awareness. Great Tutorial for those willing to employ this method.
Regards.

Note: DOT’s in some states uses a “Zipper” method for vehicular traffic control at Crash/Construction sites. Left/Right Merge in multi lane hways. It was the only search record associated with the term “Zipper Method”… if there is a primary aviation source for this technique pls post it)

There aren’t going to be many techniques posted about. Most of what you’ll find are the concrete rules and patterns for towers.

These are techniques, just like 5 n 2’s and 6 n 1’s when controlling aircraft in a pattern. You won’t find this stuff posted as an FAA or local procedure because all you’re required to follow are the separation guidelines. How you bring aircraft into the field as a controller is up to you, unless there are specific facility OI’s stating other wise. Somewhere that comes to mind that dictates the arrival controllers would use is ATL, JFK, LAX and your high level approach controls.

Outside of the minima rules, it’s free reign in deciding how to safely and expeditiously move aircraft.

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@THE-OP… MaxSez. Interesting observation. Do you consider SID/STAR. “Minima” When IFR?

No, but I can pull you off that arrival or SID at any time.

Very few airports actually have these procedures when considered. These procedures just reduce the controller workload as I know what you’ve been instructed to do and don’t need to issue you any instructions unless I see a deviation, turn or incorrect altitude.

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If you are flying these you are IFR. A VFR aircraft will not be flying these as they require instruments

@THE-OP. MaxSez: Please don’t suggest I’m ignorant on the rule of the road, type was not a consideration in this discussion. I did’nt even point out the down wind approach as depicted which I’ll leave for another time. Let’s not play the mines bigger than yours game here. I’m moving on, I stand by my comment. G’day

I’m not sure where that got lost in translation. Didn’t know if you meant IFR as in weather or type of flight. Just clearing any misconception…

@THE-OP… MaxSez: “Appears we have a failure to communicate, Cool Hand”… if I meant Wx I had utilized the term IMC. Anyway, the IF procedure advertised could work for a real savvy IFATC Artiest. I’m old school I fly by the AIM and in my experience here have always been vectored to the IP FIX up wind. Different strokes, I call the procedure an IF crap shoot on a high tempo day.

Always a pleasure Op when “They” bring in the Big Guns. We’ll have to discuss this over a beer sometime, cuss and discuss the benefits of Holds v Vectors/Well executed Flt Plans etc.
Cheers Shipmate, I’m out of here…

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I can not wait for the hold function to operate correctly. I love using that and dropping them down and out.

Beers anytime

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An interesting contention to consider is the use of letters of consent by pilots and/or the airline when flying close quarters parallel approaches. It’s tucked away in some section of the .65 somewhere, I think…

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This sounds like @Maxmustang could’ve written this with simple English! Great topic and thanks for the helpful tips!

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@dylonez … MaxSez: I write utilizing aviation terminology where appropriate, aviator slang and lots of Segway’s. Brevity is key and Google is your friend. Parse it. LOL. Regards

Here’s a good overlay I made of the zipper method in action at KHOU. Extremely efficient method that we should incorporate into IF.

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