The DME Arc: How its done

How do you fly this weird thing with the new navigation features we have?

Figured this would be good to address as this question has come up a few times. If you’re someone looking to expand your skill with approaches and take them to the next level, you’ve found the right topic. This one is going to require some patience. Let’s proceed! 😃

This tutorial will be using the ILS Y RWY 4R at PHNL ~ Daniel K. Inouye International Airport (aka Honolulu International Airport)

Click on each of the drop downs below for the steps to get started:


Start here with the approach plate:

ILS 4R Approach Plate

Prior to starting an approach with a DME Arc, you’ll first need to figure out a few things:

  • What the VOR in use is
  • Where the Arc starts
  • And how far from the VOR the arc is

Once you have established these three things, you’ll proceed to tuning in the appropriate navigation frequencies needed to complete the intended approach.


Circled below you’ll find that I’ve circled in pink some information. Included in this circle is some helpful information:

  • 3000. This represents the altitude that this arc needs to be flown at
  • HNL: This is the VOR that you need to have tuned in
  • 13.9 Arc: This is the distance from the VOR that needs to be maintained to accurately fly this approach.


10 steps needed to fly a DME Arc

How to Steps

If you haven’t looked at the approach plate yet, go back and look at the above approach plate for 4R before continuing. Otherwise, the following steps will not make any sense. 🙂Happy Learning!

Step 1:- Tune in the ILS into NAV1 or NAV2 (If applicable) (Important note: not all runways will have an ILS)

  • Do not adjust CRS. Doing so will mess up your alignment with the runway and could off set you from the runway
    see “Runway CRS Alignment” for when you should adjust the ILS course

Step 2:- Tune in the VOR that you will be using for the approach. In this case we’re using the HNL VOR. Put this in the other NAV you’re not using for the ILS.

Step 2 ½:- For planning purpose, I would give you the option put in the approach waypoints in your flight plan. In my images and video near the end of this tutorial, you’ll find that I’ve added my waypoints on the approach into my flight plan. I did not use these to navigate but to reference where I was at on the approach. Just a helpful tip. 🙂

Step 3:- Determine where the DME Arc starts. If you refer to the ILS Y 4R approach plate, you’ll note that this approach starts at ALANA (IAF) IAF = Initial Approach Fix - A fix where all approaches will start

Step 4:- You’re just about to get to ALANA. It’s important to ensure that you’re at an appropriate speed for your aircraft. The aircraft needs to be stable. You do not want to be trying to slow the aircraft down, adjusting flaps, extending gear, etc while in the middle of the Arc. Get your flaps set, set your speed, set your altitude, and focus on flying the DME Arc. Once you turn onto final, only then can you proceed with lowering your gear, adjusting your speed, and lowering the remaining of your flaps (if applicable)

Step 5:- You’re all set. You’ve taken the previous steps into account and now you’re on your way to fly the Arc. As noted in step 2 ½ I’ve got a FPL set. I am not following it intentionally. As noted before, I’ve got the FPL there to reference where I’m at on the approach. Because Infinite Flight does not depict DME Arcs on our map, this will show as a straight line.

Step 6:- Refer to (DME Arc Image 1) for this step. There are a few things to note in this image.

  • NAV 1 is tuned into the ILS for 04R
  • NAV 2 is tuned into the HNL VOR
  • The upper most information block here is my source. This shows that my NAV 2 is active and being depicted on my heading indicator. This is what is depicting my large green needle (Course Deviation Indicator “CDI”)
  • The blue needles are called RMI (Radio Magnetic Indicator). You cannot adjust these with the controls you have. The only way to change these are to tune into a new VOR or change your heading.

Step 7:- Refer to (DME Arc Image 2) for this step. After you’ve noted the various components needed in Step 6, Step 7 has one tiny little feature to note, yet plays a crucial role in making this DME Arc turn out how it should. In this image, you’ll note that there is a little line/dot to the right of the heading indicator. For reference its aligned with the heading mark 005˚.

  • When flying your DME Arc, you need to use this line as a “90˚ mark” as a marker to keep a constant and consistent turn going in a way that I’ll explain next.

Step 8:- Using your RMI needle for your VOR, allow the needle to drop below this 90˚ mark by about 5-10 degrees. In the video below, you’ll notice that I was using 5 degrees to show that this arc is not a straight line.

  • Because the HNL VOR and the ILS for 04R were in line with each other, it may appear I’m using the ILS RMI on NAV 1 when turning. This was not the case. Important to note that some airports may have the VOR and your ILS location on different locations of the airport.

After you’ve allowed the needle to drop 5-10 degrees, its time to turn 5-10 degrees to the right in our example; the same amount you let the needle drop. Keep in mind the approach you’re doing may require a turn to the left.

You’ve been flying this DME Arc using your RMI needles. You will need to keep repeating this process until your CDI is within 10 degrees of the 90˚ line. (Refer to Step 6 & Step 7 for information about the CDI and the 90˚ line)

Step 9:- You’re within 10-15 degrees of your final approach course and your CDI is within 10-15 degrees of the 90˚ line. You will need to change your NAV Source so that you can now drive/fly off of the ILS now. A little bit of multitasking may be required here. At the same time, you need to start your turn to a 30 degree intercept to the final approach course.

  • In our example with 04R our final approach course is 042˚. For a 30˚ intercept we will need to fly from the arc to a heading of 012˚ to meet this 30 degree intercept. This will come quick so be prepared as you’re about to catch the localizer any moment!

Step 10:- You’re about to capture the localizer, you’re at 3000ft and looking good. Right on profile. As you continue your turn to align with the runway, you’ll need to hold this 3000ft altitude until your glideslope comes down to the point where you can follow it down to the runway.

  • For aircraft with retractable gear, this would also be the point where you would lower your gear, and add any remaining flaps that would be required to make a safe and successful landing.

To finish it off, lay down a greaser or execute a go around and go for an attempt #2


Runway Course Alignment

If on a visual day where you can see the runway, and you notice that you are not aligned with the runway properly, you may need to adjust the course of the ILS so that you are on centerline.

Why?

The charts that you may be using, and the charts that were used to build the airport you’re flying into may differ slightly when developed. 1 degree may be the difference between you landing on a taxiway and landing on your runway. In my video included in this tutorial, you’ll see that 042, the final approach course was not correct, but rather 043 was correct. Its small things like this that we as pilots need to be cautious of when approaching runways. Utilizing our map will help ensure that we’re not aligned on the wrong runway.

Reference Pictures

DME Arc Image 1

DME Arc Image 2

Video

Video intentionally has no audio. Didn’t want to bore you with the TBM sound for 9 minutes. Important time stamps are included below:

YouTube Video

ILS Y 4R HNL

Time Stamps:

00:20-01:05 ~ Permitted RMI needles to go in-front of the 90˚ line to bring my DME closer to that 13.9DME range as noted on the approach plate.

01:13-01:30 ~ 275 heading set. Permitted needle to drop 5 degrees. Turned 5 degrees to the right so that the RMI needle is pointed at the 90˚ line. Now at 280 degrees.

01:30 - 03:40 ~ Repeated same steps above. Drop 5, Turn 5, Drop 5, Turn 5 until I was within 10 degrees of the final approach course as my CDI points near the 90˚ line.

03:41 - 04:04 ~ Heading hold on AP goes off. I start my turn towards 012 degrees. Mid turn, I notice my CDI start to come in, so I continue the turn though 012 and onto 042, the final approach course heading.

05:42 ~ Glideslope captured. Time to descend below 3000ft

06:50 - 07:20 ~ I notice that I was not aligned properly. I was aligned too far to the right. I mistakenly tried adjusting CRS2 only to realize I was navigating off of NAV1. oopsie 😂I adjusted CRS1 to 043 to get me over to the left because I was on the right side of the runway. I turned towards my line, and as you will see, I got realigned with the runway on this new course.

09:00 ~ If you made it this far, you get to witness an ok ish landing


Questions?

Let’s hear them! If this worked, let the whole world know!

112 Likes

YAY! Tried to do an ARC the other day and it didn’t work out too well. Looking forward to trying out these steps and becoming a DME ARC expert.

Thanks, Deer! 😄

8 Likes

Hmm is this possible with live cockpit?

Yes, on the C172 & TBM903 the Primary Function Display (PFD) will depict these features as well. The RMI, CDI, 90˚ indicator line, it should all be possible. All other aircraft, you’ll have to do this in HUD.

2 Likes

It will also be possible in the XCUB with the glass cockpit as that’s the same screen.

And depending on if your VOR is in the flight plan you might be able to do it in the Airbus by keeping the VOR level with one of your wings on the NAV screen in NAV mode

1 Like

I literally had to do this yesterday on my approach into Tenerife with the ILS approach. Man, so usefull! Thank you!

1 Like

Who said you can’t have fun flying triacosihexecontagons 🤷‍♂️

Thanks for the tutorial 👍

1 Like

Quite a few airports today still use these types of approaches. You’ll find arcs that are long and relatively short in nature. Plus, they’re more fun (in my opinion) than straight in approaches.

2 Likes

Indeed. Was actually flying to Malaga today, and quite surprisingly it was using a DME arc for the approach… It was 26nm from the VOR and relatively short, though, so only a little turn.

1 Like

Thanks for the awesome tutorial. Time to give this arc another go!

Great tutorial! I presume as of now this can only be in HUD mode on commercial jets w instruments?

Ah!!! I have been waiting for this for years! Let’s go.

How to tune ILS to Nav 1 or Nav 2

Thanks for another great little tutorial. I’m enjoying all the new navigational functions we can do now on IF I’ll be trying this one out for sure.

Great tutorial! I really like this type of procedure. I hope that in some update DME will be added to make an arc exactly the same in real life, however, the way VOR is currently, it is already good :)

I love this procedure, great tutorial!
I use it a lot in Mexico

3 Likes

Screenshot 2019-12-30 at 20.11.01
Finally did my first DME Arc approach today after hours of fussing over trying to interpret the steps in this tutorial. Not only is the approach easier than expected to fly, but it was all hand-flown, making it quite fun.

7 Likes

Here’s my first attempt. For some reason the two blue arrows never lined up, so I was just turning visually

Well for flying the arc alone, you only reference the RMI for NAV2.

DME Arc of today! ❤️

5 Likes