When to start the final turn to get lined up for ILS?

#1

Hi all,

I searched and couldn’t really find the right answer.
If I missed it, I’d appreciate a link to it.

My question is how to know when to make the final turn, using the AP HDG, to get lined up for ILS after being on left or right base.

AP has a fixed amount of degrees it turns the aircraft.
I always sort of intuitively turn, but is there a better way to get right on the ILS line?
I don’t like having the make the S-turns to get lined up.
Using the map isn’t the best way, cause it depends on how far you’re zoomed in or out, which you can’t see, as far as I know.

All suggestions and advice is appreciated.

Thanks!

Jan

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#2

I don’t know, I usually use my hands to control when on left base, I recommend you to use your hands too.

And the distance from the extended center line where you start the turn also depends on the speed from my previous expts. I expect an answer with speed guidelines

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#3

Thanks!
I’m usually between 160 and 180kts when I’m entering the red guides on the map. I don’t know what they’re called.

#4

Just practice a bit. Eventually
a) you will get a feel for when to turn
b) you will feel confident enough to start using your hands for the turn :)

#5

I second that. Intercept at 30 degrees or less and you practically can’t miss the LOC. Speed 180-200kts until 6NM, then final app speed. That’s how I do it.

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#6

Manually turning isn’t really the issue. I succeed at that, because of tiny adjustments and different turn angles.
Doing it right using AP is my issue. :)

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#7

If you don’t want to over correct, try lowering the sensitivity. Makes it easier to stay steady on the localizer and you really don’t have those moments where you over correct and go around.

#8

It’s not that.
It’s about knowing when to start the final 90 degrees turn coming from left or right base using HDG in AP mode. Is there a specific procedure?

I read about way-points and their distances to turn based on speed, but when in a pattern there are no way-points, so you don’t know the distance to the turning point. How much time the turn will take doesn’t help in that situation.

#9

I suggest turning from base diagonally to the start of the ILS cone, this will make it easier to then turn onto 30-/20-/10-degree turn to intercept, this is how many advanced controllers do it, also controllers IRL.

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#10

Good point!! Thanks!

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#11

Also, flying in to intercept the ILS at 2500ft AGL. Then if you are not lined up straight away it doesn’t matter.

#12

I usually start at 3500 or 3000ft.
APPR takes you to 3500ft anyway, so…

#13

Depends on airport procedures.

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#14

Hi I will tell you how I do it. (Not sure if that the correct way but it’s working for me. You should always intercept the localizer at about 30 -45 degrees. The speed you should intercept it should be about 180 knots. In your hood where the ILS Is you can see 2 dots on the left and 2 on the right. The outer one is called outer marker the inner one is called inner marker. In real life pilots get a beep when they reach the markers. My personal experience shows that at 180 knots 30 degrees in the localozer I start my turn when my line is on the inner marker. It will not line you up exactly. But with little adjustment you will be ok. Hope that helps. Also there is a video on YouTube. Don’t know exactly the title but it’s very well explained.

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#15

Another good way to find out is get an aircraft with APPR. A320 or Boeing 737 BBJ. Intercept the localizer at 30 degrees and hit the APPR button. Pay attention when the aircraft will start the turn

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#16

Of course. Normally tower gives you a speed restriction until a certain distance. Mostly 160kts until 5NM from what i heard on LiveATC

#17

Hi Jan,

I understand what you’re trying to do here. The thing you want to find out is called the “radius of turn”, so if you look that up you can find some pretty good information.

Here something that will work to line you up VERY close to the centreline of the ILS using autopilot. I just did a quick test.

Test: landing ILS 19L at KSFO
Aircraft: A321
TAS: 160kts
Weather: no winds

  1. First thing you need to do select a waypoint that is positioned directly at the beginning of the Runway you want to land on. Then click on the “Direct to” button in the flight plan page. Now make sure the control bar at the bottom of the screen is able to show “distance to next” and “bearing to next”.

  2. When you’re on the base leg take a note of what the exact runway direction is. For example 19L at KSFO is actually 193 degrees. So if i’m on Left base i’m going to fly 283 degrees.

  3. You want to be positioned about 8.5 nautical miles from the waypoint you selected when you start to turn. This is difficult to guess so instead start flying directly to where the beginning of the red ILS lines begin and it should be ok.

So now you’re ready to turn! At this stage you should have 160kts set on the autopilot and be flying a heading that is perpendicular to the runway making sure that you are flying to the end of the red ILS lines.

  1. Now you just need to look at your “bearing”. when your bearing is about 9 degrees from your exact runway heading, tune the autopilot to the exact runway heading. and thats it. In the test i did, i waited for the “bearing” to say 202 degrees (202-193=9), then is started to turn and ended up on the ILS perfectly.

Sorry this is very long, I just wanted to explain properly. Obviously if you’re going faster than 160kts or you’re further than 8.5nm away this wont work. If you want to get technical, look up the rate of turn formulae on wikipedia. For your information the “bank angle” is 20 degrees in IF.

Thanks,
Rooster

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#18

Thanks!
I will definitely try this.
👍

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#19

We use for a 90 degrees turn, 0.5 X GS / 100. and this is based up on a standard 3 degrees per second turn. To determine the distance is a bit difficult with IF…

For example GS 200 = 1 NM

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#20

Thanks Aernout.

Interesting!
Shame the turn rate can’t be set.

When flying manually it’s also hard to determine since the first increment on the bank indicator is already 9%.