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martinlest2

ATC and final turns. How does it work in RW flying?

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I am doing a bit of low-key  beta testing for PF3 (ATC software) and to clear up one issue, I wonder if any real-world ILS rated pilots who 'can't get enough' of their job and read the AVSIM forums could say exactly what the procedure is for turns onto final approach, at airports with ILS.

 

Presumably, as a/c get near to the localiser, the autopilot is already armed to intercept the runway heading. Does the pilot have to wait until ATC instructs him/her to make the turn, or is it taken for granted, as it were, that when the localiser is intercepted and the needle starts moving to the centre, the aircraft will turn to the runway heading without further permission from ATC?

 

I am not of course talking about permission to land here, but the earlier permission to change course to the runway heading, weather manually or with the A/P. How exactly does that work -  at what stage does ATC tell the pilots they are OK to the turn to runway heading?

 

Could I kindly ask, BTW, that only people who know about this from real-world ILS flying experience answer this question, rather than people (like me) who think they know, but just from books, or from the internet, or from FSX/FS9 and so on, as too many of these threads thereby seem to end in misinformation, then arguments and finally insults! :smile:

 

Thanks a lot.

 

Martin

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I would like to answer but can't because I don't have real life ILS experience myself. :)

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Once atc clears you for the approach or instructs you to intercept, you are free to join onto the course.

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I would like to answer but can't because I don't have real life ILS experience myself. :)

:smile:   I was just trying to prevent this thread going the way of some others I was looking at recently, but please do comment LOL

 

Once atc clears you for the approach or instructs you to intercept, you are free to join onto the course.

Quite, but I was asking when is that clearance given.

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You asked whether the pilot has to wait for atc to turn them onto final or they can turn when the needle moves without further instruction. The approach clearance or instruction to intercept constitutes the permission to join onto the course when the needle moves. You would not arm any approach or nav mode on the autopilot until you have heard such a clearance or instruction from atc. So arming the autopilot to intercept is definitely not presumed. If your actual question is when atc will issue the approach clearance, then that is a question for a controller, not a pilot. Google something along the lines of air traffic control handbook for the details of when they are allowed to cut a plane loose for the approach.

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ATC would give you an intercept heading to "intercept" the localiser, you don't intercept the localiser on your own. With that final turn, usually comes the ILS approach clearance. A good intercept is 30 degrees, so if the runway track is 360, then ATC would give you a heading of 330 or 030 (depending on where you are, of course).

When given clearance to intercept the localiser, you then arm the autopilot LOC mode....

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On top of what's been said before, on some airports (such as Madrid, LEMD) it's instructed in the charts that the pilot can intercept the LOC when on an intercept heading and when the frequency is so busy that the aircraft doesn't have enough time to ask.

 

This is done to prevent the aircraft from flying straight ahead into the approach area of a parallel runway.

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I fly in to a large airport with 3 parallel landing runways.  They will bring you in on a 90 degree intercept to the localizer to about 2-5 miles from it.  Then they will tell you to fly a 30 degree intercept to the localizer. 

 

You cannot let most planes intercept at 90 degrees.  Most of them will overshoot and end up in another approach corridor.

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Flying the course instructed by FSX/P3D ATC almost always bring you in at 90, turning onto 60, then finally 30. One reason is the standard autopilot can suffer from latency and oscillate a little too much with a 45/45 approach and certain planes.

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finav77 was correct.

 

Just to share my little real life experience flying around the world. In real life, the approach controller will, at the latest, give pilots an intercept heading to intercept the final when the airplane is about 2.0nm from the extended runway centreline. This is very common in Narita, Hong Kong, LAX, ORD or JFK, when ATC tries get you on the ground as soon as possible. 

 

And the shortest final distance for an ILS approach should , in general, between 6-7nm from the rwy threshold (not from any book, this is what I normally get unless clear for visual approach).

 

Very occasionally, the approach controller would say to the pilot they intend to vector them through the localised for extra spacing, in this case, one shall expect to fly across the extended runway centreline.

 

However, for good airmanship, every time when we, on base leg, fly pass 2nm from the runway centreline and not getting anything from atc saying "expect vector across the LOC", we shall ask ATC for his/her intention. Especially when flying to airport with parallel runways conducting independent approaches. It happens quite often that sometimes the controller just simply forgets about you. 

 

normally for the 777, speed is about 180kts on base leg with flap 5 or 15, assume no tailwind, the airplane will fly pass the LOC is we don't start our turn in less the 2nm from the runway centreline. Even the AutoPilot cannot defy the law of physics which defines the radius of turn of the airplane as a function of Groundspeed. 

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However, for good airmanship, every time when we, on base leg, fly pass 2nm from the runway centreline and not getting anything from atc saying "expect vector across the LOC", we shall ask ATC for his/her intention. Especially when flying to airport with parallel runways conducting independent approaches. It happens quite often that sometimes the controller just simply forgets about you. 

 

In some airports such as Madrid Barajas, LEMD, the charts instruct the pilots to intercept the LOC even if the ATC doesn't explicitly tell them to do it. Precisely because of the parallel approach sectors.

 

Can you think of more examples in which that would be the case? :)

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hmmm... I believe it is the case when the chart doesn't say anything about you are allowed to intercept the LOC on a radar vector without atc permission unless cleared for procedural ILS from the IAF approach, because there are time when they really need you to go across. Again I am speaking from the experience I have in the area where I spend most of my time flying in, no reference to the books. Every time when I am not happy, I will just ask atc to clarify their intention. 

 

But, hey, thanks for the heads up!!! I will have the opportunity to fly the Madrid starting from this summer, any local knowledge would be highly appreciated!!  :smile:

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But, hey, thanks for the heads up!!! I will have the opportunity to fly the Madrid starting from this summer, any local knowledge would be highly appreciated!!

 

You're welcome!

 

Here, have a look at this (click for larger image):

QhseSmt.jpg

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I see what you mean Jaime, I like that the fact they put the notice like that in Madrid. It really does help to reduce the likelihood of inadvertent LOC overshoot.

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