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\"Intercept LLZ\" question

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EHM-1617 Iain:
Hi

I can only comment on the situation on IVAO in the UK, which mirrors what happens in real life in the UK.

First of all, we do not use the phrase "Cleared ILS runway XX". The reason for this is simple: using that phrase gives away control of the altitude to the pilot. Many pilots, on hearing this, descend immediately to the published Glideslope Intercept altitude and this could create problems with traffic below or even terrain.

Instead, we use "report established on the localiser" or "report localiser established". These phrases mean that you should maintain heading until you can make a smooth turn on the localiser. Realistic add-on autopilots simulate this very well - even at extreme intercept angles. (Incidentally Ricardo, here we are allowed intercept angles between 30 and 45 degrees, with 30 or 40 degrees being the norm).

Then, when the pilot reports established on the localiser, we say "descend on the ILS". This means that altitude should be maintained until intercepting the glide and then a smooth descent should be initiated. During periods of heavy traffic, the two phrases can be combined into "when established on the localiser, descend on the ILS", to which the response is exactly the same.

Let me try an example; EHM123 is inbound into Heathrow's 27L from the north side. '...' denotes a pause.

"EHM123 turn left heading 120 degrees, 26 miles" (26 miles refers to the distance from touchdown, for descent planning)
"EHM123 descend to altitude 4000 feet QNH 997 millibars" (self-explanatory)
"EHM123 contact Director 120.4 callsign only" (transfer to the final director; the check-in should be just "EHM123")
...
"EHM123 good evening 19 miles" (the distance from touchdown again)
...
"EHM123 turn right heading 180 degrees, speed 180 knots" (base leg)
"EHM123 descend to altitude 3000 feet, 14 miles" (final descent and check of distance to go)
...
"EHM123 turn right heading 240 degrees report localiser established runway 27L" (the pilot begins a right turn to heading 240 and maintains it until he intercepts the localiser)
...
(reports established)
"EHM123 descend on the ILS speed 160 knots until 4 DME" (maintains 3000 until intercepting glide)
"EHM123 contact Heathrow Tower 118.5"

That's how things work on IVAO and in real life in the UK. Hope I have helped some.

EHM-0641 Rico:
Iain, not even Gaz could have explained it better :P

EHM-2097 Andrei:
Hi all,

First of all, thanks for your answers. Then, taking into account these answers, I think it's time to draw some conclusions.

First, I think most of us agree on the right way to intercept the localizer - as a pilot: start manually the turn into the localizer and intercept glideslope from below.

About the ATC instructions, I also red the iCAO 4444 document and it gives a few hints (= rules, in fact :) ) :


--- Quote ---The pilot should be instructed to follow a heading within 30 degrees before LLZ interception AND must be granted at least 1nm of straight flight before intercption. There is no indication of upper limit here.
--- End quote ---


(Of course, local procedures may override this as I suppose it is the case in the UK according to Iain's detailed example.)

In this case I keep my opinion that "intercept" should be read as "clear to intercept as you approach the LLZ axis" and not as "turn now to intercept".

However, it may well be a reality on IVAO that some pilots may misinterpret (well, I saw one :) ) the instruction so ATC should be prepared for it. As "tactical" preparation I see two measures:

- The angle between last assigned heading and LLZ - the lower it is, the less zigzag turns occur if APP is triggered too early;

- The timing - the later the "intercept" instruction is isued, the lesser the effect of any misinterpretation is. Personally I will impose myself a 5nm limit (before intercepting).

HOWEVER... the main issue here remains the phraseology, as this is what causes or dissipates misinterpretations.

I agree with Sotiris that little nuances can do much (good and bad). In this directon I think that "cleared to intercept" is better than "intercept", because it does not suggests immediate action to be taken (like pressing the unfortunate APP button).

However, "report established" alone is not sufficient in my opinion because this does not clear the pilot to turn when reaching LLZ axis.

By the way, "report established localizer" is also subject to different interpretations. I've heard pilots reporting as soon as they pressed "APP" while others did not report until the heading was completely stabilized. And of course I don't dare skip the "localizer" from the "report established" sentence because in this case some pilots may only report when established on glideslope too.

(I must add to this that official documents like the 4444 above mentioned are not very specific about this topic - the exact meaning of "established").

See you online
Andrei

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