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moey124

ils approach do I press loc or app on mcp

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Wel I clicked loc and the plane turned to the runway and when should I click app or loc is the same &@($* app on mcp. Cause my plane wasnt descending.

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LOC is just the localizer. APP would be the actual approach, which you would press once the glideslope comes alive.

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Wel I clicked loc and the plane turned to the runway and when should I click app or loc is the same &@($* app on mcp. Cause my plane wasnt descending.

 

I'm only a novice but on an ILS approach I think you just need to press APP to pickup the glideslope. I am not pressing the LOC button at all. APP seems to capture both the localiser and glideslope.

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Usually you would capture the localizer first, and then the gs. So 1st hit LOC and then APP after

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I'm only a novice but on an ILS approach I think you just need to press APP to pickup the glideslope. I am not pressing the LOC button at all. APP seems to capture both the localiser and glideslope.

Not all approaches are full ILS approach. There are some that are localizer only approaches, which is where the LOC button also comes in handy.

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But how do u know when u entrred the glidescope cause I hit loc and it truned to rjnway after passing one more star on the display I hit app but it didnt desend

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LOC will follow the Localizer. 

 

This is a system which transmits a radio beam of sorts that shows where the aircraft needs to track, and will cause the autopilot or flight director to command a correction - left or right - if it detects any deviation of the course from the radio beam's centreline (which at some places like Innsbruck or Kai Tak would be a radio transmitter on a hill somewhere, but at most airports would be a radio transmitter at the far end of the runway you are landing on).

 

APP mode follows both the localizer and the glideslope.

 

I repeat, LOC does NOT follow the glideslope.

 

The glideslope is like the Localizer, but it defines a descent path. If your autopilot is in APP mode, it will follow the descent path, and make corrections - up or down - if it detects any deviation of the glidepath defined by the radio beam's centreline (which at some places like London City EGLC is a 6.6° decent angle, but at most airports is closer to 3°.)

 

 

If you arrive at an airport ILS and press the LOC button, it will fly a track which flies directly over the runway centreline. It will maintain whatever altitude you have set on the Altitude Hold on the MCP.

 

so you will fly over the runway, dead on centre with the white lines in the middle of the runway, at 3000ft above the runway.

 

On the 777 here, there's an airline option to inhibit glideslope intercept in APP mode if you are not established on the Localizer. This means that when you hit the APP mode, the aircraft will need to be in LOC mode (Green, not Armed/White look at the PFD) before the Glideslope can capture. If you arrive "Above glideslope" then it will not 'descend to meet the glideslope'. This means the aircraft will not descend with the glideslope when it is not near the localizer. This is deliberate to protect the aircraft from descending with the glideslope when it isn't on course. an ILS has a surveyed protected area where by the glideslope is guarenteed to not hit hills and buildings etc. If you are 3 miles left of that, the glideslope might hit a hill, causing lots of dead 777 passengers. To avoid this, intercept the localizer on vertical profile if on an RNAV arrival, or as a general rule when using self-vectoring, more than 12 miles out and no more than 3000ft above the airport elevation.

 

In the PMDG 777, there's an option to turn this feature off, and so you can intercept and descend with the glideslope in APP mode even if you are well left or right of the localizer. This way the Autoland will still arm, and... assuming you don't crash into hills and structures on the way down, touch down on the glideslope somewhere near the runway, possibly even on it.

 

Here's some more things to consider when using an ILS. (To avoid confusion, this "False/Erroneous glideslope" problem won't happen in Flightsim FSX)

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LOC should always be selected first. After established on the LOC (LOC green on FD), if you require a full ILS/Autoland, then press APP. GS will display in white on the FD until glide slope capture, at which point GS will turn green.

 

Regards,

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LOC should always be selected first. After established on the LOC (LOC green on FD), if you require a full ILS/Autoland, then press APP. GS will display in white on the FD until glide slope capture, at which point GS will turn green.

 

Regards,

 

"Always" is a pretty strong term.

 

Try the LIZZI7A Arrival 16 at YMML, It's an RNAV with a 180kt max speed 90 degree left turn at 4000ft 13 DME from Melbourne.

 

The localizer and glideslope both intersect the RNAV section IN the turn at Bolinda BOL (ndb 362)

 

If you have APP mode selected as you start the turn, you will roll out wings level descending and with LOC & GS mode active.

 

If you don't... you'll probably be at 4000ft 2 dots above slope and increasing.

http://www.airservicesaustralia.com/aip/current/dap/MMLSR05-135.pdf

 

Without rolling the MCP altitude window down and getting onto FLCH quick smart, then getting back on glideslope will be a bit of a battle. Intercepting the Glideslope from above out of FLCH is an option, but it's not the best option.

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"Always" is a pretty strong term.

 

Try the LIZZI7A Arrival 16 at YMML, It's an RNAV with a 180kt max speed 90 degree left turn at 4000ft 13 DME from Melbourne.

 

The localizer and glideslope both intersect the RNAV section IN the turn at Bolinda BOL (ndb 362)

 

If you have APP mode selected as you start the turn, you will roll out wings level descending and with LOC & GS mode active.

 

If you don't... you'll probably be at 4000ft 2 dots above slope and increasing.

http://www.airservicesaustralia.com/aip/current/dap/MMLSR05-135.pdf

 

Without rolling the MCP altitude window down and getting onto FLCH quick smart, then getting back on glideslope will be a bit of a battle. Intercepting the Glideslope from above out of FLCH is an option, but it's not the best option.

I stand corrected. I should have said "almost without exception" however for the benefit of the OP, read the last paragraph on page 91 of Tutorial #1.

 

Regards,

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Another instance that will happen is that ATC will give a clearance to intercept the localizer but not clearance for the approach.

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Another instance that will happen is that ATC will give a clearance to intercept the localizer but not clearance for the approach.

Would this be if ATC was considering issuing a side step in the case of parallel runway?

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I guess it could be. I have gotten it for guidance to the airport and if there are multiple planes in line for the approach.

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Would this be if ATC was considering issuing a side step in the case of parallel runway?

 

On VATSIM it's usually when ATC is considering forgetting about you then wanting you to land from a position 2 miles short of the runway at 3000ft.

 

I once decended on my own with the slope and was told that I wasn't cleared for that, so I climbed back to 3000ft. When they issued the clearance for the approach I declared a missed approach due to being too high instead of reading the clearance for approach back. When they asked for clarification about the go around I told them that the reason that I was too high was due to him telling me to climb back above glideslope and maintain 3000ft. He somehow didn't realise that 11 miles from a runway at 3000ft is on the 3°.

 

He then cleared me to climb to the missed approach altitude.

So I descended to the missed approach altitude of 2500ft and read back "Descending to 2500ft missed".

 

yea, I get a bit snippy sometimes, but you can't climb to an altitude below you, and sometimes stuff needs to be said.

 

 

In my opinion, the main reason you don't hit APP mode straight away is the possibility of false glideslope capture. False glideslope is a feature of how glideslopes function (has to do with some physics of electromagnetic radio broadcasting) and if you arm APP early, it may capture a ~1° glidepath which is well below where you should be. Making sure you don't arm APP before the proper approach fix prevents this procedurally.

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