'intercept LOC' can be substituted to 'intercept G/S as well'?

[FlywithPark]

I've seen some pilots regard "intercept localizer" to "intercept G/S as well" so when they capture G/S they begin to descend though the path.(for ILS approach)
For me, i understood that i only have to intetcept LOC because ATC allowed only LOC capture(even though we're above G/S)
But other people say we don't need to wait.
How's your opinion?

[AerocatS2A]

In this part of the world you are not cleared to descend on an instrument approach (precision or non-precision) until "cleared for the approach", so being cleared for the localiser does not include clearance for the glide slope.

[Check Airman]

"intercept the localizer" means just that in FAA-land

[de facto]

Worrying indeed...

[Skyjob]

LOC intercept is just that. Do not descent on G/S until cleared.

Terrain restrictions below may require an initial higher than G/S stepped down descent and capture the G/S from above (e.g. ALC runway 10, when completing the procedural turn flying a large DME arc, mandatory speed 180kts, vertical profile is high until ~10nm final, G/S signal may scallop due terrain until then providing "false" G/S signals).

Airspace restrictions below may require an initial higher than G/S descent to clear airspace below the G/S reserved for other aircraft or airports (e.g. BHX runway 33 when arriving from South-East [London] requires overflying CVT, especially busy in VFR weekends).

ATC may have VFR/IFR traffic below you, again causing, sometimes this traffic is not carrying a transponder with altitude information thus you (operating crew) cannot see them necessarily. However ATC may be aware and thus not (yet) allowing you to descent on G/S until clear of traffic.

All respondents are so far correct: do not, unless "Cleared for Approach".

[flarepilot]

one exception...you can be cleared to intercept and track the localizer and descend on the glideslope , maintain 3000'(for example ) and be told to expect approach clearance upon reaching 10 dme, or leaving 4000'.

but I agree...intercept and track inbound on the localizer is not a clearance to descend (unless additional verbiage included in clearance) or an approach clearance.


now if you are told to intercept and track localizer, descend and maintain 2000'...you could follow the glideslope, but you can't go below the cleared altitude. however, all altitude changes are usually assumed to be made at best rate

[HEATHROW DIRECTOR]

If you have been told just to establish on the localiser do not do not descend further until ATC clears you. They may be providing separation against other traffic beneath you. If you are just cleared for the ILS that is a different matter.

[Check Airman]

This is worrying. It's the sort of thing that I taught my students on their second or third IFR lesson.

[bubbers44]

Me too. Cleared for the approach lets you descend on GS. My retirement final landing they failed to do so and with congestion was unable get landing clearance to descend until glide slope was pegged full down. Salvaging the approach made a less than ideal approach and landing but that was before the stabilized approach rules. Going around with an intersecting runway with departures at the far end wasn't The way I wanted to retire.

[flite idol]

Cleared for the approach lets you descend on GS

Not necessarily. You are still bound by any stepdown fixes until the final approach segment. I have had this discussion on the flightdeck inbound to LAX with very experienced pilots who think they can join the GS when cleared by atc to "fly XXX arrival, cleared for ILS 25L" and have seen folks arm the approach and grab the GS at 10,000'+. The link below is a good reference.

http://www.faa.gov/other_visit/aviat.../InFO11009.pdf

[bubbers44]

LAX 25 approaches will put you below step down alt if on GS.

[aterpster]

Check Airman:

This is worrying. It's the sort of thing that I taught my students on their second or third IFR lesson

But you weren't teaching FS pilots.

[BOAC]

The problem as I see it is that 'FlywithPark' might not be an FS pilot?

[latetonite]

He must be. Any professional pilot nowadays has an instrument rating included in the 190 hr package. On top of that there is a level 4 ELP required, I believe.

[cosmick251]

... the way I've been taught, do not leave your assigned altitude until you receive an approach clearance. An instruction to intercept the localizer, is simple lateral guidance and does not constitute an approach clearance.

[Capn Bloggs]

Not necessarily. You are still bound by any stepdown fixes until the final approach segment....

The link below is a good reference.

http://www.faa.gov/other_visit/aviat.../InFO11009.pdf

"On ILS approaches, stepdown fixes are established for obstacle or traffic separation.".

"On both days your flight path on the glide slope was the same, but on the hotter day, the stepdown altitude, crept up into your glide path."

How is a hotter or colder day going to change the vertical separation with terrain when tracking the glidelsope?

Fair enough steps limited by airspace (1900ft at the bridge!) are affected by temperature and pressure when on the GS but obstacles?

[aterpster]

Capn Bloggs:

"On ILS approaches, stepdown fixes are established for obstacle or traffic separation.".

"On both days your flight path on the glide slope was the same, but on the hotter day, the stepdown altitude, crept up into your glide path."

How is a hotter or colder day going to change the vertical separation with terrain when tracking the glidelsope?

Fair enough steps limited by airspace (1900ft at the bridge!) are affected by temperature and pressure when on the GS but obstacles?

The GS isn't affected by temperature but step-down fixes are. The GS cannot be used as primary for vertical navigation until the P-FAF. The step-downs are primary for vertical guidance prior to the P-FAF. Step-down fixes rise when its hot and descend when its cold. The hot day is when separation from other aircraft can be lost.

On a really cold day obstacle clearance can be lost.

[Capn Bloggs]

Thanks Aterpster. So apart from really cold days (I assume any GS limitations in this case would be on the chart), the FAA statement that stepdown fixes established for obstacle separation may be limiting or hot or cold days even when on the GS is tenuous at best?

[Capn Bloggs]

Yes, OK, I was just querying the FAA's implication that obstacle clearance could be compromised if you followed the GS on a hot or cold day.

I understand that airspace steps can be an issue if you are on the GS when hot or cold. GAATE and HUNDA are obviously not terrain limits.

[aterpster]

Capn Bloggs:

I understand that airspace steps can be an issue if you are on the GS when hot or cold. GAATE and HUNDA are obviously not terrain limits.

The GS is not controlling until LIMMA. Further, the GS remains at the same true altitude both outside and inside LIMMA.

So, outside LIMMA on a hot day the step-down fixes rise above the GS. The step-down fixes separate traffic below, not the GS. This has been an issue at LAX, SEA, and ORD.