CAT 1 ILS APPROACH

[glideslopealive]

Upon reaching the minimums of 200ft AGL in an ILS cat I approach, and the runway is clearly in sight, can the Pilot continue to follow the glideslope all the way down to touchdown when he is not cat II or III certified?

[Piltdown Man]

Of course, that is exactly what they are meant to do. Furthermore, if the weather is less than Cat I and the runway or approach lights including a lateral component can be seen you can still continue. The important thing is not to pass the outer marker (etc.) when the reported RVR is less than the required for the approach. Just out of interest, why did you think otherwise?

[aterpster]

If it is a CAT I only ILS, the G/S may or may not be reliable below DA. Depends on the particular installation.

[Piltdown Man]

No matter what sort if ILS is being flown, the glideslope should be followed until the flare and roundout. That can be done on one of two ways, the glideslope indicator of the PAPIS.

EDIT - What I meant to write was: "That can be done in one of two ways, the glideslope indicator OR the PAPIS".

What is more correct is: "The nominal glideslope should be followed until the flare and roundout. The information to do this is provided by many sources, including but not limited to: Glideslope indicator, PAPIS or equivalent, V/S and power setting, Visual perspective of runway and/or runway edge lights, peripheral vision and associated textural clues. Care should be taken at some airfields where the integrity of the glideslope signal is not garanteed below certain heights and/or there is a mismatch between visual slope guidance systems and the transmitted glideslope."

[galaxy flyer]

The important thing is not to pass the outer marker (etc.) when the reported RVR is less than the required for the approach.

Maybe so in commercial ops, but not in FAA Part 91. Not to say it is always smart.

[RAT 5]

GS Alive: will you please explain why you are asking the question. The answer is so basic that I wonder where is the confusion.

[RAT 5]

the glideslope should be followed until the flare and roundout. That can be done via the PAPIS.

You sure about that?

[mustafagander]

Piltdown,
That is utter rubbish, dangerous rubbish. Below charted minima the G/S is very often out of tolerance, often wildly so. Visual is meant to be just that, visual. I'm not saying don't keep an eye on it but do not be surprised if the G/S is no good below mins.

[simmple]

In marginal visual follow gslope or there is a tendency to dive for the lights.
Good visual ignore it and do what it says on tin, fly visual!
It really annoys me when good visual and fo flying he will look at glide slope when all looks good out of the window and dive or climb to get back on slope for the smallest of deflection and basically cock up what was going to be a good landing!

[aterpster]

Surely, there are some armchair pilots in this thread.

[Amadis of Gaul]

Only in this thread?

[Piltdown Man]

I hope this is classic case where people have started shouting because of a spelling mistake. "of" should have been "or". But I'm sure I still have to be shouted at because at times I think I do a different job to everyone else. I base my unworthy opinion on being unfortunate enough to have landed 10,000 times or so at airfields where the glideslope will probably take you right into the touchdown zone. Rather surprisingly I have also been trained fly visual, non-precision, CAT 1 alll the way to CAT III. I have wrongly undersood that during every instrument approach there comes a time when you have to transition from the clocks to a flare and roundout. Recklessly and obviously very dangerously whenever I have had the minimum required visual references I have continued to follow whatever references I have had available to me to follow the nominal glide to the touchdown zone. I have used a combinations of glideslope, PAPIS (if present and visible), relative movement of runway image etc. Obviously wrong. So would someone tell me what a safe professional pilot should use? Obviously I also don't understand the validity of G/S signals. I thought they were valid until at least the minimum height for the approach plus a healthy margin to allow a visual transition, if you call 50' on a CAT II approach healthy. I'm all ears and eager not to kill either my passengers or myself.

[aterpster]

I stated previously that the G/S is reliable all the way to touchdown in a CAT II ILS. It may or may not be reliable below DA on a CAT I ILS. There is no required margin below DA, at least in the U.S.

If you have been qualified on fail-active CAT III autoland you should have been trained that it is mostly RA that is controlling the vertical path below 100 feet.

As to CAT I, at least in the U.S. you are supposed to rely on visual cues below DA. Those fortunate enough to have a modern HUD, have a calculated vertical path that is displayed with the runway symbology below DA.

If the runway has a VGSI and you can see it, so much the better.

In the 1960s and 1970s the FAA falsely asserted that approach lights provide vertical guidance. After a couple of low visibility accidents they backed away from that assertion.

My own experience was that I always saw the first part of the runway at DA on a CAT I ILS. The runway perspective, even a small portion does provide a vertical sight reference.

[Amadis of Gaul]

No matter what sort if ILS is being flown, the glideslope should be followed until the flare and roundout. That can be done on one of two ways, the glideslope indicator of the PAPIS.

Strictly speaking, if you're following PAPI, you're not following the glideSLOPE but rather the visual glidePATH which are usually not coincidental. They're close enough for guvmint work, but not exactly the same thing.

[Piltdown Man]

AoG - You are correct.

[aterpster]

Strictly speaking, if you're following PAPI, you're not following the glideSLOPE but rather the visual glidePATH which are usually not coincidental. They're close enough for guvmint work, but not exactly the same thing.
Can only speak about the U.S. At most air carrier airports the objective is to have the VGSI angle coincident with the ILS G/S.

The not-coincidental note is more common on RNAV APVs where the installation of the VGSI predated the design of the RNAV approach and the VGSI is set higher for noise abatement. Policy in that case is to not compromise the RNAV APV slope to match the VGSI slope.

[Amadis of Gaul]

Can only speak about the U.S. At most air carrier airports the objective is to have the VGSI angle coincident with the ILS G/S.



Is that so? In my 10+ years of flying into "Air carrier airports" in the US, I can only think of a few ILS approaches where that note was NOT present.

[aterpster]

Cite some examples please.

[Amadis of Gaul]

Cite some examples please.

My absolute pleasure. The note IS present on all ILS approaches into JFK that also have PAPI except for 22R

We observe the same at ORD.

We observe the same at ATL

And at LAX

And at DTW

And at BOS

And at FLL

And at DFW

And at IAH.

Need more examples or is that enough?

In fact, 22R at JFK is the only runway I found that has both a PAPI and an ILS where that note is NOT present.

[aterpster]

You're right. But, they must be splitting hairs. Take LAX 24R for example, both the VGSI and the ILS GS are 3.0 degrees. No TCH is shown for the PAPI, so that can be the only reason for the note. I suppose most pilots would scratch their heads if they even read the note.

[aterpster]

This is from an FAA friend who is the consummate expert on this stuff. I presume this applies wherever the G/S and VGSI angle are identical:

The TCH must be within 3 feet to be coincident. Unfortunately, the way they set up the VGSI is to generate a TCH for the pilot’s eyes, which is 15 – 20 feet higher than where the ILS is.

[Judd]

In several airports in Australia serving international (wide body) aircraft there is a chart note depicting PAPI MEHT or Mean Eye Height at Threshold. Typically 72 feet. This is because the PAPI installation is further down the runway than a normal PAPI to cater for a long aircraft (wide body) Thus on an ILS 3 degree indication on slope for a Boeing 737 for example, a PAPI will show 3 reds and one while.