Arrival and ILS question

[Checks]

oopps

 

[TonyC]

Take a look at the approach plate for the approach in question.

http://204.108.4.16/d-tpp/0505/00320I26.PDF

It specifies a MANDATORY 2000' at GS intercept. If it didn't have the mandatory, you could just join it at your present altitude and fly it down.

Thaks for posting the link.

I'm more accustomed to using Jepps theses days, so I might be off here, but...



In the profile view, I see 2000 in large font three times. On the far left, and appearing to apply to the crossing at ESKOE, the final approach fix. It has a line drawn above and below it. If I recall correctly, that means it is a mandatory altitude. I would interpret that to mean I must cross ESKOE AT 2000 feet. In smaller font directly above the Maltese cross at Eskoe is the Glideslope crossing altitude at ESKOE - - again, 2000. That indicates to me that the glideslope crosses ESKOE at exactly 2,000 feet.

How'm I doin' so far?


The second large font 2000 to which I draw your attention is the one just to the right of FOSOM, an intermediate fix on the approach. The 2000 to the right of that fix has a single line drawn underneath it. I believe that means the crossing altitude is a MINIMUM altitude. One must cross FOSOM at or above 2,000 feet.

Still OK?


Now, I draw your attention to the third large font 2000, the one in between the two previously discussed. It also has a line drawn beneath it, indicating it is a minimum altitude, an "At-or-above" altitude, and it has a lightning bolt-like arrow drawn pointing to the profile immediately prior to the Final Approach Fix, ESKOE. We've already established that we must cross ESKOE at 2,000 feet exactly, and we've established that we must cross FOSOM at or above 2,000 feet. To what point in space does this third restriction apply?

I submit that prior to the FAF, one can be above 2,000 feet, so long as he crosses the FAF AT 2,000'. I don't see the problem, then, in remaining at 3,000 feet while crossing FOSOM, intercepting the glideslope at 3,000 feet, follow the glideslope down to cross ESKOE at 2,000 feet, and so on.

It's not only possible but probable that I have based the thought process on a faulty premise. Perhaps one of those numbers applies to the ILS and one applies to the LOC procedure?


OK, so I got curious enough to dig out some old Jepps...

The Jepps plate for the ILS Rwy 26 says MANDATORY 2000' for the segment between FOSOM and ESKOE, and the "feather" doesn't begin until ESKOE. That makes it pretty clear how I'd be flying it - - descend to exactly 2,000' to intercept the glideslope. The altitude at FOSOM is "AT OR ABOVE" 2,000', so there's some latitude about crossing FOSOM.

An interesting twist in the saga arises when looking at the ILS PRM Rwy 26 (Simultaneous Close Parallel) approach. It's the same except the crossing altitude at FOSOM is MANDATORY 2000'. (The intermediate segment for the ILS Rwy 27L and the ILS PRM Rwy 27L are both "AT OR ABOVE" 3000'.)


Given the reference to the Jepps, then, I'd say you can't use the glideslope until you arrive at ESKOE at exactly 2,000'.


(Now, can somebody tell me what the multiple restrictions on the NOS plate mean?)




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[EatSleepFly]

You have an "at or above" 2000' outside of FOSOM. The next 2000' left of that, is the one pointing to the maltese cross. That applies to the LOC-only approach, since no FAF is depicted on an ILS. That one is just telling you (albeit redundantly) that on the LOC-only approach, you've got to cross ESKOE at or above 2000'. The next one in is the MANDATORY 2000'. This applies to that 1.7 nm segment between FOSOM and ESKOE, meaning that you can't intercept the GS early, at say 3000 and "ride it down," you must fly that segment at 2000'. Above that one, you have the smaller 2000', telling you that GS intecept at ESKOE occurs at 2000'.

That's how I read it. I'm sure I've flown it before, but it's been awhile. Of course, I use Jepps, and if I had them handy, I might have a different opinion.

 

[PIO]

I just ran this approach past a couple of Stand/Eval guys. They say that you can intercept glideslope above 2000 and fly it all the way down as long as you cross ESKOE at 2000.

The at or above 2000 with the lightening bolt pointing at it is the glideslope intercept altitude. The hard altitude of 2000 is a crossing restriction at ESKOE.

 

[Checks]

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[DC8 Flyer]

Dusting off the rust here, bare with me.

The line under the 2000 implies a minimum, not mandatory but a minimum.

The 2000 with lines above and below imply mandatory. With this particular approach I'm betting it applies to a LOC only approach that you must cross ESKOE at 2000'. Why I couldn't tell ya, its Philly, no one knows why Philly does what they do.

If it was intended to make you intercept the glide slope absolutely at 2000' over ESKOE, there would be a 2000 with lines above and below between FOSOM and ESKOE, instead of the 2000 with the below line and the lightning bolt.

I could be wrong though, I will have to look at the Jepps when I get in the airplane tomorrow.

 

[mwmav8r01]

Thanks for all the responces. Except for those who are rude. However this is flight info i had to expect it. The reason i asked the question is because the captain i was flying with just said "fly the GS down from 4000" I didnt quite agree because of the mandatory, it was a VMC day so it wasnt a huge deal. I asked him if he would mind if i joined at 2000 he said that was fine. SO i am glad i did. I must have done it right.



Matt

 

[jumppilot]

I would be at FOLSOM at 2000ft. That is the mandatory altitude.

Pathetic.

 

[JeffSKDTW]

Thanks for all the responces. Except for those who are rude. However this is flight info i had to expect it. The reason i asked the question is because the captain i was flying with just said "fly the GS down from 4000" I didnt quite agree because of the mandatory, it was a VMC day so it wasnt a huge deal. I asked him if he would mind if i joined at 2000 he said that was fine. SO i am glad i did. I must have done it right.

The AIM is your friend.

Section 5-4-5

b. The method used to depict prescribed altitudes on instrument approach charts differs according to techniques employed by different chart publishers. Prescribed altitudes may be depicted in four different configurations: minimum, maximum, mandatory, and recommended. The U.S. Government distributes charts produced by National Imagery and Mapping Agency (NIMA) and FAA. Altitudes are depicted on these charts in the profile view with underscore, overscore, both or none to identify them as minimum, maximum, mandatory or recommended.​

1. Minimum altitude will be depicted with the altitude value underscored. Aircraft are required to maintain altitude at or above the depicted value, e.g., 3000.

2. Maximum altitude will be depicted with the altitude value overscored. Aircraft are required to maintain altitude at or below the depicted value, e.g., 4000. (note--there should be a line above 4000, but will not show up in this forum)

3. Mandatory altitude will be depicted with the altitude value both underscored and overscored. Aircraft are required to maintain altitude at the depicted value, e.g., 5000.

4. Recommended altitude will be depicted with no overscore or underscore. These altitudes are depicted for descent planning, e.g., 6000. (note--there are no lines here)

NOTE-

Pilots are cautioned to adhere to altitudes as prescribed because, in certain instances, they may be used as the basis for vertical separation of aircraft by ATC. When a depicted altitude is specified in the ATC clearance, that altitude becomes mandatory as defined above.




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[EatSleepFly]

The AIM is your friend.

Not really in this case- it didn't do anything to answer the question.

Thanks anyways.