Tummy

I was receiving vectors for the ILS Rwy 13L at JFK. We were at 2,800' MSL on a 120 heading, and we were cleared to intercept the localizer. Our heading would have us intercept the localizer about 1 mile outside of TELEX.

https://skyvector.com/files/tpp/1511/pdf/00610IL13L.PDF

ATC instructed me to "Cross TELEX at or above 2,100', cleared for the ILS Rwy 13L." I used FLCH to start down to 2,100', and at about 2,500', my Captain said, "We're below MSA. There are some big buildings down there. Don't descend." Then, he reached up and hit ALT HOLD.

I was under the impression that the instruction to cross TELEX at or above 2,100' meant that I could start down to 2,100'. After we landed, the Captain said that I needed to stay at 2,800' until intercepting the localizer. I'm having trouble finding the reference. Does anyone know the answer and/or where I should look?

4V14T0R

Were you instructed to maintain 2800 until established?


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Hrkdrivr

CFR 14 §91.175, Takeoff and landing under IFR, paragraph (i) - " When operating on an unpublished route or while being radar vectored, the pilot, when an approach clearance is received, shall, in addition to complying with §91.177, maintain the last altitude assigned to that pilot until the aircraft is established on a segment of a published route or instrument approach procedure unless a different altitude is assigned by ATC. After the aircraft is so established, published altitudes apply to descent within each succeeding route or approach segment unless a different altitude is assigned by ATC."

Cleared for a visual approach in VMC, different animal.

cencal83406

Last assigned altitude would be at/above 2100'. Would it not?
Or am I thinking of a clearance like "maintain 2100 until established"

An at/above strikes me as a visual clearance unless they are keeping other vector traffic clear as in times of low pressure.

Hrkdrivr

Given only what the OP said I don't think so. I think the last assigned altitude was 2800.

VMC/IMC doesn't matter if he's still on an IFR clearance.

Simple solution, as always, is just ask...can I descend now?

Adlerdriver

ATC can put you below the MSA if their MVA allows. I can't find a good chart of the NYC area min vector altitudes so it's hard to verify what ATC could put you down to out there.

That said, that doesn't sound like a normal clearance on a vector to an ILS. Usually they give you a "maintain _____ until established". A 120 heading for a 135 inbound course, is kind of a shallow intercept. Is it possible you were already inside 10 degrees off the LOC and technically established (or appeared that way to ATC)? It seems like they give a vertical clearance limit (like cross TELEX at or above 2100) when clearing someone for the approach who is already established on a segment of the approach. Otherwise they use the terminology I previously mentioned.

The situation sounds confusing enough that I think you guys needed to clarify your clearance. You don't want to assume and it was good SA on the Captain's side to speak up considering the size of some of the buildings out that way. However, if you were going to intercept the LOC only a mile outside TELEX, staying at 2800 wasn't a good option either. The 2100 at TELEX appears to be pretty close to 3:1 based on glide slope intercept at 1500 only two miles later. If you had stayed at 2800, you would have set up a scramble to get down and capture the g/s.

It would be interesting to hear an ATC persons take on this.

Hrkdrivr

Good point. Maybe there's more to the setup we don't know yet.

In any case, push it 5 miles outside TELEX on a 30 degree intercept, the book answer remains the same.

Adlerdriver

One other minor technique issue: Would you consider a different vertical mode than FLCH for a low altitude descent? Don't know your exact equipment (777 uses more advanced logic) but earlier model Boeings descend in idle always when using FLCH.

I usually try to avoid an idle descent when below about 3000 AGL unless absolutely necessary. Seems like maybe a more controlled descent using v/s might have been a better technique, especially for only 700 feet to lose. Then maybe you intercept the g/s on your way down and never have to level off (assuming you get onto the LOC). Otherwise you get down almost immediately, have to level off and drive only to recapture descent and start down again. Just a thought.

Tummy

No. 2,800' and 120 heading cleared to intercept the localizer. Next clearance, "Cross TELEX at or above 2,100', cleared for the ILS Rwy 13L." I suppose I thought the direction to cross TELEX at or above 2,100' gave me protection to begin descent to 2,100' at that time, because clearance to maintain 120 heading, intercept the localizer, cleared for the ILS Rwy 13 would still have made 2,100' a hard minimum at TELEX.

We were on a 120 heading, but the winds were pretty stiff. About 150 at 50, so our ground track was probably in the 100 to 110 range. I'd also be interested to hear an ATC person's opinion. I was under the impression that I was protected by MVA from the "cross at or above 2,100'" clearance, but I've been wrong before.

Here's the best JFK MVA chart I could find.

https://www.faa.gov/air_traffic/flig...K_MVA_2013.pdf

Tummy

That's what I thought at the time. Now, I'm not so sure.