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If ATC gives me a clearance to cross a fix at a specific altitude or a descent at pilot's discretion and I read back the clearance, is my readback considered the report specified in the AIM, or do I have to inform them when I actually start down?

AIM 5-3-3. Additional Reports

a. The following reports should be made to ATC or FSS facilities without a specific ATC request:

1. At all times.

(a) When vacating any previously assigned altitude or flight level for a newly assigned altitude or flight level.

...

An Example - Say that a pilot is flying at flight level 340 100 NM from Wilmington VOR and gets the following clearance:

ATC: N1234, cross Wilmington VOR at flight level 240
Pilot: Cross Wilmington VOR at flight level 240, N1234

or

ATC: N1234, descend at pilot's discretion to flight level 240
Pilot: Descend at pilot's discretion to flight level 240

It's a little early to start down since we want to stay high for fuel efficiency, so the pilot decides to wait until 30 NM from the VOR to start down. When they reach that point, are they required to inform ATC before starting the descent or are they considered to have reported the descent earlier?

I hear pilots that do it both ways and each camp is pretty emphatic about it....

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  • $\begingroup$ They are usually giving you a descent clearance before that, but could be at pilot's discretion, in which case I am not exactly sure. We're talking IFR right, and not VFR who's about to enter a B or something? $\endgroup$ – falstro Dec 25 '13 at 17:07
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    $\begingroup$ @roe: Yes, IFR. It is actually very common for them to have us cross a fix (or "cross 40 miles North of" a fix) at a specific altitude and leave it up to us as to when to start down. The same question can be asked of a descent a pilot's discretion however, and I will add that to the question. $\endgroup$ – Lnafziger Dec 25 '13 at 17:57
  • $\begingroup$ It certainly can't hurt to call again, and it adds to the level of safety. In flying, I choose pedantry over brevity any day. $\endgroup$ – Jonathan Landrum Dec 26 '13 at 21:01
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    $\begingroup$ @JonathanLandrum: I agree that it can't hurt, but I am trying to determine the actual requirement. Sometimes, in very busy airspace it can be hard to squeeze this call in, and if it isn't required I would sometimes skip it. I also get varied reactions from controllers, sometimes feeling like I am bothering them with a call that isn't required. $\endgroup$ – Lnafziger Dec 27 '13 at 1:10
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I’ve been a controller in both the en route and terminal environments. While I agree with your interpretation of the AIM that it appears to be required, reorting leaving your altitude is not expected and I did not usually hear it done.

To give the perspective from the other side of the mic, an altitude crossing restriction is functionally equivalent to a pilot’s discretion climb/descent to that point. ATC will protect all altitudes between your current one and the restriction, and you are free to hit that restriction as you see fit (barring the violation of other regulations, of course). You may not return to a previously vacated altitude as part of your climb/descent, but you may level.

You are also correct in that it can tie up the freq as an “unnecessary” call, but if you are unsure, better to over inform rather than under inform.

Incidentally, very few controllers read the AIM. The 7110.65 takes precedence, and I’ve actually had a supervisor yell at me for referring to the AIM once. I know, I know.

So, legally, it should be done. In practice? Unnecessary and I preferred that it not be done when I was working.

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    $\begingroup$ It's great to see a controller answer this, welcome to our site! $\endgroup$ – Lnafziger Feb 8 '18 at 18:01
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Short Answer

No, but you should.


Long Answer

I see two questions which I will answer—or attempt to answer—each in turn. Firstly, from the title:

Are you required to report leaving an altitude if you have been given a crossing restriction?

And secondly:

If ATC gives me a clearance to cross a fix at a specific altitude or a descent at pilot's discretion and I read back the clearance, is my readback considered the report specified in the AIM, or do I have to inform them when I actually start down?


To the first question: no, you are not required to report leaving any altitude. Those items that must be reported are listed in 14 CFR 91.183, including:

(a) The time and altitude of passing each designated reporting point, or the reporting points specified by ATC, except that while the aircraft is under radar control, only the passing of those reporting points specifically requested by ATC need be reported;

(b) Any unforecast weather conditions encountered; and

(c) Any other information relating to the safety of flight.

Leaving an altitude is clearly not listed here. However, as you note, the "leaving an altitude report" is found in the the Aeronautical Information Manual (AIM):

5-3-3. Additional Reports

a. The following reports should be made to ATC or FSS facilities without a specific ATC request:

  1. At all times.

(a) When vacating any previously assigned altitude or flight level for a newly assigned altitude or flight level.

When the FAA means for something to be mandatory, the word "must" is used in regulation. However, the FAA's Plain Language Program Manager helps us understand the use of "should" as "meaning optional but implies that the writer recommends and advises the reader to use that option." Moreover, given that the AIM is itself not regulatory, we can interpret the plain language of the above excerpt at face value: the report should be made, but is not mandatory or required.

Though optional, the report is generally a good idea, recommended, advisable, and in keeping with best practice. You should give that report, even if the pilot flying gives you a funny look. I too hear some pilots give the report, and I find there are perhaps more that omit it. I have come to consider the making of that report to be one of many marks that indicate disciplined airmanship.

From a more subjective standpoint, I acknowledge that there may be valid reasons to omit the report. Indeed some jurisdictions explicitly do not require the report in radar environments unless requested by ATC. From personal experience, controllers generally seem uninterested in a vacating altitude report.

But, the FAA says you should make the report.


To the second question: no, probably not. If you readback a clearance for descent at pilot's discretion, that is a clearance readback, not a vacating altitude report. Moreover, if you receive that clearance and then commence the descent at some other time, the readback is not satisfying the "when" part of "when vacating any previously assigned altitude".

In your specific example of a descent clearance received and readback 70 NM prior to commencing descent, that readback would not comprise a report made when vacating FL340.

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AIM 5-3-3. Additional Reports

a. The following reports should be made to ATC or FSS facilities without a specific ATC request:

1. At all times.

(a) When vacating any previously assigned altitude or flight level for a newly assigned altitude or flight level.

Emphasis mine. The phrase 'when vacating' is pretty unambiguous.

Edited answer to better respond to your comment. Previous answer below.


The AIM explains the purpose of readbacks in 4-4-7b:

ATC Clearance/Instruction Readback. Pilots of airborne aircraft should read back those parts of ATC clearances and instructions containing altitude assignments, vectors, or runway assignments as a means of mutual verification. The read back of the “numbers" serves as a double check between pilots and controllers and reduces the kinds of communications errors that occur when a number is either “misheard" or is incorrect.

Although this is stretching, I find it easier to believe that a readback does not qualify and you should call again when you actually start down.

Furthermore, the AIM references FAR 91.183, which says that the pilot of an aircraft operating under IFR must report as soon as possible

(c) Any other information relating to the safety of flight.

If you figure altitude changes qualify as safety of flight information, it's probably not a bad idea to make a second radio call.

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    $\begingroup$ So the answer is "no", it's not required. The AIM says you should notify ATC, but there is no requirement to do so. $\endgroup$ – David Schwartz Mar 8 '17 at 19:31
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Absolutely report leaving the previously assigned altitude. And this applies equally when receiving a clearance "cleared for the approach." I recall once being cleared for an approach from a holding pattern. Planes were stacked above me. I wanted to maintain my holding altitude until over the holding fix. Thus I did not say, "Leaving 2000 feet." I left that altitude quickly when approach control told the plane above me to descend to 2,000 feet.

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  • $\begingroup$ You answered in the affirmative, meaning, I understand, that a pilot is indeed required to report vacating. Can you provide a reference? $\endgroup$ – J Walters Jan 30 '17 at 2:33
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In the US... Under radar contact the leaving level phraseology is not expected nor needed by ATC. What they do need is you tell them what altitude you are at (plus climbing/descend to) when you check in. The leaving level is mandatory when flying without radar contact. But AIM tells us to do it anyways. I listened in nearly 100 hours of recent flying (Premier 1 Driver on youtube), and he never uses leaving level, ATC never asks him to. Other pilots don't use it either. It is confusing because the AIM teaches us to do it, as well as my instructor did when I got my IFR rating. And it used to be SOP even in radar contact a long time ago. I'm PPSEL IFR USA. But I haven't flown in 15 years.

Ok, I can't add a comment to user331's answer which conflicts with mine, so let me ask here. Go out and listen to tens and tens of hours of ATC comms. You will find out that what's being done is reading back the descent clearance. When the descent is immediate that creates the impression that the purpose of the readback is to confirm leaving that level, but when its a PD or a descent with a constraint that can be delayed, you will find the pilot doesn't come back and informs leaving later. So what I said matches real world actions.

If ATC wanted us to report actually leaving the altitude, they would be chastizing every body for not reporting when the altitude change is delayed. The practical reason is simple, under radar contact ATC can see your descent on radar. Without radar contact its a very different deal, ATC cannot see your transponder altitude so they cannot confirm you are descending, vacating your original altitude so actual confirmation is required.

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