What exactly is an altitude restriction (Jepp)?
 

Approach plates for LEMI (RMU, Murcia, Spain).

Was cleared direct to DIXIR descending to FL110 from a WPT 40-50nm North (prior to STAR). 10nm prior to DIXIR controller (no radar) instructed to "descend according to procedure" and cleared us for ILSRWY 23. PF dialled in 4100 and we crossed DIXIR at about 6000ft. The "Non-Radar" controller than asked us to confirm our altitude and advised "there was a published restriction at DIXIR".

I could be having a brain fart but according to what logic is FL75 an altitude restriction at DIXIR? On Jepp, an altitude restriction is in BOLD and bounded by an Above or Below line. FL75 to me is the minimum altitude between XOLSI and DIXIR. Not a restriction. And we were cleared direct to DIXIR from 50nm out. Stupidly, even the ILS approach plate does not have a minimum altitude for DIXIR.


https://cimg1.ibsrv.net/gimg/pprune....8b7c7d0fa8.png


https://cimg3.ibsrv.net/gimg/pprune....0e10e4678d.png

So far I had a rule to have a vaild reason before descending below a minimum charted altitude - FL75 in this case. When the controller informs 'non-radar' that goes with triple checking.

Not sure what your PF's logic is and looking for reasons to support it reads awkard. Dare to post the AIP?

Could be a restriction from a NOTAM, hence you don't have it in your charts.

From the AIP:


https://cimg1.ibsrv.net/gimg/pprune....8fcdf0e652.png
https://cimg2.ibsrv.net/gimg/pprune....69425209f5.png
https://cimg3.ibsrv.net/gimg/pprune....f9b773dc5e.png

Appreciated, thank you. FL75+ charted before DIXIR, right?

Southern side has exactly at FL90 until R-051, which is not relevant but the awareness should raise questions about airspace rules and complexity.

Yes, although it appears to me at least to be associated with the procedural segment and not DIXIR itself, which is the point of contention I suppose. Here is a Spanish AIP example where the restriction is clearly applicable at a fix:
https://cimg4.ibsrv.net/gimg/pprune....985dc0954e.png

100% agree on the principle of erring on the side of caution and querying with ATC in such cases though.

Telkon, you are abosolutely right. As you suspect, the procedural segment restriction in front of a waypoint is good enough instruction in case of a DCT to that waypoint,
- in the absence of any other grounds for a lower descent
- when told to follow the procedural alts

But that is just a personal technique (?).

Easy for a desk&chair debate, real life airborne it is harder to keep thigs simple at all times.

Please don't shoot me down, not a commercial pilot just a lapsed PPL with IMC but I still find it interesting reading these plates and trying to understand what they're saying, sad I know, but that's the way I am.

Could the confusion come from the top most AIP plate which shows an approach to DIXIR from the NE, from XOLSI, which has a lower limit of FL75?

DIXIR has a crossing ht of FL75 which will remain. Direct to clearance is for lateral path. Lower descent can only be at DIXIR or earlier if cleared by ATC. Even with cleared for ILS and on GS terrain clearance is not ensured below the step down fixes. Refer to FAA InFO 11009.

CW247 You mentioned being cleared for an ILS Z runway 23. The plate shown is ILS runway 23. Is there another approach plate for this runway?

In the absence of a NOTAM, this is a bit of a gotcha. Normally, a crossing restriction would be formatted as you describe. In this case, 7500 is the MEA for the segment between XOLSI and DIXIR, so you would be expected to respect it.

https://ww2.jeppesen.com/wp-content/...ion-Charts.pdf

Page SID/STAR-4

I don't see FL75 as an altitude restriction being cleared direct to. FL75 is a minimum for a procedural transition. If non-radar I would expect off route descent clearances based on distance from the fix/beacon. Even the Italians used to ask for distance before issuing descent clearances, felt reassuring.

Sorry, approach was ILS 23, not a Z one. There are several restricted areas around the airport which may be activated by NOTAM. We didn't pick up on anything that day. Grid MORA where DIXIR lies is 7100. We definitely could've erred on the side of caution but once again I find myself challenged by an aviation world where there lie nothing but traps. :ouch:

Edit to say that DIXIR is 23 miles from the threshold, to cross DIXIR at 7500 would be a little sporty and we had a tailwind that day.

I agree with controller, a restriction between two points should be adhered to at the final point.

That's how airbus code it in FMS too.

I could be wrong but the FMS coded constraint (+FL75) is only there because it is inherited from the original route so I don't think Airbus explicitly coded it for a direct routing. As we were not flying from XOLSI to DIXIR and were on a direct routing. A better statement from the controller would've been "maintain FL75, after DIXIR cleared ILS 23". From a non radar controller, that would be the better thing to say. Instead they leave you in no mans land where you have to consider so many other aspects of your performance in order to make the glideslope.

Why then VILAS do some charts bother to show a bounded constraint, and some don't. If it's that important? ....

Except he was not flying between them two points. Why should FL75 be adhered to and not FL90, as is published if you come via the arc on the ILS -plate?

Poor charts, poor ATC instructions. The MSA is a good safety net to fall back on. While not an operational altitude as such, it's often easier than trying to figure out what ATC wants in broken English.

Good question ?

If you were cleared to FL090 on the arc and cleared for the approach, how would you know when to descend below FL090 ?

The side of caution would not be erring, but prudent safe choice.

Going below charted altitudes with a specific prior clearance to observe the procedural alt was the error. To be perfectly honest, I could clearly see a day where I might do that as well, unintetional as was your case. And kudos for discussing it.

The issue at hand is that your flight fell into a non-charted, off-procedure gap. Hence the differing opinions you read, describing what needs to be done on the different published segments and procedural tracks. But you'd never have had an issue if flying along one of those.

+ Under vectors, the ATC is responsible for minimum altitudes.
+ For a DIR TO after vectors, ATC is responsible for the last altitude to rejoin the procedure
- However in your case, you got an off-route short-cut without radar control. What then?

ell, the ATC is not responsible for your altitude and hence his hint to follow the procedure but at the same time you were not literally following any charted route. That combined with ommiting the info from the arrival chart and diving straight for the approach plate caused the mixup.

To me it seems we're looking here for a (chart-based) solution that does not exist. It's not about Jeppesen's presentation of altitudes, not about information provided in the AIP (yet again more rich than Jepp, not a real factor thouhg). What needs to be done in fact is to build a solution from the pieces that do not really apply exactly to your routing and clearance, becasue for those there is no specific information at all. Yes, that was a no-mans-land, but the difference between an aviator we all claim to be and an autopilot is to know which way is Mordor no matter the terrain and surroundings.

a) Routing to DIXIR - yes
b) Are there any tracks to DIXIR - yes
c) Do those tracks have a ALT limitation - yes
d) Are the charted tracks inbound DIXIR near (angular displacement) to the current routing - yes
= building a solution = decide to observe FL75+ before DIXIR published nearby (and possibly seek verbal clarification if lower is needed).

Not sure if this is educative-rethorical so leaving that unanswered not to spoil the magic?