Non-precision approach from a higher-than-published platform altitude

[amark16]

Hi all,
Wanted some input on the following scenario and how to handle on an A320, or any other modern jet for that matter:

We are being vectored for a non-precision approach such as VOR or LOC. The published platform altitude is 2000', the FAF is at 5 nm and the descent angle is 3.00 degrees.
ATC leaves us at 2500' and does not clear us to the platform altitude of 2000', even if requested. When and how do we start the final descent:

A. Start the descent at published FAF of 5 nm, but use a higher descent angle initially, say 3.50 degrees to catch the proper vertical path.
B. Start the descent before you reach FAF, say at around 6.5 NM using a 3.00 path?
C. None of the above (Insert correct answer here)

Thanks!!

[safelife]

In EASA land CDFA technique is now compulsory.
So for us, extend the final outwards und upwards.

[Sidestick_n_Rudder]

Technically both A and B are correct. A non precision approach does not care what glide path you are using, as long as you fly the correct lateral path and stay above all minimum altitudes.

However, optoon A is more complicated, error-prone and may lead to several problems, like unstable approach by being too high.

Option B is ok, but still a bit difficult, as you need to hit the FAF at the right altitude in a continuous descent. Passing FAF above platform altitude is ok, but can lead to the same problems as in option A. Passing FAF BELOW platform altitude is a no-no!

Option C would be to descend to platform altitude before reaching FAF and start final approach at the FAF. That’s by far the simplest way and avoids the pitfalls of options A and B.

As for the ATC clearance. Once you are cleared for approach AND established on a published segment of the approach (eg. on final course, before FAF). You may descend as you like, to the minimum published altitudes for the given sector. There’s no need to obtain further clearance for lower altitude from the ATC. Approach clearance is all you need...


@ Safelife - CDFA means Continuous Descent FINAL Approach (my bold), so it only applies after passing the FAF. It’s a common misconception that you have to start it earlier and can lead to several problems, like eg. getting it wrong and passing the FAF below published altitude.

[stilton]

Never heard the expression ‘platform altitude’ before


I assume this is the charted altitude crossing
the FAF ?

[SaulGoodman]

On jets don’t dive and drive, at least not in EASA land. Extend it outwards and upwards as mentioned before. It is not that hard. If you have profile or vnav all you need to do is monitor if you haven’t you add 1 mile for every 300’ and asjust ROD when needed. It really doesn’t matter if you do it in Profile and nav or hdg sel and v/s, as long as you do it correct ;)

[amark16]

Thanks for all the replies. This happened to a friend of mine recently on a sim assessment. He was asked to intercept the final approach track from 2500 instead of the published 2000. The examiner playing the ATC role didn't give him further descent but cleared him for the approach. He opted for a steeper initial descent from 2500 at the FAF, and after quite a struggle, managed to get on the correct profile and stabilize himself. But indeed, it's much harder work to manage the energy so I too think it's better to extend outwards and upwards. I mean there's no regulation prohibiting you to do this as far as I gather.

[Sidestick_n_Rudder]

This happened to a friend of mine recently on a sim assessment. He was asked to intercept the final approach track from 2500 instead of the published 2000. The examiner playing the ATC role didn't give him further descent but cleared him for the approach.

That sounds more like an excercise to check if the pilot under asessment understands what approach clearance is and/or is able to calculate 3 deg path.

Having said that, I still emphasize that CDFA concept is valid from FAF onwards. Before the FAF you are free to descend as you please, as long as you stay at or above the min published altitudes. Both level flight and constant descent before the FAF are perfectly 'kosher', with the latter being a bit more tricky than the former, requiring a bit of practice and vigilance...

[Vessbot]

That sounds more like an excercise to check if the pilot under asessment understands what approach clearance is and/or is able to calculate 3 deg path.

Having said that, I still emphasize that CDFA concept is valid from FAF onwards. Before the FAF you are free to descend as you please, as long as you stay at or above the min published altitudes. Both level flight and constant descent before the FAF are perfectly 'kosher', with the latter being a bit more tricky than the former, requiring a bit of practice and vigilance...

This, with emphasis on the part I bolded. Now I'm tempering the strength of my words due to any subtleties I'm not familiar with European procedures, but from what others have posted it seems that it's the same as FAA-land: that an approach clearance is a clearance to descend to the minimum altitude for any segment that you're established on. So the pilot in the situation was cleared to 2000 once established on the leg prior to the FAF, even though that wasn't explicitly said. So his choice to stay at 2500 was an inappropriate one that set him up for an unstabilized approach, and hopefully lead to an illuminating debrief.

... all assuming that the procedure is indeed the same as in the US.

[FlightDetent]

Agreed. Clearance for Approach is all the way down to the runway. And approach starts passing IAF.

1) descend to 2000 before the FAF (and fly a bit level before reaching that position)
2a) descend to 2000 immediately with a smart rate chosen to reach FAF and 2000 concurrently
2b) wait until intercepting "extended" 3° profile and descend with a fixed path via FAF passing it at 2000.

3) staying high until FAF is incompetence (even if confusion driven).

[jimtx]

This, with emphasis on the part I bolded. Now I'm tempering the strength of my words due to any subtleties I'm not familiar with European procedures, but from what others have posted it seems that it's the same as FAA-land: that an approach clearance is a clearance to descend to the minimum altitude for any segment that you're established on. So the pilot in the situation was cleared to 2000 once established on the leg prior to the FAF, even though that wasn't explicitly said. So his choice to stay at 2500 was an inappropriate one that set him up for an unstabilized approach, and hopefully lead to an illuminating debrief.

... all assuming that the procedure is indeed the same as in the US.

If you are established on a segment: https://www.aopa.org/news-and-media/all-news/1998/june/pilot/landmark-accidents-cleared-for-the-approach

Maybe the examiner left him at MVA and wanted to see if he would descend before established on a segment. BTW, back when that accident happened my military training was that "cleared for the approach" was clearance to initial approach altitude. That got changed.

[A Squared]

Technically both A and B are correct.

A may be "correct", whatever that means, but it's pretty suboptimal. The proposed 3.5 degree descent angle won't work in the described scenario, it would take a 3.77 degree descent angle to descend to the airport, considerably more to "catch the proper vertical path". For reference, a 3.77 degree descent angle is steeper than would be normally permitted for approach design for Cat D and E by the US TERPS and right at the limit for Category C.

[roulette]

A may be "correct", whatever that means, but it's pretty suboptimal. The proposed 3.5 degree descent angle won't work in the described scenario, it would take a 3.77 degree descent angle to descend to the airport, considerably more to "catch the proper vertical path". For reference, a 3.77 degree descent angle is steeper than would be normally permitted for approach design for Cat D and E by the US TERPS and right at the limit for Category C.

Under ICAO PANS-OPS criteria for instrument flight procedure designs for just about everywhere except the US, 3.5° is the max descent angle for Cat C, D & E aircraft, except where they have specific airworthiness &/or ops approvals otherwise. Similarly, 3.72° is the max descent angle for Cat A & B aircraft, except where otherwise authorized.

It's my understanding that the CDFA can actually be interpreted to extend beyond (prior) the FAF - as it is in practice done in the EU now. Like the IATA CANPA, basically if you're in landing config, you're better off to follow the CDFA/CANPA techniques. And as someone else said, these days in any modern aircraft you can use the avionics to help guide you down and the PNF does the dist/alt checks and readouts. Many charts these days provide dist/alt tables for this purpose and they generally extend beyond (prior) the FAF so that by the time you intercept the FAF (even from say 2NM prior) you're already established on the published descent profile for the final.

Re the original question, starting higher than the published descent gradient (and anywhere near max certified descent angle for the acft is not safe - especially if you don't take into account potential hot temp correction issues - even with a 5NM final (worse if the final is shorter, obviously). This is the kind of behaviour (different reasons why) that for example led to the Korean Air unstabilised APCH into SFO a few years back and ultimately a highly undesirable landing (accident). So Option A is really quite suboptimal.
And ultimately if the PIC is not happy, tell the ATC unable and seek clarification or new instructions.

[Gray 14]

Sector altitude till final then descent to FAF min then descend to MDA.

[Check Airman]

A few comments on this one

1. Most sim instructors (in the US) use RT that would make your average ATC weep. As such, I've seen them give very confusing clearances that have led to the student botching the manoeuvre.

2. Without knowing if your company has any VS limits below certain altitudes, I can't say that option A is wrong. The altitudes on the charts are typically minimum, and not mandatory altitudes. Crossing the FAF at 2500 isn't my preferred technique, but it's not objectively wrong.

3. My preferred technique would be option B, if staying at 2500. Just start down a 3 degree path early.

[hans brinker]

Like most here have said, descend to 2000' when established on a published segment of the appraoch that has a minimum altitude of at least 2000'. If the instructor cleared him direct to the FAF, an maintain 2500' he would not have the option of descending until passing the FAF. In this case the prudent option would be to refuse the approach clearance unless the controller can provide a lower altitude or a longer lineup so as to get established on a published segment earlier. The reason I emphasize the published segment part is that I used to go to Leon (Spain, if I remember correctly), there was a holding pattern on the OM aligned with the final course, but no extended final and no DME, and there always was a discussion if you were being vectored in above the OM crossing alt when you could start your descend (we weren't allowed to use the ILS, just the OM/NDB). I would convert the max holding speed to 1 minute ground distance, and use the GPS to start my descend. As we weren't approved for GPS approaches, only arrival, I am sure that although it worked, it wasn't necessarily legal.....
If you would dive and drive the NDB approach you would be 5 miles out at 400' AGL!!

[A Squared]

If the instructor cleared him direct to the FAF, an maintain 2500' he would not have the option of descending until passing the FAF.

That's correct, but in line with your observation about poor quality simulated ATC from sim instructors, that would not be correct vectors for an approach. By ATC's procedures they are supposed to put you on an intercept for the intermediate course that will intercept a certain distance outside the faf, and less than some maximum intercept angle. At least by US ATC specs.

[aterpster]

If you are established on a segment: https://www.aopa.org/news-and-media/all-news/1998/june/pilot/landmark-accidents-cleared-for-the-approach

Maybe the examiner left him at MVA and wanted to see if he would descend before established on a segment. BTW, back when that accident happened my military training was that "cleared for the approach" was clearance to initial approach altitude. That got changed.
I was flying the 727 at TWA when TWA 514 occurred. I was an ALPA investigator assigned to the NTSB investigation. In that era TWA taught when vectored to the final approach course you could descend to the highest altitude shown in the profile view, which is normally the intermediate segment altitude. The procedure in use was new (some 5 months old at the time) and it was defectively designed by the FAA. Round Hlll intersection was the intermediate fix and should have been in the profile view. The three initial segments shown should have all been 3,700 to provide a uniform altitude at Round Hill. Had Round Hill been in the profile view, the accident would not have happened.
https://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/492x906/twa_514_jepp_chart_ebfbc01ec674d90fe216bf70534e702279897f92. jpg

[jimtx]

Rereading some of the TWA 514 stuff reminded me of a pet peeve regarding descents. A few guys had no thought process for descent planning and there we would be in the Andes bouncing along at MEA xxx miles from the airport. Most of us had a plan and when cleared early would request PD or shallow the descent with ATC approval.

[aterpster]

Rereading some of the TWA 514 stuff reminded me of a pet peeve regarding descents. A few guys had no thought process for descent planning and there we would be in the Andes bouncing along at MEA xxx miles from the airport. Most of us had a plan and when cleared early would request PD or shallow the descent with ATC approval.
A friend of mine flew to South America in the 747. His company policy was no off airways below FL 250 and don't accept either en route or terminal radar vectors.

Remember the EAL 727 that plowed into one of the mountains east of La Paz?