STAR ALT restraints completely ignored

[jrotaetxe 242]

Will try to explain the issue in a step by step basis, from rhe flight planning to the expected termination.

Vers 1.02c

Is a SBGL/SBGR flight, with this flight plan, FL220

SBGL NIND1C W8 NILSA SBGR

Performed perfectly durig the TO. 20 miles before reaching TOD, I began to program my descent. Active runway for landing was 09R, so I choose STAR NILSA3

Here is the process to select...

SBGR arrival page...

Runway 09R in Sao Paulo

NILSA3 Star ...

To the Flight Plan

Preparation of the descent. As I am a lazy pilot, I program the last ILS interception heigth, confident that the computer is going to manage all the "little details" programmed in the STAR. 4700'.

Ok. TOD reached. Commanding the "managed" descent

GURU, the first alt restraint. 15000'. Still above

Oh, oh... LOVE is 13000' and Im already in the 10400' and no magentas...

PONY... 9000' and me in 8200'

UGONO.. FL070, me in 4540 and descending. Once FLAPS2 commanded, she begins to descend slow by slow, no matter the final heigth (4700) you programmed. No loc captured, nothing, but she continues the descent...

To the predictable result

[mopperle 4162]

The questions is always, what type of altitude constraints are there:

- at or above

- at

- at or below

You can get the answer from actual charts.

[jrotaetxe 242]

The questions is always, what type of altitude constraints are there:

- at or above

- at

- at or below

You can get the answer from actual charts.

You are partially right. All the constraints copied (do not know why it takes those, and not the lowest one for each fix) to the MCDU are "at or below" BUT there are also and at the same time, constraints "at or above" for each fix. The straight strategy is take them as "at" and you will be always right.

Anyway, the last two (ZUKE CAST) are AT, and last, but no least, this does not explain the absence of "magentas" in the whole tour.

Enclosed you have the chart, for your reference.

NILSA3.pdf

hope you all will be able to refine this piece os software, because it has an enormous potential.

Regards

[mopperle 4162]

this does not explain the absence of "magentas" in the whole tour.

Not sure what you mean here, but the magenta star in front of an altitude means that the you will met the given constraint. This is different to other aircraft!

[jrotaetxe 242]

Not sure what you mean here, but the magenta star in front of an altitude means that the you will met the given constraint. This is different to other aircraft!

Oh, sorry. I mean there was not any alt constraint in magenta colour in my PFD display. The target altitude has been in bue during the whole approach.

Happy new year (in Spain is Happy new tear, but this is a different matter)

Regards

[jrotaetxe 242]

Researching a little more, entering the STAR, the MCDU catches BOTH constraints (below and above) so there is not problem about the MCDU displaying the constraints. I think this is a good new, as implies the developers want to follow the constraint in the complete sense, respecting the above and the below limit.

So the problem is in another piece of soft, and probably related to the descent path calculations.

Regards

[jrotaetxe 242]

I thik we have catched the fly...

I edited the approach to enter the restraints by hand but one. What happened is she did it wrong with the first restraint (in the MCDU FL150-FL120, which should mean less than 15000 and more than 12000), but CATCHED the next one, inserted by hand (13000), and the subsequent ones...

Next try I will enter the restraint the same format bu the opposite... FL120-FL150, to see what happens. May be is only that the MCDU puts the dual restraints in the opposite way to perform well.

So what is happening is this: When we have "dual" constraints, the FBW only catches the first part of the statement (less than), so it does not respect lower constraints. But if the constraint is simple, understands it is a lower limit, and respects it.

Hope this helps

Regards

[WilliamJSS 16]

So if you want to hit a waypoint at say 12000 or lower, you should put something like 11000 manually in the MCDU to hit at the most 12000?

Seems weird and like a bug, but good to know there is an easy fix for the time being...and would probably take no more than an addition 45 seconds to enter in the MCDU.

[WilliamJSS 16]

We should all be looking and knowing the charts anyways, as I was always taught not to trust the GPS but to actually manually check and make sure it is correct than go off it alone.

[jrotaetxe 242]

So if you want to hit a waypoint at say 12000 or lower, you should put something like 11000 manually in the MCDU to hit at the most 12000?

Seems weird and like a bug, but good to know there is an easy fix for the time being...and would probably take no more than an addition 45 seconds to enter in the MCDU.

Hi, William

Not exactly. For my experience, if you put only an entrance in the alt restraint (say FL150), and you begin, lets say, FL020 and begin your descent programming 4000' as the target, depending of how far you are when you push to start the descent, you are going to hit 15000 sooner, and then maintain 15000 till the fix is crossed, an then continue the descent to 4000), or hit in the target (really difficult, as managed descent does not calculate the "ideal" rate of descent to be there with the required altitude), or later, as single inputs are considered LOWER constraints, so while you keep a heigth bigger than 15000, everything is ok. You can, then, arrive too high to catch the glideslope, but so far, so good.

The problem begins when the restrain means lower (-15000). If there is only an input, every heigth lower than that is legal, so you can dive as much as you are able. Even, you can violate LATER lower restrains and screw the complete approach. For me, this is the first bug, and is a problem because if you enter in a leg with less altitude than the one set in the next fix as lower limit, the system is not going to advise you you are too low...

But the worst is that (as you can see in the chart provided), there are some approaches that "stretches" you between two heigths, telling you must be "Lower than" but also "higher than" (for example, lower than 8000 but higher than 6000). What happens, in this case is that the AXE takes only the first part of the statement (lower than) ad forgets completely there is a second condition, so yo fly without a secure "soil", as the FBW is going to let you go lower than the lower limit.

The way I use is to substitute ALL the retraints manually to legal lower restrains according to the charts and try to be at the indicated limit a little bit before the fix. Using this way, the plane is goig to maintain the required altitude till the fix, and resume the descent automatically once crossed taking the next lower limit, and so on, so you can program the final altitude in the FCU being confident that you are going to be at the right altitude to perform the final.

Sorry for my English, I try to do my best.

Regards

[hud635jk 102]

I can confirm it as well.

It has happened in two flights so far. All with 1.02.

In both flights I ignored the TOD (because it is calculated to be too early after 1.02) and started a managed descent (DES) later (just activated APPR-PHASE to slow down to idle, dialed-down the ALT and pushed it).

The plane will not start to descend, or will descend at a very minimal rate (eg. 300 or 400 ft/min).

[jrotaetxe 242]

I can confirm it as well.

It has happened in two flights so far. All with 1.02.

In both flights I ignored the TOD (because it is calculated to be too early after 1.02) and started a managed descent (DES) later (just activated APPR-PHASE to slow down to idle, dialed-down the ALT and pushed it).

The plane will not start to descend, or will descend at a very minimal rate (eg. 300 or 400 ft/min).

This is another thing, hud635jk.

You are activatig app phase TOO early and then the speed restraint becomes preferential and limts severely the descent rate as IAS must be slow enough to allow you extend flaps.

Descent IS NOT approach. Are different phases and each of them have their rules.

You must enter the app phase while crossing about 4000 feet above the final altitude. Otherwise, you will overshot your altitude 100% of your approaches.

Regards

[jrotaetxe 242]

Not the same but related to.

Impossible to stabilise in a fixed alt once FLAPS2.

[Max Reverse 344]

Not the same but related to.

Impossible to stabilise in a fixed alt once FLAPS2.

You're Not flying in an Managed ALT mode! There has to be a Point behind your ALT on the FCU. If you dont want to fly in Managed ALT mode, but keep the current altidude, then push your V/S knob.(Push to Level Off)

[jrotaetxe 242]

That's the point, Max.

Was not inn mngd- Pushed V/S (you can see +00 in the FCU) and no "dot" in the selected alt, and the VS0 in green in the PFD, but the bird does not obbey...

Almost sure is my fault, but cannot imagine which one.

Thank you for trying to help me. Your aid is much appreciate.

[jrotaetxe 242]

Ok. 1.03 (did not installed 1.03b already) and things are more or less the same from the misinterpretation of the ALT restraints point of view.

Did NILSA3 STAR again and stuck in the same situation.

For example, GURU fix has this restraints:

"At or Lower than FL150" AND "At or higher than FL120"

Consulted the GURU (LSK-R buttons) and I find this 15000-12000.

If I understand well, what this means for the MCDU is that you must fly at 15000 but lower than 12000, which is clearly absurd and could explain the FBW ignoring this kind of restrains.

I'm using Navigraph 1301.

Would appreciate some feedback from Aerosoft to know if this bug is targeted and which would be the forecast.

Regards

[KyleD 1027]

Ok. 1.03 (did not installed 1.03b already) and things are more or less the same from the misinterpretation of the ALT restraints point of view.

Did NILSA3 STAR again and stuck in the same situation.

For example, GURU fix has this restraints:

"At or Lower than FL150" AND "At or higher than FL120"

Consulted the GURU (LSK-R buttons) and I find this 15000-12000.

If I understand well, what this means for the MCDU is that you must fly at 15000 but lower than 12000, which is clearly absurd and could explain the FBW ignoring this kind of restrains.

I'm using Navigraph 1301.

Would appreciate some feedback from Aerosoft to know if this bug is targeted and which would be the forecast.

Regards

What that means is the constraint is basically a block of altitude airspace, meaning you can be anywhere from 12000 to 15000 inside of that constraint. That said, your bus should be no lower than that 12000 feet, but can of course be higher than that up to 15000 feet.

[jrotaetxe 242]

Hello, Kyle.

I did not now that correct name for this kind of restraint is "block" restraint. Perhaps there are thousands of posts talking about the matter and me without realising....

I beg your pardon if such is the case...

Anyway, I interpreted correctly the charts and understood the right behaviour when the bus is to fly in that "bracketed" space, and it is not happening.

Perhaps my english is so poor that I am not being able to express myself, but the point is that the MCDU, when adquires the star from Navigraph presents this in the alt restraint for such kind of block restraints

GURU:

15000-12000

Is that correct?

Shouldn't be 12000-15000?

Is this already detected and being treated?

Regards

[KyleD 1027]

Actually, I think you may be one of the first to ask about these

That looks absolutely correct, and the important thing is if your bus is actually flying the constraint correctly. Also, for the order of the numbers, since you are descending, technically you will reach the higher altitude constraint of 'at or below 15000' first, then you will need to worry about the 'at or above 12000' next, but will take into account both at the same time. (hope that makes sense)

The most important thing to know is if your aircraft complied with that constraint. Reaching that waypoint, was the aircraft flying at or above 12000 and below 15000 at that waypoint as it should have been?

If it did not comply with the constraint, I'll ask for your entire route, so I can replicate your flight and see what's going on.

[jrotaetxe 242]

Thank you very much, Kyle, for your kind response.

All this thread is because it is not flying as (I) expect, so I would like somebody wiser than me states if it is wrong or not.

Here is the FP you request. It is a nice one to fly (Brazilian coast) and takes an our more or less.

SBRJ (NIND) W8 PUBTI NILSA (NILSA) SBGR

In brackets are SID and STAR selected. Choose a wind to use RWY 27L. The STAR NILSA can be NILSA4 or NILSA6, but it does not matter. Act as if you were a lazy pilot and program your descent with the final 4800 feet to intercept the ILS Z 27L in SBGR, relying the constraints will help you in your approach.

You have a set of screen captures in top of the thread. Choose SBRJ because is a nice take off, and please, forgive me for the error in the first post. is not an SBGL/SBGR FLIGHT, but a SBRJ/SBGR... Interesting also, as the RWY in SBRJ is VERY short.

Regards

[KyleD 1027]

Ahhh, I actually missed that screenshot. It looks perfectly okay, and I say that because you are still 17.4nm from the waypoint and the constraint, and you are only at 15,200 feet, which tells me that by the time you actually do reach the constraint at GURU, you will be in that block constraint. So, it looks like it is working fine to me.

If you happen/want to do that flight again, take a screenshot just like you did, but take it right when you are at the GURU waypoint, post it here and I'll tell you if it is right or not, and explain why or why not. You don't have to, just saying that if you do decide to do that flight again. In the meantime later today I'll fly that route myself and see what happens.

[jrotaetxe 242]

For Kyle

Discovered...

These two will show you the problem and save some of your time flying other interesting places in the planet...

This is the vert revission of SEPKA fix. We can see the -FL21 in the alt restraint, so the "minus" sign clearly states "At or less than". In this case, les than 21000 ft. As a conlussion, sign + or the absence of sign must imply "At or over"

So far, so good

Lets examine GURU vert revision:

We see FL150-FL120.

So applying the lesson already learnt, this states "At or over 15000 AND At or less than 12000" which is absurd.

And this can be the reason why the whole restraint set fails. All the subsequent fixes are the same.

To finish, a couple more to clarify the problem

Crossing GURU and established below 12000 (11900)

Regards

[KyleD 1027]

So applying the lesson already learnt, this states "At or over 15000 AND At or less than 12000" which is absurd.

And this can be the reason why the whole restraint set fails. All the subsequent fixes are the same.

Crossing GURU and established below 12000 (11900)

Ok, like I said before, the constraint is "at or below 15000", and "at or above 12000", not opposite eachother like you said above. So, you need to be anywhere between 12,000 feet and 15,000 feet, not outside of that.

As for your last screenshot and the one before it, it looks like you are using a selected altitude, and not a VNAV altitude. I can see that since your altitude arrow is blue and not magenta. You should just leave it in managed DES and see what happens.

I'll still give this flight a go and see what comes out.

[jrotaetxe 242]

Ok, like I said before, the constraint is "at or below 15000", and "at or above 12000", not opposite eachother like you said above. So, you need to be anywhere between 12,000 feet and 15,000 feet, not outside of that.

... Then we must admit there is an unconsistency in the way the MCDU presents the restraints, as in the first restraint (SEPKA) the minus sign states "At or less", but in GURU the minus sign states "At or over"...

As for your last screenshot and the one before it, it looks like you are using a selected altitude, and not a VNAV altitude. I can see that since your altitude arrow is blue and not magenta. You should just leave it in managed DES and see what happens.

But that's the point, dear friend. In all the trip I have been using managed mode (pushing the ALT. Never pulling it). The fact the Alt in the FDU and the arrow are in blue proves I have been able to cross the restraint prior to crossing GURU (GURU still not crossed. It is in white already) without any indication.

Thank you again for your patience.

Regards

I'll still give this flight a go and see what comes out

[KyleD 1027]

I'll still give this flight a go and see what comes out

Ok, before you do that, please apply this hotfix: http://forum.aerosof...ce/#entry447207