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[A320Family] Managed speed problem

Postby Darkriser » Tue Aug 22, 2017 10:48 am

Today I decided to try the managed speed feature for the first time.
There's either a bug or I'm doing sthing wrong.

pre-conditions:
- one of the A319's, but the same applies to all other family members
- standard FOB 12000lbs, GW 130000lbs
- MCDU: CI 40, FL330
- AP panel: push SPD and NAV buttons to let AP do all the business
- initial speed set by autopilot was 157

climb phase (seems perfect to me):
- after lift-off I selected AP1
- 157IAS was maintained until 3000ASL, then 250IAS commanded (automatically)
- after crossing 10000, 300IAS was commanded
- as ALT increases, IAS decreases and MACH increases slowly:
- FL180/290IAS/M.61
- FL250/280IAS/M.68
- FL300/275IAS/M.73
- slightly before reaching FL300, the speed AP dial automatically switched from SPD to MACH

cruise:
- FL330
- M.75, GS/TAS 402, 265IAS, headwind around 40kts, maybe a bit slow, but still ok...

descend (not as expected):
- FOB 7400lbs, GW 125400lbs
- dialed 10000 and pressed the ALT knob
- as expected, IAS increases, MACH decreases slowly UNTIL M.703
- once MACH 0.703 reached, it remains set constantly, AP speed dial still switched to MACH!
- result - the plane descends, IAS increases (as M.7 is constant) up to 360+IAS (at around FL150)....where I manually leveled off and slowed-down the plane

I performed immediately another climb to FL330 followed by a second descend to FL13:
- during the climb, MACH was selected (at FL around FL150 I expected SPD instead of MACH), M.703 commanded (way too fast for this altitude)
- above FL250 the commanded MACH speed started to increase slowly (as expected) up to M.075 at FL330 (cruise FL/speed)
- cruise seems to be correct at FL330, M.75, 265IAS, 430GS, 428TAS (side-wind 40 from 080)
- but on descend, again, speed was decreaesing until M.703, then remains constant
- during the descend I tried to pull the SPD knob, dial 270IAS, wait for slow-down and then push it again to re-activate managed speed - it automatically switched to MACH and commanded M.703 (although I was well below FL150!!)
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Re: [A320Family] Managed speed problem

Postby Octal450 » Tue Aug 22, 2017 2:05 pm

Hi
This happens when you do not reach the cruising altitude you set into the MCDU. The system is still in the climb phase. This will be fixed very soon.

157 is the default climb speed if no V2 speed is entered.

The managed speed also needs to be improved, this will happen soon.

Bottom line, if you start your cruise altitude correct, and actually achieve it, then it works correct.

Kind Regards,
Josh
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Re: [A320Family] Managed speed problem

Postby Darkriser » Tue Aug 22, 2017 4:04 pm

I took another test flight because I was only 95% sure that I did enter FL into MCDU :-)

Now I'm 100% sure I did enter CI and cruise FL into MCDU (page INIT, CRZ FL set to FL33).
To be sure I've actually reached the cruising alt, I temporarily climbed to alt 33200 (using STD baro) and then descended back to FL330.
However, the issue on the following descend appeared again.

Is there a way how to find out the mode ITAF is currently in?
I tried to browse the internal variables, but wasn't successful.
Because if you are correct, then my ITAF never achieves cruise phase...for an unknown reason...
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Re: [A320Family] Managed speed problem

Postby Octal450 » Tue Aug 22, 2017 6:05 pm

Hi
ITAF is simply the autoflight, it does not control the phase management, which controls the managed speed.

Do my a favor, will you? Next time it happens, go to /FMGC/status and tell me the value of "phase"

However, if the cruise level is achieved correctly, the PFD (and the IT-AUTOFLIGHT dialog) pitch mode should read "ALT CRZ", otherwise, you will see just "ALT"

Kind Regards,
Josh
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Re: [A320Family] Managed speed problem

Postby Darkriser » Tue Aug 22, 2017 7:02 pm

it0uchpods wrote in Tue Aug 22, 2017 6:05 pm:PFD (and the IT-AUTOFLIGHT dialog) pitch mode should read "ALT CRZ", otherwise, you will see just "ALT"

I'll definitely do another (test) flight and watch (and report) the 'phase' property.
But my PDF definitely did NOT read "ALT CRZ".

Btw. what other internal properties determine value of /FMGC/status ?
I'd like to analyze the root cause of "not being" in CRZ phase.
I would expect some properties like "current alt" and "crz alt"...and if "current alt" >= "crz alt", then /FMGC/status = "CRZ".
thanks a lot...
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Re: [A320Family] Managed speed problem

Postby Octal450 » Tue Aug 22, 2017 9:10 pm

@Darkriser
Not quite. It's not as simple as that ;) In order for ALT CRZ to appear, the cruising level in MCDU must match the FCU altitude, and the IT-AUTOFLIGHT be capture the CRZ altitude Otherwise, ALT is displayed instead.

I'll be putting the bugfix that should fix not transitioning from CLB to DES, even if a descent is triggered.

Kind Regards,
Josh
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Re: [A320Family] Managed speed problem

Postby Darkriser » Tue Aug 22, 2017 10:24 pm

Josh,
call me a dumb egg, pls...
Did you know that FL33 entered in MCDU is waaay much different from FL330??
Of course you did....and now I know too :-)
Sorry for that...

Now all the phases, climb and descend works exactly as expected.
Nevertheless, reaching CRZ ALT really shouldn't be mandatory and deserves a small fix, as mentioned in your previous post.

But...another problem (or feature?) popped out.
To quickly test CRZ ALT, I initially entered FL200 into MCDU, set 20000 on FCU and reached my CRZ ALT ( /FMGC/status/phase == 3)
But then I decided to increase my cruise alt, so I entered FL330 into MCDU, FCU and started to climb again. phase still == 3.
Although I reached FL330 and PDF indicated CRZ ALT, FCU indicated still SPD (not MACH!).
Obviously, this is allowed only in phase 2, not in phase 3.
I manually changed the phase to "2" and voila - FCU switched to MACH :-)

Then I entered FL150 in MCDU, FCU and descended correctly (FCU switched to SPD, as expected!). phase == 4
But then I wanted to climb to FL330 again, so modified MCDU/FCU and started to climb.
However, still in phase 4, FCU indicated SPD (not MACH!) even after reaching FL330.
When I climbed even higher, the speed exceeded M.81 (because FCU still switched to SPD).
When I manually changed phase to "2" again, MACH was immediately commanded on FCU and speed dropped to acceptable M.78 (at FL370).

Looks like either I get it wrong or the 'phase' property is not 'dynamic' enough (doesn't support switching phases back and forth).
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Re: [A320Family] Managed speed problem

Postby Octal450 » Wed Aug 23, 2017 12:27 am

@Darkriser
OK.

You are a dumb egg pls.

Just kidding :lol:

Do not worry. You have brought me 2 bugs to fix:

1: The Descent Phase bug -- should be triggered correctly
2: Smart Phase managemenet -- FMGC should be able to revert to CLB or CRZ, if needed, such as a modified CRZ level.

Kind Regards,
Josh
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Re: [A320Family] Managed speed problem  

Postby Octal450 » Sun Aug 27, 2017 6:19 pm

Our new internal version has the new phase management which fixes this, so I'm marking this as "solved" on our bug tracker. Should be public in a few weeks or less.

Thanks,
Josh
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Re: [A320Family] Managed speed problem

Postby Octal450 » Fri Sep 15, 2017 7:10 pm

Taking more time than expected, I'm going to be rewriting all my flight management stuff I did with the new 2017.3.X Nasal Flightplan system, so I'm keeping the overhauled build private for a while. Also, schoolwork slowes me down a bit.

Kind Regards,
Josh
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