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Managed Speed at Cruise


Sabretooth78

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I just encountered an issue with managed speed apparently changing mid-cruise on the A321 IAE, v.1.2.1.3.

 

I had stepped away from the PC to make dinner, and popped back into the room to check to make sure I wasn't flying into a thunderstorm - I wasn't, but I noticed that the a/c was pitched up about 10 degrees and the speed tape was just about down into the yellow hatch.  Pushing the thrust levers into TOGA didn't seem to be fixing the situation so I dialed the FCU altitude window from FL340 to FL310.  Again, nothing doing, so I pushed the stick forward and nosed over, this time with the speed tape in the red (but somehow avoided a stall), recovering at around FL320 where I was then able to eventually climb back up to FL340.  However, at some point during this re-climb I noticed the speed target moved from 278 down to 128 (!) so I set selected speed to M0.80 and have more or less been able to continue merrily along my way.  That said, if I try to re-enter managed speed, the target drops to 130 and the engines quickly idle and re-engaging selected speed always starts back in KTS and not MACH.  This is my first encounter with an issue of this magnitude with the Pro buses, in some 60+ hours of VA flying (granted, mostly on the A320 IAE).  Are there any other reports of this behavior?

 

Some pictures:  Note the speed targets, however everything on the CDU appears to be correct!?

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Flight plan is KFLL N0464F340 BEECH5 BAHMA DCT ZOLLA A301 URSUS UL780 TASNO UL780 GAXER UL780 DALUD STAR5 SEGU.  I'm not exactly sure when the behavior started, however, I do know for a fact it didn't occur at a waypoint (somewhere past GAXER), and the issue persists after passing the following waypoints (DAGUD and LIVUD thus far).  Perhaps it's just some side effect of the greater problem with vertical profiles?  Somehow related to flying above the OPT FL?  (The speed target did change somewhere during the recovery, during which I had dropped below OPT.)

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This has been reported before and is being looked into.  For the time being when you step away just select the speed until you return.  As a temporary fix when i see this happen i have copied the secondary flight plan and then activated the secondary flight plan and the issue goes away and my speed returns.  

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Mee too,

my cruise (and climb speed) calculated by mcdu was 204 KIAS!  (I selected 290 at cruise fl 210) and I've used 1.2.1.4. a320 cfm and a "turnaround state" situation

Ciao

Andrea

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Hi,

but starting by a "cold and dark situation" I've no problem ..i.e. with a cost index= 7 I got a cruise speed of 294 kias (I can't remember the mach n.)

Best Regards

Andrea Buono

 

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Same here.  Came back from another room to find my Airbus A320 plummeting towards the sea in a high altitude stall.

Tried resetting A/P F/D, CRZ speed, CI - no joy.  The only way to keep flying was in selected speed mode.

 

 

 

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20 minutes ago, Mathijs Kok said:

The most logical cause of that issue would be an incomplete set of data in the MCDU. 

 

Like I posted in another thread, I've seen this happen when changing the arrival STAR/RWY while in flight.

 

Could it be a desync with the #1 and #2 MCDU? On a recent flight I had a case of AP1 not engaging with MCDU INIT A/B both done correctly. AP2 engaged correctly and flew the route as programmed. I've also had a flight where I couldn't engage either AP even with INIT A and B done correctly.

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And it happened again, flying KSAN to KJFK in JBU A321 IAE. After reaching cruise level of FL330 and putting in a direct, shortly after the engines went to idle with managed speed of 126 knots. Airbus is updated to today's experimental patch.

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On 11/19/2018 at 12:00 PM, Mathijs Kok said:

Can you check this using the Step-by-Step flight? Only then we know we are all dealing with the same variables. 

 

As said we think the issue is in preflight.

 

Nope. I do enough of IT "stuff" during work hours, I'm not going through a +100 page document to debug your plane. Give me something to work with and I might be more willing to go through all the trouble.

 

POST EDITED BY STAFF TO REMOVE FOUL LANGAUGE, SECOND TIME FOR THIS USER, WILL NOT BE A THIRD TIME.

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  • Aerosoft

Okay sir, if you are unwilling to read manuals for complex aircraft add-ons there is not a lot we can do.

I am sorry you feel our manuals are the same as the stuff you have to deal with in your work. Can I suggest a change of employment?

 

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