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Airbus 320 suddenly start to descend through its decided altitude


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Hi!

 

I have a problem now with the Airbus 320 (not FBW Airbus). When ATC clears me to a lower altitude the Airbus sinks through this altitude. This happens when closing to approach part. ATC clears me from 11000 feet to 7000 feet, and the Airbus go on sinking under this altitude. I am in manged mode, auto throttle, and on auto pilot. To save the situation I must give full throttle, but the slow reaction before the airbus starts climbing again give a close call to ground. Speed is slowed to 210 knots on ATC clearing, but I have to speed up to be able to climb.

Once I manually (hand flying with autothrottle de-engaged) are in right altitude I can go back to managed mode and with autopilot and auto throttle engaged, and the Airbus are flying the ILS approach without any other incidents.

This strange behavior happens at any given aiport I arrive - at least those 4-5 times lately it has happened after last sim-update.

 

Others have experienced the same behavior - or knows what could course this?

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From reading your post my instant thought is you may not have the throttle set correctly as this will sometimes cause conflicts. Anyways to give you some idea of what I do and I fly the 320 alot. First before engaging the AP on climb out make sure you retard the throttle into the CL position, it should feel like a click as it hits the right spot. Then engage the AP with auto throttle engaged and heading set to managed BUT use Select to control the altitude, basically dial in the alt press the knob in to select, stay out of managed mode for altitudes trust me your life will be a lot easier. Also upon decent turn off auto throttle and manage your speed by yourself by dialing in the appropriate speed and use the altitude mode in select to dial down your altitude as you descend. Also a tip is to have minimums turned on with your display at 10 or 20 range. Minimums can be turned on by pushing the CRS or CSM i forget but its by the display knobs on the dash directly in front of you. The minimums are important because sometimes ATC isnt exact and if you are flyin an ILS approach it tells you what altitude you need to be at as you fly the approach. So bottom line is in my experience, ONLY use managed for heading and throttle Use selected for altitude and life will be easier all around.
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In the flight mentioned I had turned off Auto throttle and used selected mode to slow down from 250 knots to 210 knots when incident happend. But yes - I am sure of using CL-mode throttle after take-off phase.

Your tip about selected-mode altitude seem to fix issue. I just had a flight now with no incidents,

But the minimums knob I am not able to locate - are you talking about the FBW-Airbus?

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No I only use the Asobo, crap I am at work and cant access the panel but to the left of the airspeed control on the top of the dash are some dials and switches. One is the range changer for your FMC/or route display to the left of that is a button CRS or CSM but if you hover your mouse over it it should say "restraints" turn that on, it shows your minimums for each waypoint on your flight path on ILS. You should be able to change your range from 20nm to 160nm and it might go as low as 10.. My old age is hampering my memory, also turn the terrain on if you dont have it already and your display showing your pink line will also show terrain to help with the flyi9ng in the mountains. That button is on the main dash to the right of the route display.
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I still cannot find this knob CRS/CFM?

But yesterday a similar incident happened on approach from 11000feet to 7000feet on advise from ATC. And I was in selected mode altitude on descent. I had to turn off Auto pilot and auto throttle and had to handfly all the way to touch down - this time the Airbus was not able to regain normal operation so I could use Autopilot and ILS in automode like incidents similar occasions earlier.

This behavior seem very strange, and I really dont understand what causes it - sometimes normal operation, and sometimes this odd behavior?

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