Problem A320 FBW stable version to descend

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1

Today I have problem flying A320 FBW, stable version, to dfescend: with AP, It was very difficult to descend, I have to do it manually without AP.

2

What altitude were you at when this happened?
Was there an altitude constraint in the FMC at the time?
Did you use managed, or open descent?
Did you try vertical speed?

3
  • 39000 feet
  • No constrait in FMC at that time
  • I use both
  • I also use vertical speed
4

Today the same: I can not descend.

Sin tĂ­tulo 4
Sin tĂ­tulo 41920Ă—804 103 KB

5

Not sure if this helps but you sure the AP is working that close to overspeed? Heard someone in the FBW Discord server saying when in the red region the AP disengages

Also, why are you flying the speed manually and not letting the auto throttle control it ? Have you tried setting your thrust levers to the CLB detent to allow it to manage it?

6

Wow that’s pretty fast.
At that speed, it probably can’t descend.

In any aircraft:
Amount of thrust = climb/descent
Degree of pitch = speed

You have way to much lift at that speed to descend.
Normal cruise is approximately .78M
Reduce throttles to maintain that speed until mach change to indicated airspeed (around FL280).
After that you should be about 290 knots, you should have no problems with descending.

Also, in order for the automation to work properly, the throttles, as mentioned above, must be in the “Climb” position.

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7

Yeah hes right you cant decend with the AP at 340 knts what are you a manic… LOL

that being said before you start a descent or even a climb, lower your airspeed to 280-300 knts then tell it to descend or climb.

8

After I recalibrate, I could put CL. And also in Cost Index, I don´t put nothing, before I put 11. The speed was now 290, and I have no problem to descend.

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9

Great news.
I’m not 100% sure, but I don’t believe the cost index does anything just yet.

10

The problem isn’t the Cost Index (CI). It’s your throttle position. From your screenshot your throttle is not in CL position, so the Autothrust is not managing the speed. That’s why you couldn’t descend.

It’s good that you have recalibrated the throttle and able to set the throttle to CL. That’s why the Autothrust work and you’re able to descend.

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