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Speedbrake efficiency


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To be honest this looks pretty normal to me. 240kt and 1400fpm descend looks ok in my eyes, but I'll ask one of our testpilots to confirm it.

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To be honest this looks pretty normal to me. 240kt and 1400fpm descend looks ok in my eyes, but I'll ask one of our testpilots to confirm it.

I think you don't understand the problem:

The problem is not to have 240ias at 1400fpm, the problem is, that the speedbrake is not reducing it.

This was working fine with 1.21d.

Please take a deeper look to this situation above:

I'm on a very final approach state. at this state, normally the airbus must reducing speed to "clean speed" but it stuck on 240IAS also with headwind AND speedbrakes fully extanded.

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  • Deputy Sheriffs

i dont understand why when you install hotfix there something new that its buggy.

Hello Eduard,

this post might explain that (your question, not the speed brake problem).

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(...)

The problem is not to have 240ias at 1400fpm, the problem is, that the speedbrake is not reducing it.

(...)

A GS of 230 kts requires about 1.200 fpm in order to stay on the glideslope. There would be a tendency to accelerate in a clean configuration, I reckon. When speedbrakes are extended in that situation, the added drag goes into fighting the acceleration first. Only "remaining" drag could actually slow the aircraft down. I am not sure about the amount of "surplus drag" in that situation. Specifically in the A320, A/P engagement also reduces speedbrake extension and efficiency.

My question here is, what had happened before getting established on the ILS? 240 kts airspeed is way above standard speeds for intercepting either the localizer or the glideslope. Any difficulties to slow down before LOC interception, or was the high speed on the ILS caused by something else?

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I think you don't understand the problem:

The problem is not to have 240ias at 1400fpm, the problem is, that the speedbrake is not reducing it.

This was working fine with 1.21d.

Please take a deeper look to this situation above:

I'm on a very final approach state. at this state, normally the airbus must reducing speed to "clean speed" but it stuck on 240IAS also with headwind AND speedbrakes fully extanded.

Don't worry, I did understand the problem.

Your problem is just that you're trying to descend rapidly and slow down at the same time, which is not a very good idea.

If you fly 240kt on a Glideslope you can basically immediatly go around. You're just to fast. Speedbrakes are no parachute, they can slow you down, but not very much. You may be over estimating their effectiveness.

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When you pass over DECEL, the aircraft isnt reducing the SPEED. I even used the speedbreak but no go. I tested A320 IAE. Test it and you will see.

PS: I just tried to go around but the aircraft went deep into the ground lol

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Have you activated Approach phase?

Also non standard gear down will create you the needed drag but as say before 240 kts at that stage is already an unstabilized app and you should go around

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Don't worry, I did understand the problem.

Your problem is just that you're trying to descend rapidly and slow down at the same time, which is not a very good idea.

If you fly 240kt on a Glideslope you can basically immediatly go around. You're just to fast. Speedbrakes are no parachute, they can slow you down, but not very much. You may be over estimating their effectiveness.

Emi -

My very humble opinion on this is that the perceived loss of speedbrake effectiveness is a SYMPTOM here, and that the root of this issue is the fact that the autothrust is keeping the speed up too long in Managed Speed/Approach Mode for the A320 IAE model. I just did a flight in sort of a standard testing scenario and the system would not let the speed decay down to -S after I selected Flaps 1 (for example)...when it decreased to 200KTS it actually powered up to maintain that speed (which is coincidentally marked as the max speed for (F)laps). The indication on the PFD fluctuated between IDLE and SPEED at that time. I had to pull the speed knob out and deploy speedbrakes, after which the autothrust started to obey my selected speed command.

In other words, I believe that the only reason that Martin is blasting down the G/S at 240kts is because the autothrust system in Approach Mode refused to let him slow down in time.

Again, per my earlier flight today the CFM seems to work fine on my computer (FSX with Acceleration).

We're talking about the same thing over in this thread: http://forum.aerosoft.com/index.php?/topic/94598-speed-not-being-controlled-correctly-on-approach/

Thanks -

Matt

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