A320/A319 speed brakes
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Joined: Jul 2006
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From: 'tween posts
A320/A319 speed brakes
On the 320 with autopilot on speed brakes are limited to half detent
whereas on 319 they can be extended all the way(full). My guess is that with the lesser weight, wing loading is reduced and as a result the autopilot is able to handle it ????.....anyones knows the correct reason.
whereas on 319 they can be extended all the way(full). My guess is that with the lesser weight, wing loading is reduced and as a result the autopilot is able to handle it ????.....anyones knows the correct reason.
Joined: Mar 2006
Posts: 17
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From: Europe
I think this has to do with improvements of the autopilot and how new the models are. Think there were some early versions of the A319 also where you could use only half speedbrake with the AP enganged, but they improved that in later versions (and I think that applies to newer versions of the A320/321 as well). Correct me anybody if I'm wrong.
Last edited by Coanda F. Eckt; 5th August 2006 at 13:06.
Joined: Jan 1999
Posts: 187
Likes: 1
From: hongkong
Thought it was more to do with Vls increasing with spoiler movement in the emergency desent case. Originally I believe that the a/c came with full spolier deployment with AP in, but was modified in the light of experience....could be wrong though!
Joined: Aug 2002
Posts: 1,658
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From: Up north
Well, at high alt Vls will be to high for full speed brake...Further, the AP is not that good at dealing with full speed brake at high alt. If you are high on profile and descending managed, then the managed max speed/mach will be quite close to barb pole and with the flight management/AP trying to achieve "on profile" you will accelarate to, and often beyond, max managed speed/mach. When speed/mach reaches max managed, the AP is pitching up to reduce speed, however, it will try to maintain 1 G...thus resulting in a over-speed situation crew throwing away coffe/newspapers/hosties to de-select AP and bring the speed back.
A bit off the topic perhaps...but may be interesting for non-bus drivers....
/CP
A bit off the topic perhaps...but may be interesting for non-bus drivers....
/CP
Joined: Apr 2006
Posts: 2
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From: Germany
Reason that u can use full spoilers with AP on in 19/21 is, that 319/21 max spoiler deflection is the same as 320´s half spoiler deflection....
So descend gradient is best on a320 AP off and full speed breaks... IT WORKS!!
Cheers
So descend gradient is best on a320 AP off and full speed breaks... IT WORKS!!
Cheers
Joined: Jan 2006
Posts: 454
Likes: 3
From: Georgia, USA
I think you will find it is because of the distance between the wing trailing edge and the horiziontal stabilizer. Because of the shorther distance on the 318/319, full spoilers disrupts the airflow over the horiziontal, causing excessive pitch up.
