Dual RA Fault A320
Joined: Apr 2003
Aviation Qualifications: ATPL
Posts: 3,652
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From: Europe
I’m not sure I understand the last two posts, could you please elaborate? Why would direct law activate differently immediately (i.s.o.when lowering the gear) when Final App is engaged?
Joined: Oct 2019
Posts: 234
Likes: 12
From: SW1A 2AA
When I did this in the sim, the aircraft cannot follow the G/S with both RA's failed. So it needs to be flown in managed approach or V/S or FPA. It't the only time you can go from normal law straight to direct law, to my knowledge. Happens when the gear is lowered. Been a few years since I flew the Airbus though....
Joined: Mar 2012
Posts: 2,605
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From: Having a margarita on the beach
The question raised by vilas is quite interesting; I believe that the vast majority of us have seen the Dual RA fault only in the sim (at least I have despite being on the A320 since 95) and in addition with the usual scenario: dispatch with 1 RA in MEL then loose the second one somewhere in flight directly or as a result of an electrical failure affecting it. To be honest despite thousand and thousand of sim hours I believe I haven’t worked on a scenario where the second RA is lot after LG down; at least I can’t recall if. Logically speaking the answer should be Yes, I.e. loss of second RA triggers direct Law hence AP disconnect. Will definitely try it out when I get a chance.
Joined: Dec 2020
Posts: 71
Likes: 110
From: Scandinavia-home of the midnight sun.
It is not clearly described in the Airbus documentation, but there are instances where AP is available in alternate law, and then the bus will NOT go into direct law upon landing gear extension, but when you disconnect the AP.
This is confusing to lots of pilots, as the AP in most cases disconnect when the aircraft degrades to altn. law (with the resulting direct law upon L/G extension).
Summary: IF AP is available and engaged in altn.law, then degradation to direct law occurs with AP disconnect i.s.o. L/G down.
This is confirmed in the sim (A320 neo) and confirmed by Airbus (upon query from our fleet office).
Rgds,
This is confusing to lots of pilots, as the AP in most cases disconnect when the aircraft degrades to altn. law (with the resulting direct law upon L/G extension).
Summary: IF AP is available and engaged in altn.law, then degradation to direct law occurs with AP disconnect i.s.o. L/G down.
This is confirmed in the sim (A320 neo) and confirmed by Airbus (upon query from our fleet office).
Rgds,
Joined: Aug 2007
Posts: 98
Likes: 2
From: Middle East
When you lose the 2nd RA, the F/Ctl will switch to Direct and AP trips as long as the LG is down....
the plane is made that way because the Flare mode (100 ft on A330) is no longer available in dual RA fault and Airbus has to select a point during approach where the autotrim must be stopped to facilitate the landing and make it natural and easy and that point was L/G down.....
the Direct Law in such a failure (dual RA fault) is not like any other Direct law. It is close to being Normal Law w/o autotrim....
sorry if my wording is not understandable as English is not my native language....
the plane is made that way because the Flare mode (100 ft on A330) is no longer available in dual RA fault and Airbus has to select a point during approach where the autotrim must be stopped to facilitate the landing and make it natural and easy and that point was L/G down.....
the Direct Law in such a failure (dual RA fault) is not like any other Direct law. It is close to being Normal Law w/o autotrim....
sorry if my wording is not understandable as English is not my native language....
