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Manually overriding autothrust

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Manually overriding autothrust

Old 30th Sep 2013, 12:47
  #41 (permalink)  
 
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Originally Posted by vilas
A peculiar thing about this post is a question is asked about an Airbus procedure by a non Airbus pilot and also all the answers and conclusions are drawn by non Airbus people and finally ending up with favourite past time A vs B. I have flown both enjoyed both. I treated them as different concepts. I would not comment on something I don't know.
That's a peculiar thing about most of the internet. People routinely comment on things they haven't the foggiest notion of.
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Old 30th Sep 2013, 14:14
  #42 (permalink)  
 
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To quote from Airbus...

"Except in emergency situations, AP and A/THR must not be overridden manually."

Just curious whether this applies to any other types. I have seen it done for a few moments on Boeings.
Done it on Boeings (B737-777) and MD/DC planes when the automatics didn't wanna do what i wanted it to.

I guess it's all up to design philosophy.
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Old 30th Sep 2013, 14:27
  #43 (permalink)  
 
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Here we are not discussing your company procedures. ATHR disconnect procedure is part of training syllabus while this procedure was not and few pilots obviously have messed up approaches may be by leaving THR LVR in MCT. So now Airbus recommends disconnecting ATHR and use manual thrust instead. If you mess this up you are responsible since you were taught how to. The procedure was useful if you needed quick thrust response.
Whoa there Vilas from Malaysia.

I understand this isn't about my company procedure. I brought up company procedure because I had never heard of that Airbus recommendation before and with it being so recent, I was very surprised it was never covered in our training. I asked two United pilots (both Airbus) what they knew about it and both were unfamiliar as well.

I'm wondering why this is so unfamiliar here, especially with it being such a recent change.

I sent a note off to an instructor in Training and will post when I hear back.
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Old 30th Sep 2013, 14:28
  #44 (permalink)  
 
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That's a peculiar thing about most of the internet. People routinely comment on things they haven't the foggiest notion of.
It would be nice if they at least prefaced their post with something stating their level of knowledge.

"I've never flown an Airbus, but...."
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Old 30th Sep 2013, 14:49
  #45 (permalink)  
 
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Just pointing out:

Originally Posted by JammedStab View Post
My mistake, it was referring to a runaway situation or hardover.

I believe they mean in this situation to disconnect. Only override if disconnection is not possible and an emergency situation has been created due to the malfunction.

The original poster noted that he had misread the context back in post #14, and yet here we are at post #45 with most of them being random sniping about Airbus and automation dependency...
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Old 30th Sep 2013, 15:04
  #46 (permalink)  
 
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loss of face.
Been there.
Seen B737 crews run of the end of a long runway where we landed a B777 minutes before.

It's the asian 185 kts flaps5 landings gone wrong.

That was a replay to Centaurus post 19.

Edit to add: we landed with lots of runway to spare.

Last edited by Capt. Inop; 30th Sep 2013 at 15:24.
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Old 30th Sep 2013, 15:18
  #47 (permalink)  
 
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Altcrznav
I think you should take it easy. If your airline hasn't provided this information to you for whatever reason then you are not at fault. This procedure was in place for some years but it was circulated only through Flight Crew Bulletin. It was only removed in 2011. If your instructors were provided with the same documents then it is likely that they also don't know about it. Having said that just because your Airline didn't use it does not make it crappy. It was removed not because it was ineffective but due to improper use by some pilots.

Last edited by vilas; 30th Sep 2013 at 15:23.
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Old 30th Sep 2013, 15:46
  #48 (permalink)  
 
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The biggest problem with phase advance was people carrying it out below 100' RA. They click forward, click back to climb, and suddenly full climb thrust is commanded as the autothrust has turned itself off.
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Old 30th Sep 2013, 21:37
  #49 (permalink)  
 
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I have clicked off the auto systems any time they aren't doing what they should. Two clicks and you are fine. I would not want to fly with any pilot that couldn't do that and land safely. Airbus has a different philosophy but that is also why I never flew an Airbus. You are the pilot so don't let automation control you, you control automation.
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Old 30th Sep 2013, 21:58
  #50 (permalink)  
 
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Originally Posted by bubbers44 View Post
I have clicked off the auto systems any time they aren't doing what they should. Two clicks and you are fine.
Bubs - JammedStab has been trying to tell you lot since post #14 that he misunderstood the context. I replied to your post on the other thread, but the document referred to is basically saying nothing more than 'disconnect the automation via the button before moving the controls'.

The document also explicitly instructs pilots to handfly - with raw data if necessary - if the automation behaviour is doubtful.

http://www.airbus.com/fileadmin/medi..._SOP_SEQ02.pdf

(Bottom of page 7)
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Old 30th Sep 2013, 22:00
  #51 (permalink)  
 
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The biggest problem with phase advance was people carrying it out below 100' RA. They click forward, click back to climb, and suddenly full climb thrust is commanded as the autothrust has turned itself off.
There it is right there. Why would you want to bounce in and out of different levels of automation on final? You don't have time to figure out what's going on if you screw it up or don't react fast enough.

That's why its a crap procedure. You cannot possibly be stabilized when your degrading automation and then upgrading it again.
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Old 30th Sep 2013, 22:44
  #52 (permalink)  
 
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Gordon Bennett - let's just have a look at what the thing actually says, shall we?

VII.3 Take actions if things do not go as expected

This is the Golden Rule number 4. If doubt exists regarding the aircraft flight path or speed control, the flight crew should not try to reprogram the automated systems.

The flight crew should use Selected Guidance or hand flying together with the use of navaids raw data, until time and conditions permit a reprogramming of the AP/FD or FMS.

If the aircraft does not follow the intended flight path, check the AP and A/THR engagement status.

If engaged, disconnect the AP and/or A/THR using the associated instinctive disconnect push button(s), to revert to hand flying (with FD guidance or with reference to raw data) and/or to manual thrust control.
In hand flying, the PF must follow FD commands; otherwise the flight crew must remove the FD from the PFD.

AP and A/THR must not be overridden manually.

If AP or A/THR operation needs to be overridden (i.e., following a runaway or hardover), immediately disconnect the affected system by pressing the associated instinctive disconnect push button.
So, now we can see it in context it becomes clear that:
  • The section refers only to a scenario in which behaviour is unexpected
  • The document explicitly says that pilot should handfly using raw data if necessary (and in an official Airbus document no less - who'dathunkit? )
  • There is no restriction on manual override without disconnect if the automation is behaving as expected
  • The statement from the original post simply means that disconnect must be performed before taking manual control - presumably to ensure that a malfunctioning system is definitely no longer part of the problem

Last edited by DozyWannabe; 30th Sep 2013 at 22:47.
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Old 1st Oct 2013, 01:06
  #53 (permalink)  
 
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In general do not override / overpower automatic systems

In general do not override / overpower automatic systems when there is an option to disengage via another mechanism.
Depending on the systems design / certification, overriding / overpowering can result in in some serious even hazardous situations. Older auto-throttles which interface with hydro mechanical fuel controls via 'fuel trim' systems may result in full travel trim and inadvertent over speeding /over temp or sub idle / shutdown. Slip clutches may provide some protection but in doing so can be damaged which in subsequent operation fail to work correctly.

Most modern autopilots guard against overpowering with force/displacement cut outs which minimise out of trim forces. Older autopilots may not, overriding these might result in a large opposing trim movement such that the resulting stick force cannot be managed – several upset accident reports.
Modern auto flight systems may have related characteristics, but without the force-feedback due to auto-trim follow up or similar. Remember that if you override the controls it may affect trim, trim is a control, and is very powerful.

You would not expect the PNF to ‘help’ the PF by overriding the control (except the trainers); the fate is coarse words or a ‘clip round the ears’. An autopilot/trim is much stronger and less forgiving of such assistance; you don’t train the auto system by overriding it, it’s more likely to train you not to do it again.

If you are going to put your hands on the thrust lever/controls to override, then why not press the adjacent disengage switch – they were designed with the human in mind.
But not all designs cope with the mind of the human.
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Old 1st Oct 2013, 02:42
  #54 (permalink)  
 
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Altcrznav
It is obvious you are not taking it very well that you were not aware of this procedure. You are trying to clutch at the slightest evidence no matter how ridiculous that the procedure was crap. Kindly examine the first line of the procedure.
"During the approach, with the A/THR active, Airbus recommended to set the thrust levers above the CL detent (but below the MCT detent), in exceptional circumstances, if the speed significantly dropped below VAPP."
When speed significantly dropps below 100', you simply go around. Even in your airline. Any pilot who tried to do anything else deserves your favourite word crap.
However this procedure did not come out of thin air. DSC-22-30-90P5/14 is quoted below:
The thrust levers provide the flight crew with an immediate increase of thrust when both thrust levers are pushed above the CL detent (two engines) or the active thrust lever above the MCT detent (one engine operative).
Last but not least United Airlines manual revision shows this FCB.
Thank you.
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Old 1st Oct 2013, 02:59
  #55 (permalink)  
 
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Originally Posted by Altcrznav
I brought up company procedure because I had never heard of that Airbus recommendation before and with it being so recent, I was very surprised it was never covered in our training.
It was NOT recent. The oldest reference I can find is from 2004. What is recent is that Airbus no longer recommends the use of such procedure.


Originally Posted by tom775257
The biggest problem with phase advance was people carrying it out below 100' RA. They click forward, click back to climb, and suddenly full climb thrust is commanded as the autothrust has turned itself off.
Correct. Airbus have engineered a system and procedure that behave very differently depending of the altitude ... Confusion is probably one of the "drawbacks".
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Old 1st Oct 2013, 03:08
  #56 (permalink)  
 
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Originally Posted by Dozy
random sniping about Airbus
Quite justified in this scenario. A short override of the Autothrottle should not result in

They click forward, click back to climb, and suddenly full climb thrust is commanded as the autothrust has turned itself off
In my Boeing, if you fall in a hole and need to help the ATS, you simply push the throttles up as required (or close the throttles if that's what's needed) then let go; the ATS will then move the throttles back to where it thinks they should be. There's none of this nonsense of leaving them out of a detent for too long will set off climb power. Computer game designed by boffins and out-of-touch-with-reality test pilots.
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Old 1st Oct 2013, 06:45
  #57 (permalink)  
 
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Originally Posted by vilas View Post
I would not comment on something I don't know.
Odd, I seem to recall you bloviating quite extensively on proper procedures for operating off of ice runways, something you have never done yourself.
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Old 1st Oct 2013, 12:26
  #58 (permalink)  
 
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A squared
The question had nothing to do with ice, the answer I gave had nothing to do with ice it was you who sanctimoniously dragged the discussion to ice as if ice age has arrived and told us how you keep warm in an igloo. Thank you but I am not interested and since you won't have anything on the subject at hand I take your leave.

Last edited by vilas; 1st Oct 2013 at 12:27.
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Old 1st Oct 2013, 13:19
  #59 (permalink)  
 
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@Capn Bloggs:

Did you not read the extract? The restriction applies *only when the automation is not behaving as expected*.

When A/THR is engaged, the thrust levers behave differently to your Boeing, and the idea is that they remain in their detents for the duration of the flight. When A/THR is disengaged (or automatically disengages) then the thrust remains at the last setting prior to disconnect.

The only way you'll end up in the situation you're describing is if you move the thrust levers to the climb detent after disconnecting. Or if they were in the climb detent at disconnect, you'd have to "jiggle" the levers and leave them in the climb detent/region - not recommended procedure in any aircraft, including "your" Boeing!
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Old 1st Oct 2013, 21:08
  #60 (permalink)  
 
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CONF iture wrote:

It was NOT recent. The oldest reference I can find is from 2004. What is recent is that Airbus no longer recommends the use of such procedure.
I was going off of vilas' post. He shows a 2011 date for the bulletin.
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