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Manually overriding autothrust

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Manually overriding autothrust

Old 29th Sep 2013, 14:31
  #21 (permalink)  
 
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Really?...... The last few posts make me shiver, for so many basic reasons it's not worth talking about

I guess that Airbus' just aren't tactile machinery ....that's all there is to it!

Boeings are very much so, tho..... even the Tripple is tactile for a FBW

Altcrznav..........you do understand now, Yeah?

Last edited by Buttscratcher; 29th Sep 2013 at 14:51.
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Old 29th Sep 2013, 15:49
  #22 (permalink)  
 
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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.
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Old 29th Sep 2013, 16:28
  #23 (permalink)  
 
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A few people here are getting confused between over -ride and disconnect.
Explain the difference in an Airbus.
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Old 29th Sep 2013, 16:37
  #24 (permalink)  
 
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Wizofoz

I think the confusion is between "Over-ride" and "Disconnect". I don't think AB is saying don't disconnect or downgrade automation if it isn't delivering what is required- but don't OVER-RIDE that is, make manual inputs while the automation is still connected, unless it's a serious, time critical problem.

In a Boeing, the same would be true of the A/P, though there's no problem "Helping" the A/T a bit if it is slow correcting the speed.
Making manual inputs while automation is still connected is not unusual nor abnormal. We have 4 levels of automation and, for example, changing heading to avoid a cell would simply be a change to the level of automation. Nothing is over-ridden and I don't ever remember seeing that referenced.

You don't over-ride anything but merely change levels. Level on is all automation off (occasionally final approach) and level 4 is fully automated (CRZ).
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Old 29th Sep 2013, 17:11
  #25 (permalink)  
 
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Alt,

Changing from, say, LNAV to HDG SEL to avoid a cell is neither disconnecting nor over-riding automation, it is simply changing mode, and as such is not a manual intervention.

Manual flight implies direct control input- i.e via the yolk in a Boeing, and that would NOT be a normal input while the A/P was still connected.

If a sudden, time critical intervention was required, disconnect and manual flight would be appropriate.

Last edited by Wizofoz; 29th Sep 2013 at 17:13.
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Old 29th Sep 2013, 17:23
  #26 (permalink)  
 
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I understand that.

But this thread was started as a reference for Airbus which doesn't have an over-ride.

Why are we talking Boeing stuff?
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Old 29th Sep 2013, 17:26
  #27 (permalink)  
 
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Fair enough, I have little knowledge about Airbi- But if you CAN'T over-ride an Airbus A/P-A/T, why does the Airbus manual contain a statement to not DO so except in an emergency?
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Old 29th Sep 2013, 17:33
  #28 (permalink)  
 
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Golden Rules.... AIRBUS

From Airbus FCTM........

I THINK NO.6 answers the question.....

Could be applied to any modern aircraft really.

1.The aircraft can be flown like any other aircraft 2.Fly, navigate, communicate - in that order 3.One head up at all times 4.Cross check the accuracy of the FMS 5.Know your FMA at all times 6.When things don't go as expected - take over 7.Use the proper level of automation for the task 8.Practice task sharing and back-up each other
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Old 29th Sep 2013, 17:44
  #29 (permalink)  
 
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That's not over-riding the Airbus automation, its turning it off or changing to a different level of automation.

Again, you DO NOT over-ride Airbus automation. You downgrade it to a different level.
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Old 29th Sep 2013, 18:09
  #30 (permalink)  
 
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There used to be an airbus procedure that sugested momentarily pushing the thust levers above the climb detent if the autothrust was slow to correct an underspeed in approach. It is a technique that I have used (only rearly I may add) and it worked ok.

I can no longer find a reference for the procedure, has it been taken out?
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Old 29th Sep 2013, 20:45
  #31 (permalink)  
 
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I hope so because it'll get you into trouble.

Fifteen years on the Bus and I've never heard of that recommendation.
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Old 29th Sep 2013, 21:33
  #32 (permalink)  
 
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Just curious whether this applies to any other types.
It applies to any classic controls, autopilot equipped type (e.g. A300 and 310). Don't fight the autopilot. Just don't.

For those who want to know more, IIRC back in late 1990ies Richard L Collins reported about experiment in which GA pilots were put in Malibu simulator and given "soft" AP failure with descent initiated in altitude hold. Quite a lot of them thought they can just pull a bit back on the yoke while keeping the AP engaged to return the aeroplane back to altitude and keep it there. Many of them were eventually simulated killed through dive into ground coming from extreme nose down trim introduced by AP. Interestingly, Nagoya A300 catastrophe was quite similar; pilot was fighting the pitchup with down elevator and still active AP fought it by trimming the stab up.

Explain the difference in an Airbus.
N/A for FBW Airbi. Attempt to override (introduce manual input through stick with AP engaged) will invariably lead to AP discon. Quote that started the thread is from general brand A operations note, dealing with their entire catalogue.

Making manual inputs while automation is still connected is not unusual nor abnormal.
Provided hand is coupled to FCU, not to stick. That needs not be everyone's (or even majority's) definition of manual.
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Old 29th Sep 2013, 23:01
  #33 (permalink)  
 
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Provided hand is coupled to FCU, not to stick. That needs not be everyone's (or even majority's) definition of manual.
I don't understand your comment. Its superfluous.

If your hand is "coupled" to the stick and your making inputs, you're going to disconnect the autopilot.

You cannot make stick inputs with the AP on in the Airbus - period.
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Old 30th Sep 2013, 00:34
  #34 (permalink)  
 
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Originally Posted by Altcrznav
Fifteen years on the Bus and I've never heard of that recommendation.
Then you probably never got the chance to read the Flight Crew Bulletins, part of the FCOM.

Originally Posted by Elephant and Castle
I can no longer find a reference for the procedure, has it been taken out?
I think you're wright !
It appears such procedure is not mentioned anymore ... Airbus did not publicize much why they now think it is better not to mention it any longer ... ?
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Old 30th Sep 2013, 04:03
  #35 (permalink)  
 
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WIZOFOZ, Elephant and Castel, Altcrznav
Further to my Post#18
1. Override in A320 means disconnecting AP by forcing the side stick. Since it unusual way may be done in emergency.
2. Elephant and castle is right there was a procedure to push thrust levers slightly beyond CLB to get better response.
3. Atcrznav I am surprised you did not know it for 15 years. Anyway you need not know it now. Below is from FCOM Flight Crew bulletins.

Ident.:FCB-FCB24-00013125.0001001 / 31 MAR 11

Applicable to: ALL

REASON FOR ISSUE

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. However this procedure is not trained and proved to have more drawbacks than advantages. Therefore, Airbus no longer recommends to use this procedure. The procedure is deleted from the operational documentation.
If the A/THR performance is not satisfactory, the flight crew should take over,and control the thrust manually.

Last edited by vilas; 30th Sep 2013 at 04:06.
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Old 30th Sep 2013, 06:15
  #36 (permalink)  
 
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1. Override in A320 means disconnecting AP by forcing the side stick. Since it unusual way may be done in emergency.
That's another odd (rather stupid) procedure. Why would you risk jamming the sidestick with enough force to overcome the lock and risk putting the aircraft in an inadvertent attitude when you have an ICO right there?

Unusual is a mild way to describe that technique to say the least.

I don't have an FCOM in from of my as my company has its own manuals for training, but does Airbus use the term "override" and "autopilot" together or does it use "disconnect"?


3. Atcrznav I am surprised you did not know it for 15 years. Anyway you need not know it now. Below is from FCOM Flight Crew bulletins.

Ident.:FCB-FCB24-00013125.0001001 / 31 MAR 11

Applicable to: ALL

REASON FOR ISSUE

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. However this procedure is not trained and proved to have more drawbacks than advantages. Therefore, Airbus no longer recommends to use this procedure. The procedure is deleted from the operational documentation.
If the A/THR performance is not satisfactory, the flight crew should take over,and control the thrust manually.
Its quite obvious from the bulletin that it was a crappy procedure and the key there is the it was not trained. My company never adopted it and it was never brought up. I've asked other Airbus drivers about this on our pilot board and none have ever heard of this either - some with many more years than I in the Bus.
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Old 30th Sep 2013, 06:20
  #37 (permalink)  
 
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You CAN override the autopilot on the Airbus, (but you shouldn't).

If you move the rudder pedals or the side stick with the autopilot engaged, the autopilot will disconnect.

The side stick is locked in neutral when the autopilot is on, but you can move it with enough force, at which point, as I say, the autopilot will disconnect. I suppose this allows an emergency reaction from a pilot given something really sudden and bad, such as a potential collision?

We used to be allowed to "Phase advance" the thrust levers by pushing them just out of the CLB gate and straight back into the gate again to increase revs on approach if the autothrust was being lazy, but this now has been outlawed. (I personally thought it was a very useful procedure, but a lot of pilots obviously misunderstood it and left the levers forward of the CLB gate for too long (i.e. more than a second, and ended up overspeeding).

All other actions, as others have said, are mode changes.

(sorry Alt - think we crossed there)

Last edited by Uplinker; 30th Sep 2013 at 06:24.
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Old 30th Sep 2013, 06:43
  #38 (permalink)  
 
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For me it was not needed often but very ocassionally it was quite useful. It was not trained? Not sure what is there to train. If the autothrust is not reacting to a slow speed in approach you move the levers just forward of the climb gate and back into the gate. That wakes the autothrust up so to speak. Hardly rocket science. Crappy procedure? How do you know, presumably you have never tried it.

AB now recomends disconnecting the autothrust all together if it is not performing. Fine, but this also involves overiding the automation momentarily to match the thrust lever position to the current thrust before pressing the disconnect button. Otherwise you end up with a sudden rush of climb thrust until you retard the levers.
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Old 30th Sep 2013, 07:48
  #39 (permalink)  
 
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Altcrznav
Jammed stab's quote I have not seen yet but was explaining the implications in Airbus FBW.
As you are aware you cannot override/overpower AP in Airbus it will disengage. There are three ways you can disconnect the AP only one is recommended i.e. ID button, the other two are from FCU and forcing the side stick which are not normal ways. The only emergency situation I can foresee is when you quickly want to take over to change the flight path and the ID button doesn't work then may be you force the side stick. The FCB in question crappy or otherwise was Airbus recommended procedure. 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.

Last edited by vilas; 30th Sep 2013 at 07:57.
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Old 30th Sep 2013, 12:40
  #40 (permalink)  
 
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Manual flight implies direct control input- i.e via the yolk in a Boeing, and that would NOT be a normal input while the A/P was still connected
It could be argued the above comment is in contradiction to the flight technique for severe turbulence.

The B737 Supplementary Procedures recommends the autopilot be set to CWS mode. The pilot then is required to manually "fly" the aircraft through the CWS mode. Control forces are slightly higher than in no automatic flight, which in turn decreases the potential for over-controlling in gusts. This is especially important at high altitude where rapid use of aileron causes spoiler actuation and the scene is set for over-controlling by the pilot.

Last edited by Centaurus; 30th Sep 2013 at 12:42.
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