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Manually overriding autothrust

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Manually overriding autothrust

Old 28th Sep 2013, 22:25
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Manually overriding autothrust

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.
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Old 29th Sep 2013, 00:34
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Depends what mode you're in, but on a Boeing anything, feel free if Thrust is your Speed mode and the ATC isn't keeping up nicely...... Approach as an example
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Old 29th Sep 2013, 00:55
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What pilot would not override an autopilot or autothrottle if it wasn't doing what he wanted. No competent company would ever say don't override it if neccessary. Not even Airbus.
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Old 29th Sep 2013, 01:05
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Absolutely, but if it's Speed on Pitch, then I guess you would look at other solutions
I never flew a 'Bus, but the quote sounds otherwise very odd, yeah
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Old 29th Sep 2013, 01:10
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Don't tell me Airbus actually said that. Maybe that is why AF 447 crashed. Nobody was allowed to hand fly. When the autopilot failed because of loss of IAS maybe they were not taught how to fly pitch and power because they would have to disconnect the autopilot. I know it disconnected by itself but it might have been confusing for them.
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Old 29th Sep 2013, 01:15
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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.
Can you please reference that statement.

Seems to me we violate that directive every time we're on final.

Last edited by Altcrznav; 29th Sep 2013 at 01:40.
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Old 29th Sep 2013, 01:25
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The Douglas/Boeing doesn't prohibit it and it's sound practice I believe on approach in blustery conditions, as it saves that sinking feeling when the speed washes off towards Vmin and the AT goes to warp power to prevent further speed loss.
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Old 29th Sep 2013, 01:29
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As far as 'over-riding an AP' goes, I guess we don't do that on any type really ( I have been known to change modes though, or disconnect it at times)
The 'Bus is a little unusual tho and I've heard that you don't touch the controls with the AP in ....... But then, why would you want to?
ATs are a different story tho, obviously
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Old 29th Sep 2013, 02:14
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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.
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Old 29th Sep 2013, 02:15
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Why not override an autopilot? I did whenever it wasn't doing what I wanted. I don't even care if the autopilot works so overriding it is no big deal. Hand flying is quite simple. We all did it.
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Old 29th Sep 2013, 02:20
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Don't think it's wise to override an AP, Bubs.
AT, sure at times
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Old 29th Sep 2013, 03:11
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Why is it not OK to override an AP? That kind of complacency and trust leads to accidents.
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Old 29th Sep 2013, 03:22
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A few people here are getting confused between over -ride and disconnect.
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Old 29th Sep 2013, 03:27
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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.


Last edited by JammedStab; 29th Sep 2013 at 03:31.
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Old 29th Sep 2013, 04:12
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The AT should be left alone,dont push or pull the TL when the AT is engaged.
If the AT is bit sluggish then increase the command speed and it will react,once done,reset speed to required.
Now if your AT is not behaving as it should be,(read turkish),then disconnect the and fly manually.
This overriding,push pull with full automatics on damages the AT clutch and is bad practice.
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Old 29th Sep 2013, 04:21
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At least on the Boeing I fly overriding the AP is a normal feature and will degrade its function to CWS. Our SOPs call for that in a few specific situations but it is not reserved for emergencies at all.

Overriding the AT is possible, that is why there is a clutch in the first place. But it is of course not good practice to fly the whole flight that way. However is good practice to manually override for short term speed deviations. Might be a good idea for example in mountain wave situations.
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Old 29th Sep 2013, 04:28
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However is good practice to manually override for short term speed deviations. Might be a good idea for example in mountain wave situations.
You mean disconnecting surely.
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Old 29th Sep 2013, 04:30
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Wizofoz is correct. There is a difference between overriding AP and disconnecting the AP. You cannot override the AP or ATHR in Airbus FBW. If you force the side stick the AP will disconnect anyway. But there is no restriction on taking over manually. That should be done with ID button on the stick. As the Thrust levers do not move and are static in CLB gate you cannot overide (overpower) them but you can control them manually. Airbus goden rule 2 "Use appropriate level of automation.means flying selected speed, disconnecting ATHR and using manual thrust or even flying manually if required. Rule4 "Take action if things do not go as expected" tells you to be proactive and make the aircraft do what is needed with or without automation.

Last edited by vilas; 29th Sep 2013 at 04:32.
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Old 29th Sep 2013, 10:53
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One of the classic automatic monkey event I witnessed (n the simulator thank goodness), was a experienced Chinese captain who in the 737 rolled over nearly inverted on a coupled ILS after the AT clutch motor on one thrust lever failed while the thrust levers were at idle while slowing for flap and gear extension. As the airspeed came back to Vref+5 with landing flap, the other engine went to high thrust to maintain the selected approach speed while the idle engine stayed at idle.

Instead of disconnecting the AT system and using manual thrust on both engines, the captain thought the idle thrust engine was actually an engine failure! He called engine failure and directed his F/O to shut down the engine with the failed AT clutch motor. There was nothing wrong with the engine. The AP could not cope with the huge amount of crossed controls needed to maintain the coupled ILS on one engine and disengaged itself. At no time did the captain attempt to use rudder to correct the yaw. All the time both pilots had their hands on their knees impassively watching the 737 roll on its back and go in like a bomb. The simulator was then "frozen" to prevent further embarrassment and consequent loss of face.

Last edited by Centaurus; 29th Sep 2013 at 11:01.
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Old 29th Sep 2013, 11:28
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This has happened in actual flight on China airlines 006 where crew failed to monitor the aircraft flight path during restart of failed no.4 engine. The disoriented crew let the aircraft go on the back and screaming dive loosing 30000ft in 2and a half minute. The pilot finally completed the barrol roll experiencing 5g was able to land safely.

Last edited by vilas; 29th Sep 2013 at 11:57.
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