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Catching a late sink by manual thrust in an A330.

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Catching a late sink by manual thrust in an A330.

Old 11th Jul 2017, 13:12
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Catching a late sink by manual thrust in an A330.

A Malaysia Airlines A330 became unstable at low altitude during its landing at Melbourne Airport, Australia on 14 March 2015. The landing was hard requiring landing gear replacement. Part of the ATSB report said: "At 60 ft. AGL, the captain moved the thrust levers forward momentarily into the TOGA detent. He told the investigators that this was done in response to a feeling that the aircraft was sinking below the path, and the intention was to reduce the sink by applying more thrust to the engines."
The report said at the time of the occurrence there was no procedure on the A330 for the use of manual thrust for this purpose.
One of the findings published by the ATSB was "the captain used an unapproved manual thrust procedure in an attempt to recover the approach."

While this writer has never flown an Airbus type, I cannot understand the logic of that finding by the ATSB. On countless occasions when flying the Boeing 737, there were times a sudden late sink caused by wind shear below trees was caught by timely application of manual thrust. Is that wrong technique on an A330?

Could someone please explain what ATSB means when it says "the captain used an unapproved manual thrust procedure in an attempt to recover the approach?" What is the difference in the A330 between an approved manual thrust and a unapproved manual thrust procedure?
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Old 11th Jul 2017, 13:42
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Setting TOGA puts the aircraft into Go Around mode so a lot of things happen. It changes the flight guidance modes and I'm not sure but it might affect the logic of the flight control laws so perhaps it would be no longer in the flare mode, so no longer transitioning from normal to direct law for the landing.

The highest amount of thrust that would have been appropriate would have been the Climb Thrust limit (two clicks less than the TOGA detent on the thrust levers), if he felt he needed more thrust than that, a go around would have been the correct option rather than continuing with the landing.
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Old 11th Jul 2017, 13:54
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Originally Posted by sheppey View Post
While this writer has never flown an type, I cannot understand the logic of that finding by the ATSB. On countless occasions when the 737, there were times a sudden late sink caused by wind shear below trees was caught by timely application of manual thrust. Is that wrong technique on an A330?
Do you have a link to the report?
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Old 11th Jul 2017, 14:23
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Done it dozens of times in the 330. (not TOGA, mind you, just a handful of extra thrust for a second or two). What on earth is wrong with that when you are getting low on the speed-tape?
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Old 11th Jul 2017, 15:28
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Originally Posted by giggitygiggity View Post
Setting TOGA puts the aircraft into Go Around mode so a lot of things happen. It changes the flight guidance modes and I'm not sure but it might affect the logic of the flight control laws so perhaps it would be no longer in the flare mode, so no longer transitioning from normal to direct law for the landing.

The highest amount of thrust that would have been appropriate would have been the Climb Thrust limit (two clicks less than the TOGA detent on the thrust levers), if he felt he needed more thrust than that, a go around would have been the correct option rather than continuing with the landing.
If the aircraft had autothrust on, then the thrust levers were already in the climb detent. You could move the thrust levers momentarily out of the detent (not setting them in any detent) or you could put them on the FLX/MCT for a couple of seconds. But as giggity says, never in the TOGA detent. Not if you plan to land anyway
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Old 11th Jul 2017, 16:08
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Disqualification:
Not on A330 but I think A320 is similar enough.

TL/DR:
Assuming auto thrust was on, the pilot should have pulled back the thrust levers "a bit" (somewhere between 1.05 and 1.2 EPR, but that is for me), pushed the Auto Thrust (instinctive) disconnect button, adjusted power as required and landed, OR, pushed the thrust levers to TOGA and made a Go Around.

Full story:
On the Airbus the thrust lever does not move with the auto thrust on, but will remain in the climb detent, while fadec regulates power output. The preferred method to go to manual thrust is:
Pull thrust lever back until thrust lever angle matches engine output (there is a blue marker on the engine instrument to help with this), push (instinctive) disconnect button to switch auto thrust off. While the levers are being pulled back the auto thrust is regulating power output with an upper limit set by the thrust lever angle.
If the thrust lever is pulled back to the idle stop the auto thrust switches off.
On the approach with auto thrust on (the norm for most Airbus landings), the levers stay in the detent until around 30' radio altimeter. Then the Airbus calls you a retard and you pull the lever to the idle detent.
This is different from most other aircraft where the power lever will be moved by the auto thrust system, and the pilot can manually override the system by holding/moving the power lever.
On the Airbus there is no approved way of "helping" the auto thrust with manual thrust lever input, if the lever is pulled back out of the detent with auto thrust on, it will generate a warning (LVR CLB) to remind you to stop interfering, Airbus wants it on or off.
If the Airbus pilot needs MORE thrust than the auto thrust is providing the normal way to do it is PULL BACK ON THE THRUST LEVER and disconnect auto thrust. This is not instinctive to most pilots.
Of course there is times were you would need so much extra power you would not pull back on the thrust lever before disconnecting, but if that happened at 60' probably a go around should be made anyway.

If you put the thrust lever in the TOGA detent several things happen:
The auto thrust switches off, and thrust increases (dramatically) to maximum available.
The flight director goes to go around mode (if the Airbus was not in clean configuration), and will pitch up if autopilot was on.
The Airbus will transition to flight mode if in flare mode. You should not land in flight mode because the fly by wire system is not designed to do this.

Last edited by hans brinker; 11th Jul 2017 at 16:27. Reason: Spelling, adding info
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Old 11th Jul 2017, 16:26
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Its a technique called thrust bump and no longer in our FCTM. The logic is as follows:
The thrust levers don't move when A/T is active in the CLB detent. The actual thrust being commanded can be anywhere from idle to CLB.
The A/T disarms when moved to MCT, but rearms if moved back to CLB.
So if the pilot anticipates that the a/c is going to run low on energy (sinking feeling), he/she can preempt the A/T by momentarily moving the levers from the CLB detent to the MCT detent and immediately back again. You get a nice surge of thrust as the A/T disarms and starts to run up to MCT, then back towards idle (or stays near climb if your hunch is correct and the speed starts trending low) as A/T rearms when you place the lever back into CLB.
There are 2 big issues with the techinque. Firstly it is somewhat destabilizing if you do not have a good feel as to how much energy the bump will add to the approach. Second issue is the A/T do not rearm below 100ft, so if you do this below 100 you should not move the levers back to climb, but straight to where you need the thrust lever position needs to be as in a manual thrust approach. Quite a few have embarrassed themselves forgetting this change at 100ft and end up blasting into the flare at +30kts.
Personally I just use maunal thrust. More simple. More fun to fly.
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Old 11th Jul 2017, 16:36
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When I saw your thread title, I was extremely curious. However, upon further reading and having discovered that it involved a Malaysian Airlines crew, I am not surprised the MLG required replacement.

The "3 L's" do come to mind on this one:

1) Lack of training
2) Lack of CRM
and 3) Luck (that the flight didn't crash/disappear/get shot down).
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Old 11th Jul 2017, 16:52
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If the SOP would have told them to use Manual thrust with manual flight, this would not have happened.
Either all ON or all OFF.
Works best in all conditions.
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Old 11th Jul 2017, 16:59
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Originally Posted by Amadis of Gaul View Post
Do you have a link to the report?


Two seconds of google:
malaysia airlines a330 hard landing

https://www.atsb.gov.au/publications...r/ao-2015-032/

From the report it seems to me more of a issue with side stick control, and !ESS of an issue with thrust. They were way. Below the path and added full nose down at 24' .......
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Old 11th Jul 2017, 17:01
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Originally Posted by Icelanta View Post
If the SOP would have told them to use Manual thrust with manual flight, this would not have happened.
Either all ON or all OFF.
Works best in all conditions.
I think most Airbus operators want ap off at on for landing, I think also 777 is always at on ..
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Old 11th Jul 2017, 17:58
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Crew Resource Mismanagement

Originally Posted by hans brinker View Post
Two seconds of google:
malaysia airlines a330 hard landing

https://www.atsb.gov.au/publications...r/ao-2015-032/

From the report it seems to me more of a issue with side stick control, and !ESS of an issue with thrust. They were way. Below the path and added full nose down at 24' .......
Yikes..
I speed read the report (an amazing job; as always ATSB..) and this has hallmarks of a textbook Cockpit Culture prang.
The PM at MAS can only 'encourage' a Go around??
My mob strongly adheres to the 'call it, honor it' philosophy. Let's not break the jet and we can talk about it later; hell, we're paid by the minute. Flight Ops & FOQA say we're still not doing enough go arounds...
The PM (FO) assumed the PF was going around and sat there silently, then decided he'd help a little with some dual input?
Airbus does stuff directly, and the rule of primacy is a very powerful thing. I understand that sinking close to the ground (especially after a long days work) fires up a very strong instinct to catch the sink with power; but thats why we train. And brief. And go around if it looks ugly. 4 red is ugly.
There but for the grace et al, and I've planted a few in my time but wow...
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Old 11th Jul 2017, 19:36
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Airbus late sink A330

Without requiring special throttle manipulation or other pilot intervention, does Hal safely catch all late sinks on A330's?
Are there any known cases where Hal didn't?
Are late sinks practiced on A330 simulators?
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Old 12th Jul 2017, 09:26
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@dogsridewith; I don't know because I never let it get to that.

There used to be an Airbus approved procedure called Phase Advance, which was to be used in those instances where the Autothrust was being 'lazy' on approach, and/or on hot thermally days, and allowing the speed trend to drop into Vls.

To engage Phase Advance, one simply pushed the thrust levers just forward of the CLB detent - NOT into TOGA, NOT even as far as MCT, but just out of the CLB detent.

Doing so disengages A/THR, (but it stays armed), so the FADECs increase engine thrust towards where the thrust levers are now set, i.e. just above CLB thrust. After one or possibly two seconds, you return the levers to the CLB detent. So the action is: Push about a centimeter, (click)*, then after one second pull back into the CLB detent, (click), upon which the A/THR re-engages.

This procedure increases engine thrust a little, (not all the way to above CLB), which is usually all that is needed, and it works well. BUT the A/THR does NOT re-engage below 100', so in this case you would have to manually control thrust into the flare and landing. However, Airbus have removed the procedure from the manuals, and there is no mention of it anywhere.

I recently did this purely instinctively on an A320 when the speed trend arrow went deep into Vls on short finals, (I was used to using phase advance on A330s on approaches on hot thermally days), although it is no longer an approved procedure.


* The (click) is the sound the lever gates make, you are not clicking any buttons.

Last edited by Uplinker; 12th Jul 2017 at 14:04. Reason: Changed wording slightly.
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Old 12th Jul 2017, 12:47
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Thanks to all correspondents who replied to my questions. Most informative.
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Old 12th Jul 2017, 16:57
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The "phase advance" is not in our books, but some check airmen still teach it since it's not "prohibited". I do it occasionally. (A320)
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Old 28th Apr 2020, 15:38
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Digging up an old thread.

https://www.youtube.com/watch?v=TMiu...ature=youtu.be

Thrust bump during the flare around 3:25.
I have never seen this before at any airline I've worked for.

In my opinion, a speed trend deep into Vls doesn't require this (unapproved?) technique as long as there's no actual drop below Vls. And if the speed does drop below Vls, a go-around is the best option.
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Old 30th Apr 2020, 14:50
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Maybe not in an A318 - I can't see his PFD clearly enough to see what the speed and speed trend is - but in an A330; if the speed reduces to more than a few knots below Vapp bug on short finals and you do nothing, you can get sink and a heavy arrival.

Phase advance is no longer a thing with Airbus, but their advice to pilots to take manual control if the automatics are not doing what you need, still holds.

Disconnecting the A/THR by pushing out of the CLB gate below 100', as this guy does, is one way of switching to manual thrust control.

I've needed it a couple of times.

.

Last edited by Uplinker; 2nd May 2020 at 09:14. Reason: clarification
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