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ATSB report just published on A320 throttle asymmetry incident

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ATSB report just published on A320 throttle asymmetry incident

Old 22nd Jan 2013, 07:49
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ATSB report just published on A320 throttle asymmetry incident

The report:

Investigation: AO-2012-022 - Inadvertent thrust lever asymmetry during the take-off roll involving an Airbus A320, VH-JQX

It is well written and well worth close study. It took a year to publish which is surprising for such a relatively simple incident. Seems during the takeoff roll a small asymmetry between the two thrust levers was noted. The left seat pilot was under training for a command while the right seat occupant was his instructor. Without going into details here (see the ATSB full report), the captain under training heard what he thought was the word "Rotate" from the instructor (PNF) and commenced rotation before realising the airspeed was still 20 knots below the correct VR. The aircraft became airborne but the pilot was able to pick up speed by reducing the climb attitude.

Rotating on the call from the PNF of "Rotate" is something often seen in simulator training even though the airspeed indicator of the PF shows well below the correct VR. It goes to show that the word "Rotate" in a firm voice can very much sound like a command, rather than just a support or advisory call by the PNF. Of course, in real life and no significant airspeed difference between the two main ASI's, "Rotate" is invariably ties in with what the PF expects to see on his ASI.

In the old days, the calls were simply "V1.....VR". Boeing changed "VR" to the new term of "ROTATE" and while that has been in use for decades I wonder how many unreported incidents have ocurred where "Rotate" called in a firm voice has caused momentary confusion if an ASI defect is present and the tendency is to respond to a firm voice (in this case "ROTATE") rather than on a correct bugged airspeed.

But there is a powerful tendency to start rotating at the word "Rotate" depending how forcefully the word is annunciated and despite the fact the airspeed on the side of the PF has not yet reached the correct VR. In other words, because things happen so fast approaching VR, it is a human factor problem where it is all too easy to act on the PNF's support call rather than rotate on the bugged VR on the PF's ASI.

In the simulator, this is most likely to occur when the instructor introduces an airspeed error between the two main ASI's with the PNF calling "rotate" on his own ASI despite the airspeed of the PF being nowhere near VR. Invariably we observe the PF then start pulling back on the control column in momentary confusion even though his ASI may be nowhere near his bugged airspeed. This is where it is good airmanship to be aware of the expected ground speed at VR as a double check.

ATSB missed a good opportunity to emphasise the need for the PF to plan on rotating on his own ASI bugged VR and treat the PNF support call of "Rotate" as purely advisory. if the PF reaches his own bugged VR speed but fails to get a support call from the PNF for whatever reason, he simply rotates (a quick glance at the ground speed indication is wise at that point). There should be no confusion and the problem sorted out at a safe altitude.

Last edited by A37575; 22nd Jan 2013 at 08:05.
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Old 22nd Jan 2013, 09:06
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Every so often you com across some gold on PPRuNe.

This is just such an occasion.

It certainly makes me think.
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Old 22nd Jan 2013, 09:12
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Pay peanuts........
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Old 22nd Jan 2013, 09:58
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This is where it is good airmanship to be aware of the expected ground speed at VR as a double check.
How would you propose to observe that groundspeed?

For me, I scan the ASI along with temps and centreline until I am crosseyed by which time it must be time to haul back. Non standard calls during the roll are extremely difficult for just this reason.

By the way, tell me about these throttles? What sort of jet engine uses carburettors?
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Old 22nd Jan 2013, 13:01
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[QUOTEHow would you propose to observe that groundspeed?
QUOTE]

If you don't know where to find the ground speed you need refresher in the sim

If you have not heard of autothrottles ditto above
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Old 22nd Jan 2013, 13:50
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A37575

ATSB missed a good opportunity to emphasise the need for the PF to plan on rotating on his own ASI bugged VR and treat the PNF support call of "Rotate" as purely advisory. if the PF reaches his own bugged VR speed but fails to get a support call from the PNF for whatever reason, he simply rotates (a quick glance at the ground speed indication is wise at that point). There should be no confusion and the problem sorted out at a safe altitude.
Right on the button. Three cheers to that man!
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Old 22nd Jan 2013, 14:47
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If you don't know where to find the ground speed you need refresher in the sim
If you have not heard of autothrottles ditto above
Thanks for illustrating my point. If the PF has time available to look at the GS on the panel then he or she could just as easily look at the much more relevant airspeed on their side. Scanning groundspeed for rotate point is about as useful as scanning groundspeed at 100' agl on final.

Yes there is an autothrottle system sometimes also referred to as autothrust but the levers in the cockpit/flightdeck/bridge/control room/reading room/pointy end are most definately called thrust levers or power levers by the jet manufacturers I am familiar with.

Anachronism anyone?
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Old 22nd Jan 2013, 21:08
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But there is a powerful tendency to start rotating at the word "Rotate" depending how forcefully the word is annunciated and despite the fact the airspeed on the side of the PF has not yet reached the correct VR. In other words, because things happen so fast approaching VR, it is a human factor problem where it is all too easy to act on the PNF's support call rather than rotate on the bugged VR on the PF's ASI.

In the simulator, this is most likely to occur when the instructor introduces an airspeed error between the two main ASI's with the PNF calling "rotate" on his own ASI despite the airspeed of the PF being nowhere near VR. Invariably we observe the PF then start pulling back on the control column in momentary confusion even though his ASI may be nowhere near his bugged airspeed. This is where it is good airmanship to be aware of the expected ground speed at VR as a double check.
A37575 - I think you need to consider the psychology of the process. In essence, the word "rotate" could be changed to "Vr" or "banana's" - it wouldn't matter. Any call has the potential to become a classically conditioned response. What you are arguing (correctly) is for the PF to ensure he does not fall for this conditioning process, and actually cross-check against some independent system. Changing the words isn't enough. If you look at the Boeing Takeoff manoeuvre in the QRH it simply has V1 ...VR Rotate, and offers no guidance or hint of a crosscheck. The FCTM goes into elaborate details of tail clearances - again anything but the need to crosscheck ASI's.

This is a huge advantage that the HUD offers, your own ASI is right there in your field of vision, together with the tail strike warning, is worth its weight in gold.
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Old 22nd Jan 2013, 21:10
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A37575 PPRuNe at it's very best. There is no icon for 'Hats off' but consider mine doffed.

It's an old debate now, but years ago a couple of overseas companies I had the pleasure of working with used a "80 knots" callout, the idea was that it provided, well before any critical speed an ASI, engine power check and a warning of the approaching V1 speed range. I liked it and found it helpful. The GS check is also very useful, particularly when the speed tape and GS readout are on screen, but the early cross check built 'time' into equation. I still do it in my head just a quick look to make sure the power is balanced, the GS about what I'd expect and a glance at the standby, takes longer to write it out than it takes to do. Not advocating - just my slightly battered two bob's worth.

This report is interesting as it describes one of those 'sneaky' little holes in the cheese which can distract and create havoc; experience, training and discipline greatly benefit on those occasions, particularly at the pay attention end of a take off roll. All's well that ends well.
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Old 22nd Jan 2013, 21:57
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We used 80 knots as a check. I thought it was in general use.
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Old 22nd Jan 2013, 22:29
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Thumbs down

For the love of God, this was in Australia you guys are talking about. The pilots here are supposedly God's gifts. It just cannot be!

Rotating at 20 kts below Vr? Unless it is a contaminated runway with the correct take off speed computation, there is a very small V1/Vr spread. As such, it was likely that rotation was accomplished before the V1 call. I do not recall take off V speed callouts on the A320 reverting to previous practice by certain operators of F-27 whereby the only callout was " rotate " when V1=Vr!
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Old 23rd Jan 2013, 00:14
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Just as a matter of interest, what inputs are used to calculate ground speed and will it still read correctly if the ASI is in error?
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Old 23rd Jan 2013, 02:56
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Angel T/L issues

I guess after a minor 'lever assymetry' issue on take off ( and by the way as the detentes wear out it gets even easier to not quite have them both/ all four in the slot, thus generating the assym ecam and requiring a minor amount of fiddling on the odd occassion ). The next thing we might see in an ATSB report is the use of FLEX/MCT when a flex temp is missed out, generating the THRUST NOT SET ecam as well....ending in an RTO or similar perhaps?

Both of these very minor issues IMHO should 'not result in anything more than either pushing up the levers to TOGA ( actions for the latter ECAM actually tell you what to do) or a bit of adjustment . Bearing in mind the actual thrust set will be TLA determined ,normally checked at 80 kts ( yet with no acknowledgement of the 'THRUST SET ' PNF call by the PF - which seems strange to me , but is AB standard now.) .. Then '100 kts ' as the hi / low speed RTO divider and x check etc ( or 80 kts on a Boeing if I remember)

As far as rotating 20 kts early, yes, perhaps a pavlov dog reaction , but hopefully just an ease off of the pitch rate would have prevented any tail strike as with both engines operating the jet would pretty quickly be there anyway.

To be honest , if they did not bend the jet or generate a QAR event which they had to answer to the safety department for, it is hardly worth even being a reportable incident in my view... Simply a debrief item to learn from ...well done for the crew coming forward if they did so voluntarily as it has generated some good discussion.

But this is Australia And we do like to get wrapped around the axles for trivial issues...Go work overseas for a while and see how bad things have to get to hit the papers!!!
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Old 23rd Jan 2013, 03:08
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This is not that different to other incidents where the gear up was called for and the flaps were raised instead. It all boils down to the age old communication problem of what was said being different to what was percieved. Mandating use of the interphone I think would help mitigate that problem. A jet cockpit is still a noisy work environment and as both pilots are looking out the front, the other cues that help a person decipher what is being said by the other person are not present. At least using the interphone what is being said is heard in the headset and not a distorted bunch of words coming from the other side of the cockpit.

I would imagine that the Training Captain got a nasty shock when the nose started coming up in response to his "Go..TOGA" command.
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Old 24th Jan 2013, 04:47
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I think you need to consider the psychology of the process. Any call has the potential to become a classically conditioned response.
Especially if that call comes from a Training Captain in the RHS!
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Old 24th Jan 2013, 05:02
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Mandating use of the interphone I think would help mitigate that problem
Interesting. Are there any jet operators in Australia that do not use headsets & intercom as standard below transition? Maybe not mandated but always used?

A jet cockpit is still a noisy work environment and as both pilots are looking out the front,
Both looking forward? Not sure I agree. As PF I am trying to keep the beast on the centreline, scan speed and temps, when the FO is the handling pilot the same as well as being ready to take-off for an RTO.
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Old 24th Jan 2013, 05:29
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Headsets always on below cruise altitude.

Interphone is optional.

Most guys don't use it, however overseas operations can require both speakers on ears and interphone on.
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Old 24th Jan 2013, 09:13
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Geragau, I agree with you completely. If one does not receive the V1 call but only the call to " rotate ", something is definitely not right...cause for pause, query and a quick crosschecking. For these two highly experienced pilots to be caught in this incident is highly troubling.
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Old 24th Jan 2013, 18:18
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Both looking forward? Not sure I agree. As PF I am trying to keep the beast
on the centreline, scan speed and temps, when the FO is the handling pilot the same as well as being ready to take-off for an RTO.
Agreed but where is most of your focus?

the other cues that help a person decipher what is being said by the other
person are not present
The rest of the statement puts the first part in context.

Interphone is optional.
A headset without using the interphone actually hinders intercockpit communication. One ear is covered and the other is not so its not surprising that in this instance the PF misinterpreted what was said by the PNF.

For these two highly experienced pilots to be caught in this incident is highly troubling
Doesn't matter how experienced you are as an F/O, when you are doing Command training on a new type you are on a steep learning curve and mistakes will occur. The Training Captain can't anticipate every unexpected response if he hasn't experienced it previously.
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Old 25th Jan 2013, 01:47
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As a mere PPL two things come into my head; would they not have calculated the proposed take off roll, and would this not be able to be gauged by the amount of runway used up, and, would it not be unheard of to glance at the ASI before committing to becoming airborne?
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