TAM A320 crash at Congonhas, Brazil

[TyroPicard]

bseiker

1/ Using manual braking alone as a signal to deploy ground spoilers will not work, as brakes may inadvertently be pressed in flight when making rudder inputs.

Agreed. Also, we taxy out with ground spoilers armed - they would operate every time we used the brakes and are presumably not designed for that over their life.

2/ Combined with any of the "on-the-ground" conditions (wheels spinning or (MLG struts compressed and RA <6ft)) it looks like a good idea. We'd still need to consider the late-go-around ("touch and go") scenario, in which rudder inputs may be needed, and brake inputs may occur, and ground spoiler deployment would be fatal.

For the "rejected landing" in Airbusspeak/touch and go, the ground spoilers will retract if one thrust lever is advanced above 20° .. so that's already taken care of.
But they would still operate taxying out..... and would be extended if you held on the runway with the brakes on .. this might lead to taxying out with them "not armed" .. could they be forgotten thus adding to the risk?
Regards, TP

[bsieker]

Originally Posted by TyroPicard

For the "rejected landing" in Airbusspeak/touch and go, the ground spoilers will retract if one thrust lever is advanced above 20° .. so that's already taken care of.

Agreed. Here we're talking about precisely the case where one thrust lever is above "near idle", but manual braking should still deploy ground spoilers.

So we consider very late rejected landing, immediately before or after touchdown, possibly one engine out, thus one thrust lever at idle, the other at TOGA, inadvertent brake inputs while compensating for asymmetric thrust with the rudder.

Ground spoilers or no? Probably no, because of TOGA.

But if the PF did not set TOGA thrust, thus one lever at idle, one at MCT (standard setting for A/THR with one engine out). (Remember Sochi, where the pilot perfomed a go-around without setting TOGA thrust, albeit at higher altitude.)

Compare to this case:

One thrust lever at reverse, the other at CL, manual braking.

Ground spoilers or no? Perhaps yes, because of reverse ...

We must be very careful about the conditions under which to deploy the ground spoilers. Is there a possible credible scenario with one TL at reverse, the other at cl, brake pedals pressed, where one does not want to stop?

But they would still operate taxying out..... and would be extended if you held on the runway with the brakes on .. this might lead to taxying out with them "not armed" .. could they be forgotten thus adding to the risk?

We speculated before about the risk of failure to deploy ground spoilers when rejecting takeoff with two reversers inop, where SOP usually appears to be not to select reverse. So not arming ground spoilers for taxiing, forgetting to arm for take-off, and not selecting reverse in a reject: No ground spoilers during reject, which sounds like a very bad idea.

This problem, though, might be taken care off by the ground spoiler conditions during rejected take-off, namely wheels spinning >72kts, which would again allow for them to be armed during taxiing.

Bernd

[TyroPicard]

I thought you were considering a "normal" rejected landing as opposed to a TAM situation.

But if the PF did not set TOGA thrust, thus one lever at idle, one at MCT

MCT is above 20? so no ground spoilers.

Is there a possible credible scenario with one TL at reverse, the other at cl, brake pedals pressed, where one does not want to stop?

No - it's incredible.
Tyro

[bsieker]

Quote:

Is there a possible credible scenario with one TL at reverse, the other at cl, brake pedals pressed, where one does not want to stop?

No - it's incredible.

So, this might be a case for extending the ground spoiler logic to become:

A/C on ground
AND ((One T/L in reverse and other T/L in reverse or at or near idle)
OR (ground spoilers armed and both T/L at or near idle)
OR (one T/L in reverse and brake pedals pressed))

Excluding one at CL and one at idle, because that might happen with one engine shut down, even not wanting to land.

Perhaps one should also exclude one T/L at TOGA, because it would again be too ambiguous.

Whether or not this makes more sense than changing training procedures and/or memory items is not my call to make.

I may write up all my considerations about ground spoilers and thrust reversers and thrust levers in more concise form (standing on the shoulders of PBL's "classic" paper).

Bernd


P. S. To all those thinking we are defending Airbus at all costs: this should make it clear that we are not. No product created by mere mortals is above criticism, but it should be founded on more than saying "I am convinced non-moving thrust levers are bad!"

[DozyWannabe]

Again though, the more complex you make the logic tree, the higher chance you have of an error manifesting. This is aside from the fact that there are no doubt many occasions where you don't want spoilers to deploy, so if they did deploy on one occasion after your suggested update was made, would there be a similar outcry to roll back that change?

The problem with responding to these accidents emotionally is that by nature we want to do everything to stop that particular set of holes in the cheese from lining up again. Where we need to be careful is to make sure that by closing those holes, we're not opening others elsewhere.

I think there needs to be some kind of HF research into how a broad cross-section of pilots respond to that situation and the call-outs made. If a significant number of pilots only retard one TL by mistake, then we have a serious interface problem. If not, then it could be argued that it was just a combination of tragic mistake and dumb rotten luck. Something that factors in all too many aviation accidents.

[bsieker]

Originally Posted by DozyWannabe

This is aside from the fact that there are no doubt many occasions where you don't want spoilers to deploy

I fully agree.

That is why I have a strong resistance to quick changes to these things. But the GS logic has already been changed once, and here may (or may not) be another case for a change.

I am also very aware that ground spoiler deployment in any case other than performing a full-stop landing or rejected take-off is a Bad Thing.

I'm not saying "this should be done", but it is worth considering.

Limiting ground spoilers to cases (in addition to the existing ones) where brakes are pressed (possibly only above a threshold not commonly achieved during rudder action) and at least one thrust lever is in reverse seems to be a good safeguard. Additionally, not deploying GS if at least one thrust lever is at TOGA seems worth considering, since TOGA would never be applied during a full-stop landing (except on a carrier landing, but that is a completely different domain). It is doubtful anyway, that anything, even ground spoilers, could save you if one engine was at full reverse, and the other at TOGA.

It may be that I have forgotten a case or that I am wrong on this, and this is what peer-review is for, and why I am posting this publicly.

TyroPicard (an experienced pilot on type) already said it is unthinkable that one would select reverse and press the brakes but did not want to stop. I take this as an indication that I am not too far off the mark.

Bernd

[Lemurian]

of loss of braking

bsieker,

I had asked experienced A320 flight crews for what situations exactly said memory item was trained:
Only failure of autobrake after it had initially been active?
And/or failure of manual brake if no autobrake was selected?
Also in a case like this where autobrake fails to engage because of failure of GS deployment?
For the third case the memory item would to be more aptly called "NO BRAKING"

In the FCOM and QRH manual I'm using :

LOSS OF BRAKING

> if AUTOBRAKE selected :
PF BRAKE PEDALS............... DEPRESS
> if brakes inoperative :
PF REVERSERS....................MAX
PF BRAKE PEDALS................RELEASED
PNF A/SKID & N/W STEERING...OFF
PF BRAKE PEDALS................DEPRESS
PF BRAKE PRESSURE.............UNDER 1000 PSI
............................................................ .............................................
The first item comes on the realisation that autobrake is not operating, which emphasizes the importance of the *DECEL* or *NO DECELERATION !* call out. And by extension it takes care of the third item (CGH) where the autobrake was not functioning as selected.
Semantics can be precious sometimes : *NO BRAKING* should be used in cases where the system fails to operate as expected, whereas *LOSS OF ...* implies that a system is functioning before it then fails.
[I was there...] the scenario above (no decel then no brakes) makes a very interesting sim session on a cat IIIB autoland with 75m RVR...a very good way to determine if a crew functions optimally.
TyroPicard,

But they would still operate taxying out..... and would be extended if you held on the runway with the brakes on .. this might lead to taxying out with them "not armed" .. could they be forgotten thus adding to the risk?

I agree with your train of thoughts but normally the G/S should extend on a rejected takeoff regardless of the G/S lever position.

[Al Zimer]

Rob21
Thanks for the reply and the correction - my mis-reading of the transcript.
Yes - I see the point you are making. Particularly as there was heavy rudder usage starting about 18:48:26.
So just what was he feeling? Intriguing.
(From a non-pilot showing his ignorance.) At what stage of a landing would the PF remove his hand from the TLs?

[Dani]

At what stage of a landing would the PF remove his hand from the TLs?

Never!

____________________________________________________________ ____________
Pprune software says this reply is too short, but hey, there isn't one word more to spend!

[Gullyone]

I think that most pilots remove their hands from the thrust levers just prior to touchdown, having first closed them.

[Dani]

Nope, only Non-Airbus pilots do that. Since you fly your sidestick, you don't need your second hand anymore. You could put it on your knees, but there it doesn't help anything, hence you leave it there on the thrust levers.

This is another indication that the TAM's captain mindset was somewhat in "another aircraft". It might be justified in
some other aircraft not to touch a "broken" thrust reverser or to take your hand away from them. But as a genuine Airbus pilot you leave it there and realize that you should retard them.

btw Airbus just reissued the FCOMs for reverser fault, explaining that it's essential to retard. If the reverser fault comes on in flight, go to idle. If you execute an RTO, go to full reverse.

Dani

[Lemurian]

Rubbish !

I think that most pilots remove their hands from the thrust levers just prior to touchdown, having first closed them.

Nope, only Non-Airbus pilots do that. Since you fly your sidestick, you don't need your second hand anymore. You could put it on your knees, but there it doesn't help anything, hence you leave it there on the thrust levers......(etc...etc...)

Dani,
Are you really a pilot, even a private pilot, or even a student pilot ?

[Gullyone]

Dani, thanks for that, I have never flown the ab, I have learnt something new.

[PBL]

Originally Posted by DozyWannabe

Again though, the more complex you make the logic tree, the higher chance you have of an error manifesting.

I don't think this is quite right. If you were talking about dynamic decision-making, then I would agree that the more complex the decision tree, the more chance one has of barking up the wrong branch.

But we are talking about the system logic, and the complexity of the logic bsieker, TyroPicard and Lemurian are discussing is well within the scope of those examples which can be exhaustively checked for errors using common formal mathematical verification techniques.

Whether anyone does so, though, is another matter.

And of course what one *cannot* verify mathematically in this case is whether one has exhaustively covered all the environmental scenarios in which this logic will operate.

PBL

[Hunter58]

@Lemurian

I can guarantee you Dani is a pilot, actually an A320-family qualified Captain. So before you say 'rubbish'...

[Dani]

Lemurian, I'm very very, veeery disappointed by your remark. Are you telling me that you do not agree?

After a few posts of yours I was more like the opinion that you understand a little bit of aviation, unlike a lot of others in the thread.

And, - ... yeeeaaah, I have a few thousand hours spent on the left hand seat of Airbus. Do I need to draw you a picture of it or do you believe it??

Dani


Thanks, Richi ;-)

[Hunter58]

You're welcome... :-)

[TyroPicard]

Lemurian

I agree with your train of thoughts but normally the G/S should extend on a rejected takeoff regardless of the G/S lever position.

Yes but if not armed there will be a delay until reverse thrust selection - which adds to the risk. And if you forget reverse as well.............

And just to clarify some of the more ludicrous recent postings from the land of the cuckoo clock... PF keeps his hand on the T/L throughout the landing roll, because he is using that hand to select and cancel Reverse Thrust.
Tyro

[Gullyone]

Not so, most airline sops require the pnf to operate the rt at least on non ab
types. As the supposed ab pilots seem to disagree as to who does what, can someone who knows tell us the answer

[HotDog]

Not so, most airline sops require the pnf to operate the rt at least on non ab types.

Gullyone, which airline are you flying with? Am I correct in assuming you mean reverse thrust (rt) above?

I have 18,000 hours in various jet transports plus 2,000 odd in simulators, checking and training. Yes PNF handles rt, like in communications but PF flies the airplane until you are on chocks. I would love to see those SOPs that say otherwise.