PIA A-320 crash in Karachi

[mtr75 653]

58 minutes ago, Chock said:

As far as I'm aware that sound you can hear on the ATC recording is the landing gear overspeed warning chime. This is consistent with what we know about the situation, i.e. that they were too high and too hot, but instead of abandoning their approach, kind of went 'yeah, we can make it'.

So they stuck it in a dive, presumably hoping the gear and flaps would brake them on the descent. Unfortunately, what that warning chime means, is that you are over the speed at which the landing gear actually will deploy (over 250 knots), so it's not warning you about overstressing the gear because it is down (which I bet that's what they thought it meant), it's warning you that you are too fast and it's not gonna lower it at all. That's probably why they tried to touch down, thinking that the gear was actually down because the lever was down. 

If you think about it, this means it is quite likely the engine nacelles touched down at a speed near to 250 knots nearly halfway down the runway. At that speed, they probably would have blown or set fire to the tires anyway even if the gear had been down; that's faster than Concorde takes off at, and it has tires specially rated for its speed. If you've ever opened the engine cowling panel on an A320, you'll know they are not thick heavy metal, they'd have worn completely away in a second or two, exposing the bottom of the engine to friction damage and likely destroying the accessory drive mechanisms.

This would explain why they still had the airspeed necessary to get back into the air (I don't think that MiG 29 was doing 250 knots when its pilot raised the gear too early) and also probably why the gear came down after they had lifted off the runway because their speed bled off to less than 250 knots on the climb out with engines spooling down, and the gear handle would still have been down, which would then allow the gear to descend. Unfortunately, at that point they'd have been better off if the gear actually had not come down, from the point of view of wanting to be in a clean config to stretch the glide a bit more and actually really intentionally try a belly landing.

Totally agree they had enough energy to get airborne again even with fatally damaged engines. The gear tho N.C. is weird too. I agree it’s totally possible they put the lever down but the gear wouldn’t go down, but for Pete’s sake that’s why you say “gear down and indicating”. The list of things these guys did wrong is long and distinguished. 

[Chock 17,769]

Just now, mtr75 said:

Totally agree they had enough energy to get airborne again even with fatally damaged engines. The gear tho N.C. is weird too. I agree it’s totally possible they put the lever down but the gear wouldn’t go down, but for Pete’s sake that’s why you say “gear down and indicating”. The list of things these guys did wrong is long and distinguished. 

Well this is where speculation has to leave off and the FDR and CVR will tell the tale. I would think that training records for the crew, health and condition of the crew, CRM and issues related to this will be featuring heavily in the investigation. There have unfortunately been cases where, for example, an overbearing skipper has prevented a subordinate co-pilot from speaking up or contradicting a more experienced pilot even when they are doing something which is blatantly not safe. But we won't have any access to that kind of investigative information for quite a long time.

And before we completely condemn the crew for having been totally responsible for the accident, although this admittedly is looking increasingly likely, the condition of the aeroplane from maintenance records and what the FDR can reveal will also have to be looked at very closely. Many aeroplanes have been standing around doing nothing for weeks and many will have had a good deal of maintenance carried out during this period since the opportunity has somewhat uniquely presented itself for this to occur around the entire world airliner's fleets, but also it has been a situation in which such maintenance has been carried out in unusual - in fact unique - working circumstances given the requirements for social distancing. Thus the possibility that some of this maintenance could have been done incorrectly is something which will need to be eliminated as a contributory factor. Not saying it was, but it is something which may possibly have had a bearing on why the aeroplane was being flown in the way it was.

[Christopher Low 5,352]

You can say what you like about maintenance records, but if there was nothing wrong with the aircraft on that first approach, then attempting a landing from 3500 feet at 5 nautical miles out was absolutely crazy, and not something that an experienced airline captain should even be thinking about. I really cannot understand that.

[him225 51]

A botched go around looks more plausible, with the chime sound relating to flap overspeed. Can't imagine pilot continuing high on final approach at ~250kts in hopes of slowing down to landing speed down to the airport, so as to have the heard chime to sound for landing gear protection and the gear extension confusion to follow. Engine can be heard spooling up in one pilot to atc message post go around, so they were not immediately failed on impact with ground.

Edited May 25, 2020 by him225

[JonP01 104]

I thought this makes for some interesting reading (at least for someone like me who is not familiar with the airbus systems).

https://safetyfirst.airbus.com/app/themes/mh_newsdesk/documents/archives/a320-landing-gear-downlock.pdf

[threexgreen 3,139]

16 hours ago, mtr75 said:

The approach was inexcusable. At 3,500 feet and 5 miles out, you have no chance of making the runway using a stabilized approach. I mean they got a flap overspeed warning on final. That’s just inconceivable. SOP for any 121 carrier is that if the approach is unstable, go around. It’s just automatic. And they knew for darn sure the gear wasn’t down when the engines hit the deck.  

But that's what I said. I agreed on number 1 to abort the approach. My point is without the CVR and FDR data there's not really a way to judge the decisions taken after the ill-fated 'touch down' because I would say it was a warning concert going on with systems failing and ultimately the engines shutting down. Couple that with the process of realizing or trying to realize what just happened on that runway and I'd argue that you're at the limit of what's humanely possible in terms of dealing with a situation mentally pretty fast. After going around it was just a matter of trying to keep the thing in the air and reach that runway somehow.

So while the decision to keep going on that highly unstable approach was utterly inconceivable (unless a good reason is found during the investigation) and in that way clear pilot error, I don't think there was much they could have done after they went around given all the mental capacity was likely just exhausted by trying to maintain altitude. I'm not sure you would be thinking of the military field in a moment like that for example.

[threexgreen 3,139]

Here's a graph of the descent profile from FL100 onward, courtesy of a poster on PPRUNE via FR24. They were racing down already from FL100 with something of a 6000-ish fpm rate to capture the glide slope. 4 minutes from FL100 to 'touch down'. Talk about chasing that descent path.

[Chock 17,769]

That graph's plot is actually nearer 4,000 fpm, but I agree that is still undeniably a hot and high approach for an A320 descent so close to the runway. It is absolutely a situation where going around would have been not only prudent, but almost certainly I should think a P.I.A. S.O.P. requirement. As long as you have the speed under control, there is technically nothing wrong with coming down at those rates, other than the possibility of some serious ear popping in the cabin, but it's not where you want to be when so close to the airport and trying to get things stabilised for an approach.

Anyone who ever flew on what was kind of the A320's predecessor - the Dassault Breguet Mercure's of Air Inter - will know those things could really descend at a very steep angle and would quite often come down at well over 6,000 fpm (that's what you get when a jet fighter manufacturer has a go at making an airliner I guess), so it's not unknown for airliners to be coming down at these kind of high FPM counts, but these are usually down from cruise altitude to the point where the crew are preparing to stabilise things as they head for an  initial approach point, rather than actually trying to get the thing stable whilst coming down like grand piano with lead weights tied to it.

Hate to say it, but this incident is really looking like a case of absolutely crazy piloting.

Edited May 25, 2020 by Chock

[threexgreen 3,139]

33 minutes ago, Chock said:

That graph's plot is actually nearer 4,000 fpm, but I agree that is still undeniably a hot and high approach for an A320 descent so close to the runway.

-4000 fpm on average from FL100 downward, yes. But you can see the descent rate goes to over -6000 fpm (close to -8000 fpm) at glide slope capture and that's just a no-no. You can also see another dip to above -2000 fpm while on final which is again well over the limit, commonly not more than -1000 fpm descent rate on approach. Factoring in the speed as well which presumably kept the gear from extending this is bordering on criminal negligence to be honest.

33 minutes ago, Chock said:

It is absolutely a situation where going around would have been not only prudent, but almost certainly I should think a P.I.A. S.O.P. requirement.

I guess that's what the PIA spokesperson was referring to when they said the crew didn't follow SOPs.

Edited May 25, 2020 by threegreen
Added the minuses.

[Chock 17,769]

Yup, any way you paint it, it's not a great bit of flying. Expect this to be the subject of one of those Air Disaster TV shows soon.

[SAS443 1,722]

2 hours ago, Chock said:

other than the possibility of some serious ear popping in the cabin,

The cabin pressure controller onboard the Airbus regulates max VS to -750fpm during descent in the auto-mode. Thats as bad as it gets. Upon landing (which was a pipe dream, sadly), any residual pressure is released at 500pm rate (your standard descent rate in a Cessna or Piper)

Edited May 25, 2020 by SAS443

[n4gix 4,947]

21 hours ago, threegreen said:

I do believe that's what is known colloquially as a "Dive and Drive" approach...

[mtr75 653]

7 hours ago, threegreen said:

But that's what I said. I agreed on number 1 to abort the approach. My point is without the CVR and FDR data there's not really a way to judge the decisions taken after the ill-fated 'touch down' because I would say it was a warning concert going on with systems failing and ultimately the engines shutting down. Couple that with the process of realizing or trying to realize what just happened on that runway and I'd argue that you're at the limit of what's humanely possible in terms of dealing with a situation mentally pretty fast. After going around it was just a matter of trying to keep the thing in the air and reach that runway somehow.

So while the decision to keep going on that highly unstable approach was utterly inconceivable (unless a good reason is found during the investigation) and in that way clear pilot error, I don't think there was much they could have done after they went around given all the mental capacity was likely just exhausted by trying to maintain altitude. I'm not sure you would be thinking of the military field in a moment like that for example.

This military field option thing is pure fantasy. Nobody ever thinks, “gee, if I cock up the approach and get launched back into the air because I’m going 250 knots at touchdown, at least there’s a military field 3 miles ahead”. I’m not being critical of you, but I’ve heard this thrown out there on other forums, and it’s just gibberish. Once they touched down they had one option. They didn’t take it. 

[mtr75 653]

5 hours ago, threegreen said:

-4000 fpm on average from FL100 downward, yes. But you can see the descent rate goes to over -6000 fpm (close to -8000 fpm) at glide slope capture and that's just a no-no. You can also see another dip to above -2000 fpm while on final which is again well over the limit, commonly not more than -1000 fpm descent rate on approach. Factoring in the speed as well which presumably kept the gear from extending this is bordering on criminal negligence to be honest.

I guess that's what the PIA spokesperson was referring to when they said the crew didn't follow SOPs.

A stable approach is not more than 1,000 fpm descent and speed +/- 10 knots VREF. They exceeded both by extremely wide margins. Just absolutely inexcusable. 

[JonP01 104]

If passengers were not already uncomfortable from the physical sensation of such an unfamiliar descent profile, they sure would have been in that 20 seconds from 9:32:43 where it lost almost 2,000 ft of altitude. I think if any of us were on that flight we would have been wanting answers at 8,000 ft.