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PIA A320 Crash Karachi

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PIA A320 Crash Karachi

Old 23rd May 2020, 13:38
  #241 (permalink)  
 
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Originally Posted by henra View Post
You might want to have a closer look at the picture in post #85
https://www.pprune.org/rumours-news/632693-pia-a320-crash-karachi-post10790064.html
If you look at the nacelles it is clear this wasn't just an oil leak. They are torn on the bottom. Those pods 100% scratched the tarmac. At a nose high attitude.
surprising it didn’t liberate the cowls. The latches are right in the impact zone and the cowls are carbon composite... more likely to be a brief high (ish) descent rate than dragging along for hundreds of feet settling...
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Old 23rd May 2020, 13:44
  #242 (permalink)  
 
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AVH now reporting that sources within Pakistani CAA confirm ground contact was made with retracted gear on first approach, there was no communication of any fault or gear issue prior to the go-around. Sadly this confirms all that was suspected following the release of the PSPK photos.

From the wording it is not yet clear if the gear remained retracted throughout the approach, or if it was retracted before a positive climb was achieved, however the MLG doors would have been damaged if the gears were in transit while making the ground contact (Smartlynx), but no such damage is visible on the photos.
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Old 23rd May 2020, 13:52
  #243 (permalink)  
 
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Originally Posted by andrasz View Post
AVH now reporting that ground contact with gear retracted on first approach is confirmed from sources within Pakistani CAA, there was no communication of any fault or gear issue prior to the go-around. Sadly this confirms all that was suspected following the release of the PSPK photos.
Looks like unstable high energy approach & basically Messed it up by the time they realized TOGA and damage was done to the Port & Starboard side engine” scrapes , possibility is oil lines leak & flame out/ compressor stall by the time they were downwind”

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Old 23rd May 2020, 13:56
  #244 (permalink)  
 
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My 2 cents worth people,

Looking at those marks on the engines, there is no way those marks are due to contact with the runway/ground. If there was contact, there would be some rather large obvious flat spots under those engines. The angle of those marks at the trailing edge of both engine cold stream ducts would indicate that not only half of the engine exhaust cones should be missing/ground away, BUT half of the rear fuselage as well !!! IMHO.

Lets leave it to the expert investigators.

Rgds McHale.
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Old 23rd May 2020, 14:03
  #245 (permalink)  
 
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Also possible that the gear was retracted before the flaps during the go-around. Standard procedure is “Go Around - FLAPS, retract one stage, positive climb - GEAR UP.

Perhaps it happened out of sequence by mistake, “Go Around” and the wheels went up first instead of the flaps.
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Old 23rd May 2020, 14:07
  #246 (permalink)  
 
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Originally Posted by krismiler View Post
Also possible that the gear was retracted before the flaps during the go-around. Standard procedure is “Go Around - FLAPS, retract one stage, positive climb - GEAR UP.

Perhaps it happened out of sequence by mistake, “Go Around” and the wheels went up first instead of the flaps.
Not possible IMHO due to landing gear interlock.
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Old 23rd May 2020, 14:13
  #247 (permalink)  
 
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Originally Posted by metro301 View Post
No. there is no such protection
Many thanks. TT
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Old 23rd May 2020, 14:14
  #248 (permalink)  
 
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henra,
"They (engine cowls) are torn on the bottom."

Looking at a slightly magnified view of that photo, all edge surfaces appear 'torn' (top/bottom fuselage, fin) due to photo resolution / enlargement.

As per Capt McHale, extrapolating the cowl marks rearward, suggest that there should also be rear fuselage / tail damage.

whereas oil stains … follow the airflow …
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Old 23rd May 2020, 14:15
  #249 (permalink)  
 
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Too much assigning of fact to all the speculations so far.

I don't accept all the supporting arguments as real fact.

For example surely those on site know where the engine cowls are damaged sufficiently to disable the engine (runway scrapes, cowl fire damage or wear through). Cowl crushing sufficient to damage systems?

And what about past history of similar installations? Don't investigative reports have cowl runway impacts in them of similar severity?
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Old 23rd May 2020, 14:17
  #250 (permalink)  
 
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Originally Posted by Capt Quentin McHale View Post
Looking at those marks on the engines, there is no way those marks are due to contact with the runway/ground.
The ground contact marks are just two small patches on the underside of the fan cowl, the widening black marks further aft are traces of leaking engine oil.
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Old 23rd May 2020, 14:19
  #251 (permalink)  
 
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Originally Posted by lomapaseo View Post
Too much assigning of fact to all the speculations so far.

I don't accept all the supporting arguments as real fact.

For example surely those on site know where the engine cowls are damaged sufficiently to disable the engine (runway scrapes, cowl fire damage or wear through). Cowl crushing sufficient to damage systems?

And what about past history of similar installations? Don't investigative reports have cowl runway impacts in them of similar severity?
absolutely cowl crushing from impact could impart terminal damage consistent with the mishap.
//type rated and current A320 driver
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Old 23rd May 2020, 14:24
  #252 (permalink)  
 
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Not possible IMHO due to landing gear interlock
True if the aircraft had weight on wheels but the gear could have been retracted just prior to ground contact or just after becoming airborne again. Airbus procedure is not to retract the undercarriage during a wind shear encounter as the initial drag penalty is significant. I’m not suggesting W/S was a factor, just using the procedure as an example of the drag retracting gear creates on the A320.
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Old 23rd May 2020, 14:25
  #253 (permalink)  
 
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Originally Posted by Capt Quentin McHale View Post
My 2 cents worth people,
Looking at those marks on the engines, there is no way those marks are due to contact with the runway/ground.
May I remind you of these words once the final report is out?
If there was contact, there would be some rather large obvious flat spots under those engines.
Those cowlings are only thin covers. Underneath is the massive structure designed to contain fan/turbine blades in case of separation.
The cowling material will probably tear away and the structure underneath will remain circular. I don't think what we see in those pictures contradicts a contact with the runway. Anyway the final report will tell us the truth.
The angle of those marks at the trailing edge of both engine cold stream ducts would indicate that not only half of the engine exhaust cones should be missing/ground away, BUT half of the rear fuselage as well !!! IMHO.
the black marks on the side towards the rear of the cowlings have not necessarily contacted the tarmac itself. That could be sooting from the heat or oil stain.



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Old 23rd May 2020, 14:28
  #254 (permalink)  
 
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Originally Posted by gearlever View Post
Not possible IMHO due to landing gear interlock.
Except if they did it during a bounce. Aircraft bounces, gear retracted, there isn't enough thrust to allow the aircraft to climb away and avoid a second bounce (crash?) without the gear.
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Old 23rd May 2020, 14:29
  #255 (permalink)  
 
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The one thing I am really struggling with is whether they were 3500 feet 5 miles from touchdown - I just cannot see how anyone would continue an approach- crew incapacitation ( they certainly lacked capacity but couldthere be a reason)
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Old 23rd May 2020, 14:29
  #256 (permalink)  
 
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Originally Posted by Capt Quentin McHale View Post
My 2 cents worth people,

Looking at those marks on the engines, there is no way those marks are due to contact with the runway/ground. If there was contact, there would be some rather large obvious flat spots under those engines. The angle of those marks at the trailing edge of both engine cold stream ducts would indicate that not only half of the engine exhaust cones should be missing/ground away, BUT half of the rear fuselage as well !!! IMHO.

Lets leave it to the expert investigators.

Rgds McHale.
You can't just project the angle of those marks rearward. First, you cant distinguish oil/smoke marks from scrape marks, and second, if it scraped, the nacelles and struts would flex upward significantly resulting in the trailing edge areas having more damage than one might expect if they imagine the airplane as being perfectly rigid.
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Old 23rd May 2020, 14:33
  #257 (permalink)  
 
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Originally Posted by krismiler View Post
Also possible that the gear was retracted before the flaps during the go-around. Standard procedure is “Go Around - FLAPS, retract one stage, positive climb - GEAR UP.

Perhaps it happened out of sequence by mistake, “Go Around” and the wheels went up first instead of the flaps.
In my opinion this is the most possible scenerio, but it can't answer why the landing gear doors are intact.

As a general technique to intercept glide slope from above, pilots would early lower the landing gear to increase drag to reduce speed when in high descent rate. So except the TOO LOW GEAR warning, over speed warning will remind pilots to lower the gears, too. It's less possible the pilots FORGET to make the gear down.
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Old 23rd May 2020, 14:34
  #258 (permalink)  
 
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Originally Posted by harrogate View Post
Why would the ATC suggest a belly landing when the pilot reported both engines lost? There hadn't been any talk of gear issues. Or am I missing something?
Quite! I don't think you're missing anyting.

Something had put the likelyhood of a belly landing so firmly in ATC's mind that they actually included a question about it - most unconventionally - in their response to the g/a. They simply wouldn't say that without some very compelling reason. I can think of no other feasible compelling reason other than that they'd already witnessed one seconds before.
Very clearly there was severe damage to both nacelles but no sign of u/c deployed - there's only one way that can happen, ground contact with gear retracted.

The speculation on sink after go-around is called and gear prematurely retracted (perhaps mistakenly instead of flap) sounds by far the most feasible way to circumvent all the warnings - a severe impact on both pods disabling the generators and quite possibly hydraulics and even oil system (my 320 tech is largely forgotten now - perhaps the entire accessory drive system?) which could accont for the rapid loss of both engines. It would be relatively easy and quite credible to severely mishandle a g/a at the end of a high-anxiety unstable approach.

Why fly away from such an event? With TOGA or someting like it already applied, the pucker factor has PF instinctively pulling back on his stick as contact is made and they are flying again. After so much confusion in the preceeding couple of minutes it would surprise me if a crew in that situaton would have the capacity to close the thrust levers and reland, it would only take a couple of seconds of freeze, if that, and they're 15' nose up climbing fast and utterly committed to the g/a. They may not even have had room to reject from there but one suspects that level of cognition may not have been present.

But why no flap deployed in the photos though? Did they get high enough to retract them?
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Old 23rd May 2020, 14:39
  #259 (permalink)  
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It's a strange fuzz, but this explains a lot to an oldtimer that's used to metal.
and the cowls are carbon composite...
I wonder if the entire pod rotated/distorted jet pipe down just a tad as the front's impacted.

I was aware of the possibility of pod strikes before coming on this site. The BBC news had given some clue or another. For me it seems the best bet now the fuzzy surface might be explained.
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Old 23rd May 2020, 14:46
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Originally Posted by henra View Post
May I remind you of these words once the final report is out?

Those cowlings are only thin covers. Underneath is the massive structure designed to contain fan/turbine blades in case of separation.
The cowling material will probably tear away and the structure underneath will remain circular. I don't think what we see in those pictures contradicts a contact with the runway. Anyway the final report will tell us the truth.

the black marks on the side towards the rear of the cowlings have not necessarily contacted the tarmac itself. That could be sooting from the heat or oil stain.

The structure at the bottom of the engine isn't "massive" relative to the weight and speed of the airplane. The transfer gearbox and the low end of the accessory gearbox are at or very near the bottom center line. The cowls are light weight structure not sized to support the airplane without damage. If you scrape the engines significantly you are likely to put holes in the accessory and transfer gearboxes, and will very quickly lose the engine oil. Bearing failure will then follow quickly if high power is commanded.

The regulatory requirements are for such an event are intended simply to not breach the fuel system for crash safety reasons (see 14 CFR 25.994).

Sec. 25.994

Fuel system components.

Fuel system components in an engine nacelle or in the fuselage must be protected from damage that could result in spillage of enough fuel to constitute a fire hazard as a result of a wheels-up landing on a paved runway under each of the conditions prescribed in § 25.721(b).

The requirements and design intent have never been to maintain ability to continue running the engine at high power following such a scrape event. They are simply intended to prevent post-crash fire in a wheels up controlled landing.
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