[V.Narayan]

RIP the 100+ who lost their lives.

I'll wait till the black box and cockpit voice recorder readings are out. At first sight this seems to be a case where either these two pilots will be hailed as heroes or complete incompetent morons.

To the question of the engines failing because they were lying idle for several weeks --- there are very clear and simple maintenance procedures when an aircraft is laid up for some reason. It happens often enough. When an aircraft docks for a lengthy check that might last 4 weeks, the engines are idle too.

The bottom part of the CFM turbofan as fitted to A320s contains the gearbox that drives all the accessories including IIRC {pardon me but I am talking from memory only which isn't always reliable.} the fuel system. No surprise then that with that damage on both engines they dried up seconds later.

Forgetting about landing gears, tragically, seems to be getting fashionable in the Sub-continent. We had flight AI676 less than 3 years ago!

[MegaWhat]

Extremely sad event. I hope the families find the strength to live with this tragedy.

Originally Posted by V.Narayan

The bottom part of the CFM turbofan as fitted to A320s contains the gearbox that drives all the accessories including IIRC {pardon me but I am talking from memory only which isn't always reliable.} the fuel system.

I think so too. The accessory gearbox is towards the bottom. But then I thought aircraft tend to have a fall back option as well. Aren't there batteries to keep the fuel lines active in case of an engine shut down?
Besides, A320s have an option of CFM56 or the IAE V2500. I'm not sure which one PIA uses.

In any case, it's best to wait for more details and an official communication to come out.

[TSIboy]

Originally Posted by V.Narayan

The bottom part of the CFM turbofan as fitted to A320s contains the gearbox that drives all the accessories including IIRC {pardon me but I am talking from memory only which isn't always reliable.} the fuel system. No surprise then that with that damage on both engines they dried up seconds later.

Originally Posted by MegaWhat

I think so too. The accessory gearbox is towards the bottom. But then I thought aircraft tend to have a fall back option as well. Aren't there batteries to keep the fuel lines active in case of an engine shut down?

It is at the bottom of the engine (CFM56) but it’s not just about the fuel lines. The accessory gearbox is a crucial part of the engine, on the lines of a timing belt in our cars. It only takes a bit of damage to upset the whole cycle & set off a catastrophic chain of events.

This damage must’ve happened when the aircraft touched the runway. The pilots then begins to initiate the ‘go-around’ where we would use TOGA power which is the maximum power setting. Now TOGA power wears out an engine hence cannot be used for more than 5 minutes (or 10 minutes one engine inoperative).

An unstablised approach & the human factors associated with it, the mystery of the retracted landing gear, a damaged engine component + TOGA power all added up one after the other, turning out to be fatal for flight 8303. IMO, pilot error would have been the final nail in this case.

Aviation is a very safe mode of transport because for an accident like this to happen, it takes a combination of multiple factors, each happening in a particular sequence. It’s called the Swiss cheese theory.

The CVR and flight data recorders have been recovered and we know what went wrong soon enough. Condolences to the family of the passengers & crew. All it takes is a few seconds for everything to change. Rest In Peace all departed souls

[fhdowntheline]

Here is a further update to the accident from the same source that I posted earlier as initial analysis. He is in fact, talking about damage to the accessory gearbox of the CFM-56 engines.

https://www.youtube.com/watch?v=EFhGnCOtcc8

[V.Narayan]

Originally Posted by fhdowntheline

Here is a further update to the accident from the same source that I posted earlier as initial analysis. He is in fact, talking about damage to the accessory gearbox of the CFM-56 engines.

Thank you for posting this excellent video. The author has explained it very well and exactly as I suspected. Just for clarity of our readers the correct position of the accessories gearbox on this version of the CFM fitted on A320s {as opposed to versions fitted on the B737} is as shown at ~9:38 ie at around the 6 o'clock /7 o'çlock position. The diagramme being used at ~4:10 is of the B737 variant where this gear box is at the 8 o'çlock position. Minor point but just sharing so you can better appreciate the damage it must have suffered from that scrapping.

[fhdowntheline]

https://www.youtube.com/watch?v=URdWBYRtJnY&t=375s

Report from Geo TV also points out that the plane indeed scraped the runway and there are skid marks on the runway. There is also an interesting point about why there was no observation from the Tower, as the plane seemed to be in contact only with KHI Approach team. Also it was higher than normal on the first approach.

[Jeroen]

I picked up this little graph from PPRuNE:

https://www.pprune.org/rumours-news/...l#post10791550



Red line is altitude and the blue bars is the (calculated) rate of descent.

What is very obvious is at least two things:

Obviously the plane did do a go around, but it also shows that it was most likely descending rapidly to capture the glide slope at what was already quite a rapid descent to start with. (not sure if the terrain is partly due to the rapid descent from 10000 -> 2000 ft.)

The various other video’s and ATC recording all seem to suggest these guys were way too high from early on.

There might have been reasons for them doing so, but in general this would be considered a so called unstable approach. Which means you just go around and try again. (unless of course, you are low of fuel or some other emergency).

Anyway, as they have recovered the black boxes some more actual information is likely to surface soon.

[RahuKetu]

What I can make out from the various photographs & videos is that the plane landed without opening of landing gears and scraped it's both engines. Somehow pilots were able to make the aircraft airborne for some time and were trying to land in second attempt. But since both engines were already damaged, they lost altitude very quickly and couldn't reach the runway, thus crashing nearly 1.2 km off the runway in a crowded neighborhood.

[Leoshashi]

A Nice analysis by an Indian Pilot:

https://www.youtube.com/watch?v=bM9ZrliDkNA

[Raghuwire]

Originally Posted by Leoshashi

A Nice analysis by an Indian Pilot:

Superb analysis. It is chilling to hear the communication in the end between ATC and flight! I felt a pang of anxiety, gloom hitting me in the end, thinking of the desperation of the crew.

[fhdowntheline]

Originally Posted by Leoshashi

A Nice analysis by an Indian Pilot:

I think how the accident happened is now beyond much doubt. The pertinent questions are, how did they get into the situation in the first place. Why did they not stick to the planned descent profile ? What were they distracted by? Some of these may never be made public, depending on the situation revealed in the CVR/DFD.

[AlphaKilo]

Originally Posted by Leoshashi

A Nice analysis by an Indian Pilot:

Sorry, riddled with mistakes like @14:55 when he marks the runway, the runway pointing should be between the 180 and 270 and not between 270 and 360.

[Leoshashi]

Originally Posted by AlphaKilo

Sorry, riddled with mistakes like @14:55 when he marks the runway, the runway pointing should be between the 180 and 270 and not between 270 and 360.

True. Did confuse me as well since 25L nomenclature means 250 degrees if I'm not wrong. But I'll ignore that as a minor error, when rest of the analysis is great.

[balenoed_]

That video is one superb analysis, cannot explain in a simpler way than that.

But no information on what happened during the first approach. Was the landing gear not retracted, either forgotten or malfunction? and that made the engine to scrape the tarmac. And subsequent go around and crash.

[Leoshashi]

Originally Posted by balenoed_

That video is one superb analysis, cannot explain in a simpler way than that.

But no information on what happened during the first approach. Was the landing gear not retracted, either forgotten or malfunction? and that made the engine to scrape the tarmac. And subsequent go around and crash.

In case of malfunction, I believe there is another mechanism of lowering it by gravity.

https://youtu.be/o0hr_qjJ9Go

Anyways since not much is known about the first approach, we should wait for the investigation to be over before coming to a conclusion.

Regards,
Shashi