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PIA A320 Crash Karachi

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PIA A320 Crash Karachi

Old 1st Jul 2020, 17:56
  #1541 (permalink)  
 
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Originally Posted by gums View Post
My goal was to get over to the tech log and talk about the profile and the gear logic. Someplace it was mentioned that you couldn't lower the gear above "xxx" knots, and I unnerstan that. But then what happens when it's down and you exceed "xxx" knots? Does HAL raise the gear?
That was discussed in this thread a few dozen pages ago, and I think that the consensus was 'no' (and IIRC the rationale was 'it would damage the gear doors if the system did that at speeds in excess of the limits from the manual ...). Go back about a week or two in posts and I think you'll find the discussion on that. Starts at around page 28, something about a logic gate based on IAS of 260 knots.
Simple question, but instead the thread was deleted and over here with armchair aviation afficianodos and a few real pilots/crew we still keep harping on ethnic and cultural crapola. .
I think that part of Clandestino's point was that an unhealthy cockpit gradient can happen anywhere.
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Old 1st Jul 2020, 19:02
  #1542 (permalink)  
 
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Originally Posted by farsouth View Post
The Co pilot three times suggested going around before the captain took control, and landed, gear-up, at 40kts above the flaps up vref, and >60kts above the vref for the selected flap setting.

Both ex-USAF pilots.
And the captain was a former FAA Air Safety Inspector. 'Watch this...'
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Old 2nd Jul 2020, 13:24
  #1543 (permalink)  

Only half a speed-brake
 
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L/G won't come down above certain speed, due to hydraulic being de-powered.

If the wheels are out, and you dive above V(lo), the hydraulics will at best cut off again. No autoretract fitted, let alone a gravity one. 😊
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Old 2nd Jul 2020, 13:53
  #1544 (permalink)  
 
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Auto retraction simply not possible and even the concept is illogical. VLE is 280kt. retraction speed is 220kts. If it doesn't allow you to lower beyond 260kt. why will it retract?
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Old 2nd Jul 2020, 14:35
  #1545 (permalink)  
 
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Good point(s), Vilas.

My concern was that HAL may have retracted the gear on the initial approach attempt with no pilot action. e.g. they had gear down but then speeded up above "xxx" knots. I don't know of any plane that lets HAL retract the gear without a pilot command, but there some that do not send the gear handle signals to the hydraulics without a signal from the WoW switch, huh? Sorry I have not seen all the plots of data from the FDR, and lost the FCOM I had downloaded back in 447 days.

I still would still like to see this discussion on the Tech Log and let the management and other stuff stay here.

Last edited by gums; 2nd Jul 2020 at 14:37. Reason: tech clarification
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Old 2nd Jul 2020, 16:12
  #1546 (permalink)  

Only half a speed-brake
 
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Vilas, we're saying the same thing.

gums, the A320 is a very conventional design, no HAL. Although the FBW has hard limits at the envelope's edges.

The raising of the gear and retraction of speed-brakes at 5 NM on the first approach, is consistent with crew wanting to put the gear down but not realizing it already was. So the handle was just moved the other way.
The G/A gear flick DN and UP identically so.

It has happened before (*). If it was not for the overspeed clacker, they would hear and see the ECAM warning. If it was not for the high speed, the GPWS would have told them as well.

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Old 2nd Jul 2020, 17:07
  #1547 (permalink)  
 
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This was an approach like no other, but it must have been carried out that way for some reason. No matter how pointless it appears to have been, it was not pointless to the pilot. Or the first officer so it seems.
There has been much discussion on this forum about the gear, and what would happen in the case of overspeed and gear selection.
If you were not sure what the gear would do, you could try cycling it at high speed. With a long enough runway and a compliant copilot, why not try it and see what happens? Why not indeed.
This accident makes no sense whatsoever except for this. If an attempt was being made to settle an argument regarding gear selection and overspeed limits, it is not so strange at all.

Last edited by ferry pilot; 2nd Jul 2020 at 18:00.
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Old 2nd Jul 2020, 17:20
  #1548 (permalink)  
 
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Sorry, Detent, but that dog won't hunt.

the A320 is a very conventional design, no HAL. Although the FBW has hard limits at the envelope's edges.
I am more familiar with the 330 due to the 447 discussions some years back, but your FBW has a lot more modes and submodes and "shaping" algorithms of control surface movement and rates than so-called "protection" at the edges of the envelope. e.g. bank angle and other limits vary according to which "alternate:" law you are in until "direct".

The raising of the gear and retraction of speed-brakes at 5 NM on the first approach, is consistent with crew wanting to put the gear down but not realizing it already was. So the handle was just moved the other way.The G/A gear flick DN and UP identically so.
My diagrams of the instrument panel seem to show a handle and adjacent indicator just above the center pedestal. Clearly marked "up" and "down". So your last minute checks don't involve touching or visually verifying the position and the lights?

If it was not for the high speed, the GPWS would have told them as well.
I thot HAL knew if gear was down for a landing and the FBW was switching into the "flare" mode at "x" altitude above the ground/runway. So can I perform CFIT by just getting above "x" speed with gear up? Somehow, I thot GPWS/HAL would have said something. "Dave? Sure you wanna try this?" I gotta admit they "greased it on", but maybe that was because they were not in "flare" mode, which seems to be almost pure "direct" law with "heavier" pitch command deflection.

Oh well, back to the Tech Log.....
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Old 2nd Jul 2020, 18:15
  #1549 (permalink)  
 
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Originally Posted by ferry pilot View Post
There has been much discussion on this forum about the gear, and what would happen in the case of overspeed and gear selection.
From the report it seems they hit a maximum of 258kts IAS at 2000ft just before the indicated retraction of L/G. In which case the 260kts overspeed limit should not become an issue, so far as L/G is concerned.

That aside, I am curious about a small difference in the report concerning the landing gear controls.

The report at 7221ft determines that the FDR "indicated action of lowering of the landing gears".

At 1740ft the FDR "shows action of raising of the landing gears" and "the landing gears and speed brakes were retracted".

Does it mean that between 7221ft and 1740ft we cannot tell from the FDR evidence whether the L/G was actually extended, even if there is evidence to show that action was taken to lower it?

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Old 2nd Jul 2020, 19:05
  #1550 (permalink)  
 
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Gums, if you go back 20 or 40 pages () there is a discussion about the gear up warning. Apparently, above 210 knots, the warning changes from 'Too Low Gear' to the GPWS 'Too Low Terrain' (or words to that affect) based on the assumption that if your going over 210 knots, you're probably not trying to land. Assuming they got the 'Too Low Terrain' warning, it would be somewhat understandable if the pilots dismissed it as a nuisance since they thought they were landing.
I presume similar flight control logic would have come into play (or not come into play) since the gear was up and they were going to fast.
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Old 2nd Jul 2020, 19:28
  #1551 (permalink)  
 
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Yeah, TD I finally found an A320 FCOM and am wading thru it. Definitely looks like the "Too Low Terrain" warning should have come on, and I agree that it could be judged a nuisance if you trying to land and already know you are faster than normal.
'
Trying to find the excruciating details for the "flare" mode, as I am thinking it was not in effect and normal gear up control laws helped them to grease it on. Might also explain why thrust reversers may not have actually deployed regardless of throttle position/selection/whatever when WoW shows airborne.
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Old 2nd Jul 2020, 20:29
  #1552 (permalink)  
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Originally Posted by farsouth View Post
Here’s a link to the report on the accident referred to above. A lot of similarities, and certainly shows that the PIA accident cannot only be blamed on a non-“Western cultural” mindset.
Farsouth, it is quite possible that the PIA can in fact be blamed on a non-western mindset while at the same time the Houston accident can be blamed on an excessively western mindset (ie cowboy).

Your point that western aviation mindset isn’t infallible is of course correct.
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Old 2nd Jul 2020, 22:27
  #1553 (permalink)  
 
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Another factor I have not seen mentioned is the disconnection of the autopilot early in the approach @ about 9000’. .

A320 gets full speed brake without AP but only half with.

This is consistent with recognition that we are high and we’re going to get down as fast as we can. Further backed up by the 7000{‘ lowering of the gear.
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Old 2nd Jul 2020, 23:40
  #1554 (permalink)  

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Originally Posted by gums View Post
I am more familiar with the 330 due to the 447 discussions some years back, but your FBW has a lot more modes and submodes
True, though rated pilots might find your re-phrasing a bit coarse around the edges. The gear v.s. HAL was what I was pointing at, meaning to say apart from the F/CTL FWB, the A320 is a totally conventional aircraft. Vilas pointed the rest.

For your Q about verifying lights and levers for the final checks: Yes we do, and other pilots too. Typically challenge-response read from a laminated check-list, confirmed by both pairs of eyes.

Unlike the doomed crew. Come to think of it, once they already raised the L/G thinking they were lowering it, touching the lever would not amount to much. The lights would be showing nothin, with gear up and closed. ... why no "3 greens check"??? Well, easy. Normally the ECAM upper screen displays abbreviated "LDG MEMO" with 5 action lines, that change as you finish the individual items (arm spoilers, LG/DN). Hence we verify (from the paper C/L) "ECAM MEMO? .... (displayed) LANDING: (showing) NO-BLUE" I.e. we look at the ECAM for LANDING memo, that is showing all green text with no blue action items left.

The memo comes up automatically whenever RA<2500 ft (large A/C passing below you in cruise, you will get it at 35k - like I said, no HAL apart from the F/CTL). The problem for the PIA flight is that the LDG MEMO occupies the same ECAM screen space on the upper display unit (called Engine/Warning Display) as any ABN warning will and those take precedence. Hence in overspeed it shows OVERSPEED in red letters and the applicable limiting speed, and no LDG memo.

There are 3 green triangles showing on the panel above the gear lever, but those we do not really check actively, it's done via the ECAM LDG MEMO. For normal landing, the lower DU shows ECAM "WHEEL page" with another 3+3 green triangles, ... the page automatically comes on with ... you guessed right: selecting the L/G down. Malakia.

Basically, if you attempt to land this aeroplane in flap overspeed and ignore the landing paper check-list (which even lists the 5 action lines in print, in case the screen went T.U.), it is perfectly possible to land gear up unnoticed, unless you notice.
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Old 3rd Jul 2020, 03:30
  #1555 (permalink)  
 
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Thanks for the info, Detent.

Quite a bit different with electronic "help" for the procedures and such from what I endured for a few thousand hours.


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Old 3rd Jul 2020, 04:41
  #1556 (permalink)  
 
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At which point does a person lose faith in the electronics, assume that all the various warning signals are false, and maybe remark that there must be technical problems?
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Old 3rd Jul 2020, 04:43
  #1557 (permalink)  
 
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Originally Posted by gums
Trying to find the excruciating details for the "flare" mode, as I am thinking it was not in effect and normal gear up control laws helped them to grease it on
You can 'grease' it on with Flare Mode btw!!! HAL as you call it is not all doom and gloom...
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Old 3rd Jul 2020, 06:05
  #1558 (permalink)  
 
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Originally Posted by FlightDetent View Post
There are 3 green triangles showing on the panel above the gear lever, but those we do not really check actively, it's done via the ECAM LDG MEMO. For normal landing, the lower DU shows ECAM "WHEEL page" with another 3+3 green triangles, ... the page automatically comes on with ... you guessed right: selecting the L/G down. Malakia.
I'd considered the lack of presentation of this page ought to have been another hint. Maybe the lower ECAM was otherwise occupied for some reason? Admittedly, this would've been a subtle hint, lost in th ocean of bells and whistles going off.

Good point on the LDG MEMO not showing while above Vmax. The more I think about it, the less sense it makes. They had the GPWS going off, airspeed above Vmax and no LDG MEMO on the ECAM. I hope the final report shows us what the screens looked like at 500ft.

Maybe they had no warnings. Maybe the combination of things warnings that had to be presented was way beyond what the engineers had envisioned, and the DMC's and FWC's just gave up and rebooted.
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Old 3rd Jul 2020, 08:18
  #1559 (permalink)  
 
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Certainly appears to be mental overload, for whatever reason.

We are not supposed to speculate but........a possible scenario is as follows:

Captain is a very autocratic Captain who had marginal ability and got into the LHS by other means.......and a meek or compliant F/O.

The Cap f****d up the descent, but did not want to lose face to his F/O, so instead of acknowledging his mistake and asking for extra track miles, the Cap kept saying he was comfortable, and barked orders to the F/O and then ignored instructions from ATC. I can imagine Cap saying "He [ATC] is a donkey, what does he know, we are on the ILS and visual....".

The A/P disconnect is consistent with wanting full speed brake to increase rate of descent. Selecting gear down is also consistent with this, although a bit desperate when all you need are some more track miles. But pride probably prevented Cap from asking or agreeing to longer vectors.

Cap almost got it sorted, but then, as he just about regained the profile, (but crazy fast), his "muscle memory" kicked in, and he barked "Gear", while stowing the speed brakes, as you would if you had just recovered a slightly high and a fast approach. Unfortunately, the Gear was already selected down but the F/O had stopped thinking for himself or was too cowed to say anything, so simply moved the lever in response to the shouted order, in this case to UP.

Cap, not realising the Gear reversal, now thought he had made it. He ignored all the warnings that must have been sounding and became focussed on the runway and the landing. He forgot speed, forgot stability and forgot landing checklist, one item of which is to check the gear is down. (As others have said ECAM memo might not have been displayed, nor the Wheels page on the SD. However there are secondary independent conventional gear indicator lights on Airbus FBW - 'three greens').

Cap flies down and flares, but because of ridiculous speed, the sink rate is much less than in a normal flare and he greases it on, lower and lower and..........oh sh*t !!...............TOGA!! They get airborne again but having fatally damaged the engines, the subsequent accident is now sadly inevitable. RIP

All possibly caused by ego, and a person not able to say, "Oooops, sorry, I made a mess of that! [descent]. Can you ask for some more track miles". RIP


I have a simple mantra I use at a few miles out from landing to double-check we can land safely: "Fly......By......Wire".

F = Flaps. Are they set for landing?
B = Brakes. Is there any residual pressure and has auto-brake been selected?
W = Wheels. Is the gear down?

As I say each item quietly to myself, I visually check the appropriate indicators in front of me

Last edited by Uplinker; 3rd Jul 2020 at 08:40.
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Old 3rd Jul 2020, 11:01
  #1560 (permalink)  

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Has it ever been made clear if any form of FDM operated prior to the crash?
If it did or didn’t, then hopefully it will be part of the AAIB investigation.

The EASA suspension letter gives some insight as to the short term relationship with PIA.

The LEVEL ONE item ~ SMS shortcomings. That speaks volumes.....
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