A320 down in Pakistan

[anonymous-user]

Given the aircraft is FBW, could it simply refuse to decend below 200 ft AGL if the gear isn't physically down?

(Obs there would need to be a bypass for extremely rare intentional gear-up belly landings)

[MarkwG]

Munter said:

I think this might be avoiding something unexpected happeneing.

You only want the gear to lower, when you move the leaver. Not when the airspeed drops and you've forgotten the leaver in the "wrong" position.

So either it happens when you operate the control. Or it doesn't happen. In order to avoid an unexpected event in a different scenario.

I agree: better not to come down, than come down at a worse moment. As I understand it, (caveat as always, early days, not an investigator etc): there seems to be a school of thought saying that had they left it on the ground once down, it wouldn't have been pretty but "more" survivable. Hence, bizarre as it perhaps seems, the wheels not coming down in that scenario may be safer, provided you leave the thing there, & don't try & fly it again. I suspect they were so overloaded they hadn't appreciated the gear wasn't down though, & thought they'd made a heavy touch & go. Once you're wrenched it back into the sky...you're a test pilot, basically, no one really knows how it'll behave next.

[aeropilot]

MarkwG said:

I suspect they were so overloaded they hadn't appreciated the gear wasn't down though, & thought they'd made a heavy touch & go.

I would think that's a very plausible scenario.

[Mabbs9]

I agree with the above posters. So much was going wrong they will have had a very noisy flight deck. They appeared to have had no capacity to deal with all of their (possibly) self inflicted problems.

I understand the exasperation expressed with the warning, selection and indication systems. Please be assured they're comprehensive with a great many ways of telling if the gear is down.

The LGCIU is a Landing Gear Control Interface Unit. We have 2 and they're complex and connect with heaps of the other systems to help us out (and occasionally screw things up when they fail). But these guys appeared so far from standard ops that none of this could save them.

Obviously subject to learning more of the facts.

[Krikkit]

Max_Torque said:

Given the aircraft is FBW, could it simply refuse to decend below 200 ft AGL if the gear isn't physically down?

(Obs there would need to be a bypass for extremely rare intentional gear-up belly landings)

Entirely possible you could engineer that in. I suppose it's one of those scenarios that isn't considered necessary until it happens.

It sounds like they were flying pretty stupidly in that rapid a descent, presumably they were simply overloaded by messages from the ECAM/GPWS as they did so and lost track of what was going on. That's contributed to quite a few crashes in the past - bombarding the pilots with warnings doesn't always help.

[Mortgage_tom]

The 220kts at the runway and the decent in the graph.

How far away is both that speed and the angle of decent from an average approach?

Any comparison graph or pilot explain the average approach, e.g. level off at 500 ft and 200 kts..then descend to 0ft and 100kts gradually?


Because Im getting the impression that their approach is so abnormal, that I there must have been an issue forcing them to land as quickly as possible?

Edited by Mortgage_tom on Tuesday 26th May 14:39

[Eric Mc]

Mortgage_tom said:

Because Im getting the impression that their approach is so abnormal, that I there must have been an issue forcing them to land as quickly as possible?

Edited by Mortgage_tom on Tuesday 26th May 14:39

Incompetence?

[J4CKO]

Krikkit said:

Max_Torque said:

Given the aircraft is FBW, could it simply refuse to decend below 200 ft AGL if the gear isn't physically down?

(Obs there would need to be a bypass for extremely rare intentional gear-up belly landings)

Entirely possible you could engineer that in. I suppose it's one of those scenarios that isn't considered necessary until it happens.

It sounds like they were flying pretty stupidly in that rapid a descent, presumably they were simply overloaded by messages from the ECAM/GPWS as they did so and lost track of what was going on. That's contributed to quite a few crashes in the past - bombarding the pilots with warnings doesn't always help.

I think the problem is with engineering stuff like that in is there may be a situation where that is the last thing you want it to do.

[red_slr]

Mortgage_tom said:

The 220kts at the runway and the decent in the graph.

How far away is both that speed and the angle of decent from an average approach?

Any comparison graph or pilot explain the average approach, e.g. level off at 500 ft and 200 kts..then descend to 0ft and 100kts gradually?


Because Im getting the impression that their approach is so abnormal, that I there must have been an issue forcing them to land as quickly as possible?

Edited by Mortgage_tom on Tuesday 26th May 14:39

The problem started at the top of descent.

They just went too late and were behind the curve all the way down. I have not looked at the data but to calc your (rough) TOD then you basically calc the total height to lose, say 30,000ft (for example - runway may not be at sea level) then x by 3 then divide by 1000. So at 30,000ft you want TOD to be c.90nm from the runway.

There is a speed called VREF and they target that VREF speed on approach plus their glide slope. They want to get (slightly) above or exactly on VREF on the glide slope and everything is happy. Most glide slopes are 3-3.5 deg. So fully configured most aircraft are actually under considerable engine power once onto finals and "dirty".

I suspect on this approach they were at idle, trying their best to scrub as much speed as possible whilst getting "sink rate" warnings, probably. We know from the data at times they were getting on for -3500fpm … that's well over twice the normal although well within design limits of the aircraft.

We will have to wait for the full report but its going to be messy.

(edit just to add most jets of this size would be around 140kt on finals plus or minus a few kts)

Edited by red_slr on Tuesday 26th May 15:41

[CrutyRammers]

Munter said:

CrutyRammers said:

Starfighter said:

Your toaster doesn’t take 10 seconds to hold down the lever for it to lock in place. That makes it unnecessary to have audio alarms and voice alarms saying “Toast cold. lever” or 3 red warning light showing the lever was up.

A trivial example, I'll admit I'm just amazed that there's a safety system (overspeed) which prevents the gear dropping, while allowing the lever to be moved - and which then requires manually cycling of the lever in order to try again. Human factors engineering is of interest to me, (largely but not entirely from a software UX perspective which is different, but related), and I always look to the design of aviation controls as an area where they take great care to prevent ambiguity or confusion. I guess my faith is being tested a bit of late.

I think this might be avoiding something unexpected happeneing.

You only want the gear to lower, when you move the leaver. Not when the airspeed drops and you've forgotten the leaver in the "wrong" position.

So either it happens when you operate the control. Or it doesn't happen. In order to avoid an unexpected event in a different scenario.

Yes that would clearly be a problem. I was thinking more of not letting the lever go down if the wheels weren't allowed to go down.
But that of course raises the spectre of, if that interlock fails, you can't put the gear down, so you need an override...
I don't want to derail the thread, I just find this stuff interesting; and I'm sure that all of these avenues have been explored over and again by the guys who design cockpits. On the face of it, it just seems like an obvious potential "hole", but then it may simply be that all the alternatives are worse.

[Mabbs9]

red_slr said:

There is a speed called VREF and they target that VREF speed on approach plus their glide slope. They want to get (slightly) above or exactly on VREF on the glide slope and everything is happy. Most glide slopes are 3-3.5 deg. So fully configured most aircraft are actually under considerable engine power once onto finals and "dirty".)

Edited by red_slr on Tuesday 26th May 15:41

As it happens these 320's will nearly always be at idle even on a 3-3.5 degree slope. They're very slippery and use of speed brake pretty normal just to maintain the speed on approach. The approach they seemed to have attempted was stunningly distant from the norm and impossible to deliver the aircraft to a safe position and speed to land.

[Steve_D]

Krikkit said:

.................That's contributed to quite a few crashes in the past - bombarding the pilots with warnings doesn't always help.

Remember seeing a documentary about data/audio overload of pilots. The chilling (goosebumps etc) bit was a warning in the voice of the pilots daughter saying "Daddy..there's a fire in the engine".

Gets your attention.

Steve

[red_slr]

Mabbs9 said:

red_slr said:

There is a speed called VREF and they target that VREF speed on approach plus their glide slope. They want to get (slightly) above or exactly on VREF on the glide slope and everything is happy. Most glide slopes are 3-3.5 deg. So fully configured most aircraft are actually under considerable engine power once onto finals and "dirty".)

Edited by red_slr on Tuesday 26th May 15:41

As it happens these 320's will nearly always be at idle even on a 3-3.5 degree slope. They're very slippery and use of speed brake pretty normal just to maintain the speed on approach. The approach they seemed to have attempted was stunningly distant from the norm and impossible to deliver the aircraft to a safe position and speed to land.

On finals?

[anonymous-user]

Mabbs9 said:

red_slr said:

There is a speed called VREF and they target that VREF speed on approach plus their glide slope. They want to get (slightly) above or exactly on VREF on the glide slope and everything is happy. Most glide slopes are 3-3.5 deg. So fully configured most aircraft are actually under considerable engine power once onto finals and "dirty".)

Edited by red_slr on Tuesday 26th May 15:41

As it happens these 320's will nearly always be at idle even on a 3-3.5 degree slope. They're very slippery and use of speed brake pretty normal just to maintain the speed on approach. The approach they seemed to have attempted was stunningly distant from the norm and impossible to deliver the aircraft to a safe position and speed to land.

And with the Gear not deployed the L/D would be even better! That alone should have caused them to wonder surely? What is the drag penalty of the gear? affect in AOA vs thrust / flap setting must be significant.

Also explains why the tail didn't touch the R/W when the engines did because they must have been having to actually fly the A/C down on the runway!!! (ie very low AOA/ pitch)

[peter tdci]

red_slr said:

There is a speed called VREF and they target that VREF speed on approach plus their glide slope. They want to get (slightly) above or exactly on VREF on the glide slope and everything is happy. Most glide slopes are 3-3.5 deg. So fully configured most aircraft are actually under considerable engine power once onto finals and "dirty".

I suspect on this approach they were at idle, trying their best to scrub as much speed as possible whilst getting "sink rate" warnings, probably. We know from the data at times they were getting on for -3500fpm … that's well over twice the normal although well within design limits of the aircraft.

We will have to wait for the full report but its going to be messy.

(edit just to add most jets of this size would be around 140kt on finals plus or minus a few kts)

Edited by red_slr on Tuesday 26th May 15:41

In the ATC recording on YouTube, they reported being 'out of 3500' for 3000' established ILS 25L'. On the chart above, their speed at those heights was just below 250kn. The chart also suggests that they descended from 4000' to 2000' in around 30s. Nothing adds up to a stabilised approach or being ILS established with such a rate of descent!

[Starfighter]

red_slr said:

On finals?

Final approach. On the right course and glide slope for the runway and with the aircraft configured to land dirty with flaps, slats and gear extended.

[peter tdci]

Starfighter said:

red_slr said:

On finals?

Final approach. On the right course and glide slope for the runway and with the aircraft configured to land dirty with flaps, slats and gear extended.

I think it was a reply to the poster who said that the engines were typically at (or near) idle thrust on the glideslope, rather than asking what it meant

[Mabbs9]

red_slr said:

On finals?

Yep. I'm an Airbus driver btw. You're not wrong that many airliners have a fair bit of thrust on in the landing configuration. The small Airbus often has a little, depending on headwind. In still air or tailwind it's often idle thrust into the flare.

Edited by Mabbs9 on Tuesday 26th May 19:56

[48k]

So to summerise - the chain of events seems to begin with the crew missing the Top of Descent for some yet-to-be-ascertained reason and trying to recover the situation by descending steeper and faster than normal to intercept the glide slope. Is that about the gist of it?

[MB140]

aeropilot said:

Bandit110 said:

DuraAce said:

Down to the crew to not get into such a situation in the first place. Shocking CRM. The approach should've been binned long before they got to that point in the chain of events.
Nobody else to blame but themselves (going on current/available info)

Yep, I'm with you, based on the info so far

Data is looking like they 'touched down' onto the runway at something like 200-210 knts......

Jesus Christ. We were 139 over the threshold today with 9 knot correction 707 (E3-D).

I doubt even the old Tornado GR1 flapless was 200knts landing speed.

Edited by MB140 on Tuesday 26th May 20:08