Incident: Airbus A330 at Taipei, primary computers failed on touchdown (2020)

https://avherald.com/h?article=4d97ca46&opt=0

by akamaka • 5 years ago

300 133 5 years ago

avherald.com

mplanchard• 5 years ago

This could probably use a 2020 in the title

akamaka• 5 years ago

Final report was just issued this week.

alkonaut• 5 years ago

Maybe explains why there were only 87 pax in a 330 too.

mysterydip• 5 years ago

I don't entirely grok the vocabulary, but it sounds like the computers each said "This input is outside of limits, something must be wrong with me" so shut off for safety. But is there a mechanism that says "we can't all be wrong, it must be the sensor", to avoid situations like this?

noir_lord• 5 years ago

"we can't all be wrong, it must be the sensor", to avoid situations like this?

Not an expert but my understanding is that typically with these systems they take a poll and vote, if 1/3 disagree it's ignored if 2/3 disagree they scream and switch to manual/fallback simpler systems.

zymhan3• 5 years ago

Indeed, it seems like the computers were not in agreement

the combination of a high COM/MON channels asynchronism

In this case, since the automation failed, the plane reverted to "Direct law", where the pilot's inputs directly control the plane, instead of passing through computer checks first.

sgtnoodle• 5 years ago

For a binary signal, it's impossible for all three to mismatch. For a more analog signal, all three will generally mismatch to some extent whether it's in time or in space or both.

Fault tolerance and fault detection are two separate but often coupled concepts. Systems can be designed to be inherently tolerant to a fault without detecting the fault (and good designs often are). All faults need to be detected eventually, though, so that they can be repaired before more faults occur and compound into a broken system.

There's typically very tight timing requirements for fault tolerance, and significantly looser timing requirements for detection. As a result, you can often solve them differently. In a 3 string system with voting, it's often the case that the median signal is used for control without any interpretation of "goodness". That strategy works fine for short time periods of fault tolerance, as two strings would have to produce bad signals for the system to be affected. Separate from the median voting control path, you would then have a variety of consistency checking algorithms looking at the three signals and trying to intelligently determine whether any of the strings have failed. Those algorithms are often stateful and complicated, and rely on heavy filtering to avoid false positives.

When a fault is detected, at minimum it needs to be communicated to an operator. In some cases, the detected fault will also trigger a "fault response", i.e. disabling the offending computer.

In this case, it sounds like maybe a fault detection algorithm had a false positive that disabled the computer, and the same algorithm was running on all three computers.

Despite there being 3 computers, it doesn't sound like this is a 3 string voting system. Rather, each of the three computers are independently able to control the system. The 3 strings exist for redundancy rather than for fault tolerance. Fault tolerance is provided by having two computers that cross-check everything they do, and third computer is there so that the cross-checking is fault tolerant. Two string redundancy is very common in automotive and aerospace.

jstanley• 5 years ago

How can you tell the difference between 1/3 disagreeing and 2/3 disagreeing?

If 2/3 disagree, don't they just agree with each other, and therefore it still only looks like 1/3 disagreeing?

zymhan3• 5 years ago

I'm not sure there was a sensor issue here. It appears that the Flight Computer monitoring routine for the Rudder position somehow caused all three computers to crash. This was somehow exacerbated by the pilot's rudder inputs, which I don't fully understand

the combination of a high COM/MON channels asynchronism and the pilot pedal inputs resulted in the rudder order difference between the two channels to exceed the monitoring threshold

The flight computer failure resulted in the inability to use two braking mechanisms, Thrust Reversers (make air from the engine go forwardsish) and Spoilers (stop the wing from producing lift, putting more weight on the wheels and making the brakes more effective.

salawat3• 5 years ago

The thing that bugs me is "did the pilots engage those systems manually?"

And

How was their reaction time doing so compared to someone who would be used to doing so via muscle memory on the regular?

Automating things is nice and all, but there is something to be said for keeping manual skills sharp.

ak217• 5 years ago

It sounds like it was more complex than that. The computers shut down because of a COM-MON order mismatch. In other words, there is a watchdog in the system that monitors the three computers and their orders (control surface movements, etc. - in this case rudder inputs). There are 3 computers and one of them is designated COM (command) while another is designated MON (monitoring). If the values of the inputs that the computers want to send to the actuators diverge too much for too long, the command computer is disconnected and another computer is designated command. In this case it sounds like the command and monitoring computers had a significant delay between them when they transitioned from flight law (settings used in flight) to ground law (settings used while on the ground) while the pilot was also applying rudder (which is very common during landing, to correct for crosswind). When on the ground, the rudder is set to not deflect as much from the pilot's inputs compared to when in the air. It sounds like normally the computers switch to ground law close enough in time that the resulting mismatch is ignored, but in this case the significant delay caused a "split brain" situation and the watchdog disconnected all 3 computers.

Perhaps the root cause is an issue in the weight-on-wheel sensor inputs that the computers use to transition. The computers need to use redundant sensors so they don't all rely on the same faulty sensor, but maybe the sensors are not appropriately cross-fed or the sensor input combination logic is too different between the computers.

The problem with not disconnecting a computer in this situation is that bad inputs from that computer may also cause a crash. But maybe if no other computer is available to take its place the logic should be different, at least during takeoff/landing.

avianlyric15• 5 years ago

Im gonna re-explain what you’ve written in language I’m more familiar with to check my understanding, and hopefully you can correct any errors I make.

As I understand it the A330 has three primary flight computers, all observing the same inputs (which might come from different physical sensors monitoring the same thing?) and producing outputs, also know as “orders” for other systems in the plan, like actuators.

Of these three computers, one will act as the primary command computer (COM), one as a monitoring computer (MON), the third is spare and normally ignored. Only orders from the COM machine is sent to downstream systems like actuators.

There’s a separate watchdog system that monitors the outputs (orders) of both the COM and MON, and if their order values diverge by too much for too long, it shuts down the COM computer and passes control to the MON computer and the spare. As part of this process one of those two computers becomes COM the other MON. I assume the size of the divergence determines how long they can diverge for. A large divergence is only allowable for a very short period of time, and a small divergence is allowed for longer.

In addition to all of this, the computers have different operating modes which changes how they respond to inputs. In this case the relevant states are “normal law” for in the air, and “ground law” for on the ground. One things that’s different between these states is how tightly coupled rudder inputs from the pilot are to rudder orders to the actuator. In the air the rudder is less tightly coupled than on the ground. E.g. commanding full left rudder in the air results in less physical movement of the rudder than the same command on the ground.

When the plane lands, detected by a pressure sensor in the landing gear, the computers transition from “normal law” to “ground law”. Which for some outputs, like the rudder, might result in a step change in outputs (orders) from the computers.

So in this specific scenario what happened is that the flight computers for some reason didn’t transition between “normal law” and “ground law” simultaneously (or close enough to simultaneously). So the COM computer significantly changed its rudder output as a result of changing law, but the MON computer didn’t, because it hadn’t changed law yet (the inverse of this is also possible). As a result they were producing very large differences in rudder orders, resulting in the monitoring watchdog killing the COM computer and failing over to the spare. Where the above situation happened a second time, resulting in all computers being shut down.

Is all of the above correct?

All of this does make me wonder, if changing law can result in computer outputs quickly changing, doesn’t that make law changes inherently dangerous? If you’re a pilot landing a plane applying significant rudder inputs, doesn’t the above me that those inputs will have a vastly different effect once the wheels touch the runway?

cwizou2• 5 years ago

Perhaps the root cause is an issue in the weight-on-wheel sensor inputs that the computers use to transition. The computers need to use redundant sensors so they don't all rely on the same faulty sensor, but maybe the sensors are not appropriately cross-fed or the sensor input combination logic is too different between the computers.

This would indeed explain the discrepancies between COM/MON which is what they called asynchronicity (which is a bit different from where my mind went when I read that word the first time). There was no particular fault found in the computers.

Maybe wet runway factored in a bit (or some other issue with the runway itself), but this is a common occurence around the world and this was a first on the whole 330/340 family.

The problem with not disconnecting a computer in this situation is that bad inputs from that computer may also cause a crash. But maybe if no other computer is available to take its place the logic should be different, at least during takeoff/landing.

Yes, only thing I would add is that they failed in cascade within one second of each other, 3 seconds after main gear touching (and before the nose gear touched down):

Three seconds after the main gear touched down, autobrake system fault was recorded on FDR. One second later, PRIM1/PRIM2/PRIM3 faults were recorded at the same time and the spoilers retracted, as the ground spoiler function was lost.

Whether all three should be allowed to be failed within one second then default back to direct law (manual) is a hard question to solve, in this precise case it seems like try again would have maybe worked? Would it always be safe to do a retry? I don't know. This is a super critical phase of flight so retrying doesn't sound safe.

Apparently they would have needed 2 functional for full autobrake:

Ground spoilers function requires at least one functional FCPC, arming autobrake requires at least two functional FCPCs, deployment of thrust reversers require unlock signal from either FCPC1 or FCPC3

phkahler• 5 years ago

That's how I read it too. The discrepancy was deemed "I'm broken and need to shut down" instead of something more benign in a condition they didnt realize might happen. That a critical difference since all 3 will think "I'm broken" as happened here.

That stuff can be hard to get right. Glad they found this one with 10 meters to spare.

avianlyric15• 5 years ago

It seems that flight planning is done on the basis that the loss of all flight computers is possible, and to make sure that your runway is long enough to accommodate that situation.

So thankfully the loss of all three computers isn’t inherently dangerous, and is demonstrated by this incident. Based on my reading of the report the primary take away from this (apart from a an issue with the flight computers software), is that flight plans aren’t and prep by the airport wasn’t conservative enough, so they ended up with slightly less safety margin than they expected in this scenario.

the_duke• 5 years ago

Odd that there is no information from Airbus there.

FYI: the comment section contains some interesting background.

zymhan3• 5 years ago

Well there is a single bullet point from/about Airbus

7. Following the occurrence, Airbus reviewed its in-service experience, and confirmed that no other triple PRIM fault at touchdown event had been reported on A330/A340 aircraft family since entry into service. The A330/A340 fleet fitted with electrical rudder has accumulated 8.7 millions of Flight Cycles and 44.3 millions of Flight Hours (in-service data from April 2020).

thomasjudge• 5 years ago

So, does this mean that the outcome was, Airbus reviewed the situation and the data, and made no changes or corrections to the system?

ceejayoz• 5 years ago

The crew applied maximum manual braking and managed to stop the aircraft 10 meters/33 feet ahead of the runway end (runway length 2600 meters/8530 feet).

Hope the crew had their brown pants on.

encoderer• 5 years ago

From the cockpit, 33’ must have looked right under their nose.

futhey• 5 years ago

Songshan's not a large airport, it's mostly used for domestic flights, and a few nearby international destinations. Single runway, immediate obstacles on both ends (no matter which way you land). Although, runway 10 is eastbound & it's just a fence and small parking lot, minor traffic, and then you land in the river.

Sounds like it would have been stressful.

rzzzt• 5 years ago

Why can't thrust reversers and spoilers be engaged without computer supervision? The article just says that ground spoilers require one of the three flight computers to remain operative, autobrake needs two, reversers needs one out of two specific units to be running to unlock.

bdonlan• 5 years ago

All flight controls on the A330 are fly-by-wire - they're connected via computers. The most critical surfaces have secondary, dumb controllers that can take over if the primary flight computers fail, but less critical systems may not be connected to those backup systems - it's expected that a triple fault of the primary flight computers should be very rare, and manual braking is available as a backup after all.

NovemberWhiskey• 5 years ago

Right. In this case we have a completely-unprecedented triple failure of the primary flight control system causing loss of auto-brake, spoilers and thrust reversers; a wet runway with less than expected braking action; a tailwind landing and still a happy outcome.

Honestly defense-in-depth seems to be working OK here.

jeffbee• 5 years ago

Accidental deployment of thrust reversers is a bad thing and incidents of that kind have killed a lot of people. It seems better to bias the failure modes toward non-deployment. The reversers are not critical systems, and aircraft are permitted to operate even if their reversers are not operational. They mainly save wear and tear on the tires and brakes.

braza• 5 years ago

This was one of the reasons of why TAM3057 crashed in São Paulo.

HPsquared• 5 years ago

In other words, it's more important to ensure they don't deploy when they shouldn't, than that they do deploy when requested.

avianlyric15• 5 years ago

Based on the article it seems this is a safety feature to prevent the accidental activation of those functions in flight.

I imagine there’s zero reasons for using ground spoilers or reverse thrusters in the air, and doing so would probably cause a complete loss of aircraft.

So to make sure that can’t happen, the functions require a positive “it’s safe to active now” signal from the flight computers.

So the functions themselves are quite capable of operating without the flight computers. They simply refuse to do so unless a flight computer has given them the all clear.

numpad0• 5 years ago

Japan Airlines Flight 350 accident in 1982 - at 164ft/50m AGL, the captain suffering a schizophrenic attack disengaged A/P, activated reversers, and pushed down his control column hard forward. 24 deaths, 150 survivors.

ugh.

EdwardDiego• 5 years ago

I imagine there’s zero reasons for using ground spoilers or reverse thrusters in the air, and doing so would probably cause a complete loss of aircraft.

It has, on several occasions, although I'm not aware of any where it was a commanded deployment of reversers in flight.

https://en.wikipedia.org/wiki/Lauda_Air_Flight_004 https://en.wikipedia.org/wiki/TAM_Transportes_Aéreos_Regiona...

polishdude20• 5 years ago

Actually the ground spoilers can be used in a spectrum during flight especially when the plane is descending and needs to slow down as well.

sinuhe69• 5 years ago

Remind me of the Ariane 5 maiden flight: redundant hardwares does not protect against unsanitized inputs. I don't know much about the design of the airbuses, but I think it's sensible to specify the last primary computer running in a different mode as the first two, simply because double hardware failure is very very unlikely. So it boils down to either software bug and or unsanitized inputs. Assuming that, the last computer should provide some basic but safe functions.

strictfp• 5 years ago

I've seen bad user input, one very unusual char, bring down a whole self-healing geographically redundant cluster of machines running an expensive commercial cluster software. Any connected devices can bring each other down.

andrewnicolalde• 5 years ago

That sounds like a great war story if you’re open to telling it :)

salawat3• 5 years ago

Story, story, story, story!

avianlyric15• 5 years ago

Well that’s kind of what happened. The primary flight computers all failed, to the plane fell back to “direct law”, which means pilot input is directly transmitted to control systems without a computer attempting to interpret intent or protect against pilot error.

As a consequence a lot of the more advanced functions became disabled because they rely on the primary flight computer to indicate when it’s safe for them to operate. Presumably because accidental operation of those features in flight is extremely dangerous.

oakmad4• 5 years ago

For everyone commenting about different hardware failure modes and possible solutions. Take a look at the airbus « flight control laws » such as https://apstraining.com/wp-content/uploads/FCS-Airbus-Quick-... it governs what happens to flight controls and what protections are available in different scenarios. In this case the system worked, it crashed and reverted to direct law providing manual braking control.

Off topic but I found this very interesting « The deceleration performance of the occurrence flight between 6,600 feet and 7,300 feet from the threshold of runway 10 deteriorated. It may be due to paint marking and rubber deposit on the touchdown zone of runway 28. »

cwizou2• 5 years ago

The deceleration performance of the occurrence flight between 6,600 feet and 7,300 feet from the threshold of runway 10 deteriorated. It may be due to paint marking and rubber deposit on the touchdown zone of runway 28

Just to clarify for others, this is the same runway but taken in two different directions (west to east and east to west, multiply the number by 10 and you get [rounded] angle in degree, so 100ish vs 280ish). It's 8500 ft. long and it looks like there was a loss of performance around the "touchdown" point of going the other way on that runway, where you had accumulated rubber from those landings (which is pretty normal and monitored, as pointed by leecb below), if that makes any sense.

leecb• 5 years ago

accumulated rubber from those landings

Rubber accumulation on runways is a normal and expected situation. Part of runway maintenance at airports serving larger aircraft includes regular removal of the rubber using high pressure water or chemicals.

https://en.wikipedia.org/wiki/Airfield_rubber_removal

oakmad4• 5 years ago

Its unfortunate they don’t calculate how big a difference it made. They’d calculated a 170ft margin and stopped with 30ft margin and I’m curious what their braking delta was for that 700ft of deterioration.

« With three FCPCs inoperative, actual remaining runway distance (30 feet margin) of the occurrence flight was shorter than the calculated value (172 feet margin), possibly due to tailwinds, runway conditions, and manual braking as these factors might increase the braking distance. »

I get sucked into how all the little things that are not right make such a big difference in these kind of scenarios.

jcrawfordor• 5 years ago

Build-up of rubber from the tires of landing airplanes is a routine problem with runway maintenance. Typically the airport authority will use a friction-measurement device at regular intervals to determine when the surface friction of the runway has fallen below required parameters, and resurface. But rain makes things much worse and might have combined with rubber build-up to produce a particularly slick section.

Flying light aircraft, I was taught to avoid landing right in the touchdown zone just to have better traction. I'm not sure if this is actually useful or just Old Pilot Superstition but it has some logic to it, and putting a Skyhawk down on a 14k foot runway you have a lot of room for eccentric opinions (similar to landing just a touch off centerline so the nosewheel isn't on the painted stripes, another one I've heard people mention as a "best bad practice").

rteuionwiv• 5 years ago

I don't think anything too bad could happen when landing light aircraft on slippery but long runway. I was doing some winter flying and was landing pa28 on slippery runway (compressed snow) and I didn't noticed any difference until i started pressing brakes which had virtually no effect on deceleration. On touchdown you have a lot of aerodynamic authority on your controls so runway friction doesn't really matter unless you have super strong crosswind that could blow you out the runway i guess.

azalemeth2• 5 years ago

My dad was a commercial pilot, and taught me to fly at a young age. One of the bits of sage advice was something along the lines of "if your nosegear has two or more wheels, try to get it bang on the centre line, every time. Otherwise, miss a little tiny bit. The lights go THUMP-THUMP-THUMP and eventually drive you mad or, combined with a little gust of wind, cause you to hop once more".

I think there's a lot of Old Pilot Superstition with more than a dollop of truth in it.

kylegordon• 5 years ago

If I recall rightly Concorde pilots often took control from autoland and landed it slightly off the center line.

This was to avoid upsetting the passengers and to ensure the champagne didn't get shaken too much.

ErikVandeWater2• 5 years ago

It's very odd they don't do anything to speed up the wheels or apply a coating of water to them on dry days to avoid extreme wear and excess rubber for future planes landing.

Even a passive design with the shape of the tread could help substantially reduce the amount of rubber scraped off the wheel on each landing.

teeray• 5 years ago

I wonder what would have happened if they tried to go around? The TO/GA is configured ahead of time in the FMS… so if the flight computers are out, I wonder if there’s some hard-coded performance targets for the engines in a go around situation.

concerned_user• 5 years ago

They would push throttle manually in max power and perform the maneuver by hand.

hugh-avherald• 5 years ago

There was barely a second between the first indication of a primary computer fault and the call for reversers to deploy. Once you select reverse thrust, you cannot go around under any circumstances.

strogonoff2• 5 years ago

It’s an interesting scenario. Your wheels touch the ground; you engage reverse thrust and it instantly fails; you are rolling at dangerous landing speed but now can’t go around?

Relatedly, I wonder why did the pilots not engage the regular brakes ASAP.

bryan0• 5 years ago

The 2020 should be removed from the title. The article is mostly new information from the final report:

On Sep 3rd 2021 Taiwan's ASC released their final report in Chinese and their English Executive Summary concluding the probable causes of the incident were: …

FatalLogic2• 5 years ago

The flight data recorder chart on page 114 of the Chinese-language report[0] seems to record that the pilots hit the brakes very hard in the last few seconds, maybe when they realized they were close to overrunning the runway.

That caused a sudden peak of -0.47g deceleration, so it looks as if they could have used the brakes to slow the plane earlier on the runway, but maybe they didn't because they were expecting they could sort out the problem with their spoilers and reverse thrust and stop it in the normal way, without giving the passengers a shock.

[0]https://www.ttsb.gov.tw/media/4912/ci-202-final-report_chine...

edit: that chart's x-axis is the aircraft's position on the 8500ft-runway, and most of the recording traces seem to begin at the point when it had touched down finally with all wheels

ysangkok• 5 years ago

hit the brakes very hard in the last few seconds

In direct law, is it possible to brake too hard and have the tires skid on the runway? Is it possible that the pilots were afraid of this?

I ask because people are characterizing direct law as "less smart". So how smart is it? Smart enough to include ABS?

FatalLogic2• 5 years ago

I don't know, but the computer had failed, the runway was wet, and they were confused, so, yes, it's not unlikely they were also afraid of skidding

oakmad4• 5 years ago

Oh 100%! Anti skid is only available in alternate and normal laws. Section 6.5 braking system of this document.

https://www.smartcockpit.com/docs/A330_Flight_Deck_and_Syste...

mertd• 5 years ago

How hard is it to make airliner lose grip? There is a lot of weight above the wheels and a lot of downforce from the wings.

noduerme• 5 years ago

I was a passenger on a JetBlue flight in the winter of 2000/1, where air traffic was being diverted from JFK due to a snowstorm, but for whatever reason (fuel?) we had to land there anyway. The runway was basically unplowed at that point. As soon as we touched down there was a sensation we were heading into a skid. I wouldn't really call it a braking skid... it the plane just started turning away from its angle of motion. The pilot somehow managed to slow down before we went off the side of the runway. Ended up stuck in deep snow, partially in a ditch. After what seemed to be some attempts at getting us out if the snow, we were evacuated off the slide. A couple people movers were brought out which we got into, amd which themselves became stuck in the snow on the runway for an hour ... fun times.

kayodelycaon• 5 years ago

Aircraft anti-skid is more complicated than a car. There are a lot of hydraulics and sensors working with extremely high loads.

To simplify how things work, there are two sets of systems in the plane.

There are the computers controls that move all of the surfaces. They have no connection to the various other sensors, because they only move things as they are ordered to. These form the base flight-by-wire system.

On top layer, you have the three flight computers handling all of the automation. A triply redundant system with all of the plane's sensors available to them, not just the sensors in the braking system.

So, the ABS is handled by the flight computers and the flight computers are their own backups. The automation will attempt to degrade gracefully into alternate law. If they all go, the plane reverts to direct law and the pilots interact with the base fly-by-wire system which has little to no automation.

Failure of the flight computers are rare. Every other part of the braking system is less reliable than the flight computers.

From another angle, if a failure caused the flight computers to crash, is there also a problem with the braking system? By having a clear, defined failure mode, a pilot only needs to be trained to land the plane with manual braking.

When the flight computers drop out, the fly-by-wire system becomes directly connected with the flight controls. This includes the anti-skid functionality.

With the above design, it doesn't make a lot of sense to add a layer of complexity between the flight computers and the fly-by-wire system. The redundant flight computers are the backup systems. They can run with partial functionality. If they all fail, the plane reverts to a known, extremely well tested, working systems.

There are multiple overlapping failure modes already. Adding another failure mode is a bad idea.

oakmad4• 5 years ago

I wonder how much was just being « used » to auto braking assistance and what felt right.

pseingatl• 5 years ago

Airbus: what is it doing now?

aomobile• 5 years ago

I wonder how the pilots would have reacted if the computers had crashed 10-20 seconds earlier. Would they have landed or would they go up again to wait for reboot?

bonzini• 5 years ago

Difficult to say, since the computer crash was linked directly to having just touched down. 10-20 seconds before there was no disagreement because neither computer has detected that the wheels were on the ground.

fnord77• 5 years ago

The root cause was determined to be an undue triggering of the rudder order COM/MON monitoring concomitantly in the 3 FCPC. At the time of the aircraft lateral control flight law switching to lateral ground law at touch down, the combination of a high COM/MON channels asynchronism and the pilot pedal inputs resulted in the rudder order difference between the two channels to exceed the monitoring threshold. The FCPC1 failed first.

In lay-programmers terms, this sounds like a race condition. Is that correct?

zaarn4• 5 years ago

Not quite. The computers disagreed, they didn't race. Likely cause might be that the sensors responsible for detecting touchdown might have been rusty or failed. The computers aren't racing towards ground law here, they switched to ground law at different times sufficiently apart that the monitoring watchdog turned them all off for commanding the aircraft to do three different things.

Imagine it more like website and it's hosted by three servers with a replicated database. A monitoring tool checks that the number of entries in each server's database is the same. If one server has a different number, the tool turns it off, it now requires a human to bootstrap the database again. If two servers disagree the website goes offline, because it's no longer possible to tell which server has correct data and not operating is cheaper than the man hours required to puzzle the data back together.

In this case, a likely cause might be that suddenly the network latency between the three servers got suddenly very large (cable damage maybe?) and now all three no longer agree on the dataset. The servers are shutdown.

5faulker• 5 years ago

Good thing that this was on a smaller airplane, otherwise it could have been a larger disaster.

danielschonfeld2• 5 years ago

Feels like there might be more to the story than is being let on.

Curious why the PF has to specifically ask before landing for the spoilers to be called, to tell if he's touched down. AFAIK it's actually common Airbus procedure to called Spoilers and Reversers and deceleration after landing. Also telling whether or not you touched down isn't really a problem... even for the smoothest/softest of landings. Then there's the PM calling out "center line" at 130 feet...

jimnotgym• 5 years ago

I note there was a tailwind serious enough to reduce breaking performance, and also that it is possible to land in the opposite direction on the runway in question. Is the practice of landing into the wind ignored within certain parameters?

gsnedders2• 5 years ago

In general, aircraft are certified to land/takeoff with tailwinds (and crosswinds, etc.) up to a certain speed. You don't want to be changing runway direction all the time, after all.

Ultimately, it's up to the crew on board to determine the landing distance required for the current conditions (including the wind—whatever direction that is!), and if they don't believe the conditions are safe they should not proceed with the landing. They can, of course, request the opposite runway, though obviously if there is frequent traffic ATC is likely to refuse unless they want to change the direction for all traffic.

ddalex2• 5 years ago

Commercial piloting is hours of boredom with few moments of raw sheer terror.

tim333• 5 years ago

Good thing they failed on touchdown and not up in the air.

Incident: Airbus A330 at Taipei, primary computers failed on touchdown (2020)

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