Lionair 610 crash

[fairbasa]

I found this video pretty useful in helping to understand trimming in the 737 and what JB is describing above:

 

[Deleted member 29185]

I thought you wanted terrain avoidance a few paragraphs ago.

It's not what I want, nor what I don't want, I simply asked a question as to whether commercial aircraft had it as I have no idea. What I do wonder about, is that your informed and appreciated responses come from an experienced pilot with the benefit of time and hindsight in addressing each issue (given we still don't know just what the original issue was) but not every pilot and/or first officer will have as much experience and I confess, as a regular commercial pax, I find it somewhat alarming that Boeing know of a problem that can happen with an A/P going off line (and you yourself confirm this happens due to any number of issues), yet Boeing's response is that the pilot(s) can fix it. If it turns out after the fullness of the investigation that it was indeed a contributing factor in this incident, then their "pilot can fix" solution is clearly flawed and may have cost 180+ people their lives.

 

[Berlin]

Haha, German news-site “Spiegel” was leading with the headline earlier today that basically read “Did the Computer cause the Lion-Air jet crash?” and I couldn’t help imagining an evil comic-like robot with a big monochrome screen head knock out the two pilots in the coughpit and frantically push some buttons to make the plane dive into the ocean .

They’ve since changed the title to something more along the lines of “Technical issues look more and more likely as a cause”.

 

[fairbasa]

The nose down trimming appears to have been caused by erroneous AoA inputs. This is resolvable using existing checklists which say to use the cut-out switches to stop the electronic trimming in manual flight. With that said, if my understanding is of the above is correct, it seems like it's not the best systems engineering.

Systems with a potentially high criticality of failure like this should be designed with multiple redundancies in mind, such as with UAS, if an erroneous pitot static reading occurs, it will use the two closest readings out of the 3. It's sub-optimal design for a single AoA sensor failure, even if recoverable using manual trimming, to cause such a confusing and high workload environment for the flight crew (stick-shaker, minimum speed bar, automatic nose down trimming and 4x different alerts). It's foreseeable that in such a scenario a crash would eventuate every xth AoA failure.

Back to the root cause of the erroneous AoA sensor data, if it was identified previously as the issue and recently swapped out (assuming the replacement was serviceable and installed properly), I wonder what caused it to continue to give bad readings?

Bad wiring?
Not actually a sensor issue but a computer issue similar to the QF A330 ADIRU failure?

 

[jb747]

It's not what I want, nor what I don't want, I simply asked a question as to whether commercial aircraft had it as I have no idea.

No, they don't. They do have terrain warning systems, but will take no action by themselves.

What I do wonder about, is that your informed and appreciated responses come from an experienced pilot with the benefit of time and hindsight in addressing each issue (given we still don't know just what the original issue was) but not every pilot and/or first officer will have as much experience.

I am very strongly anti the dumbing down of the job that is going on. Minimum hour cadets, in the right hand seat of a high performance airliner, is something that accountants love. It does not necessarily make for a good coughpit operation though. Now most of these cadets turn into good pilots, but an airliner coughpit is not the place to be getting your initial experience. Sadly, in these days of limited GA, and recruiters who don't like the military, this is the way it is.

Operating an airliner as a video game, using the autopilot for every approach, and engaging it immediately after take off is the mandated operating mode of many airlines. But this takes the day to day practice away from the pilots, giving it to an autopilot, which doesn't really need it. There are many failures which remove the autopilot from the mix. In an Airbus, such a loss with often be associated with simultaneous law reversions, so not only will the a/p not work, but we'll hand you an aircraft that isn't flying the way it was on every other occasion you've happened to hand fly it. On the other hand though, the loss of the a/p happens because keeping it in, with degraded function, is considered a worse option.

....and I confess, as a regular commercial pax, I find it somewhat alarming that Boeing know of a problem that can happen with an A/P going off line (and you yourself confirm this happens due to any number of issues), yet Boeing's response is that the pilot(s) can fix it. If it turns out after the fullness of the investigation that it was indeed a contributing factor in this incident, then their "pilot can fix" solution is clearly flawed and may have cost 180+ people their lives.

The a/p drops out because it is literally unable to remain engaged. It has lost data that it needs, or access to controls that it needs. If it could remain safely engaged, then I'm sure it would.

 

[Berlin]

I am very strongly anti the dumbing down of the job that is going on. Minimum hour cadets, in the right hand seat of a high performance airliner, is something that accountants love. It does not necessarily make for a good coughpit operation though. Now most of these cadets turn into good pilots, but an airliner coughpit is not the place to be getting your initial experience.

I dunno, but this gives me the creeps: It actually makes me surprised that there are so little accidents and, as an overall trend (I know, this year is turning out to be a rather sad outlier...), air traffic gets safer and safer. And surely, JB doesn't strike me as someone who'd be prone to sensationalise the issue.

 

[jb747]

Systems with a potentially high criticality of failure like this should be designed with multiple redundancies in mind, such as with UAS, if an erroneous pitot static reading occurs, it will use the two closest readings out of the 3. It's sub-optimal design for a single AoA sensor failure, even if recoverable using manual trimming, to cause such a confusing and high workload environment for the flight crew (stick-shaker, minimum speed bar, automatic nose down trimming and 4x different alerts). It's foreseeable that in such a scenario a crash would eventuate every xth AoA failure.

The 737 is a very old design, incorporating grandfathered ideas from the early 60s. I was surprised to find that it only has two ADRs...everything I've flown has three, and then a dumb backup beyond that. When you only have two readings to play with, which do you choose?

Back to the root cause of the erroneous AoA sensor data, if it was identified previously as the issue and recently swapped out (assuming the replacement was serviceable and installed properly), I wonder what caused it to continue to give bad readings?

Not actually a sensor issue but a computer issue similar to the QF A330 ADIRU failure?

Whilst the ADR of QF72 gave dud data, it was the flight control (FBW) response that was silly. The computers weren't voting on inputs. One is in charge, and the others are simply backups. I don't know how AoA data is processed in the 737, but it's an input to the ADRs in the Airbus (as are probes for sideslip, plus the normal air sensors).

 

[tgh]

I am very strongly anti the dumbing down of the job that is going on. Minimum hour cadets, in the right hand seat of a high performance airliner, is something that accountants love. It does not necessarily make for a good coughpit operation though. Now most of these cadets turn into good pilots, but an airliner coughpit is not the place to be getting your initial experience. Sadly, in these days of limited GA, and recruiters who don't like the military, this is the way it is.

Succinct summation , but I opine that it may take quite a lot more losses before the bottom line ceases to be trumps.
Perhaps a likely outcome to this latest accident is that the workload overcame them ; ie the capacity to simply aviate was usurped by the demands of the out of control automation.

 

[fairbasa]

The 737 is a very old design, incorporating grandfathered ideas from the early 60s. I was surprised to find that it only has two ADRs...everything I've flown has three, and then a dumb backup beyond that. When you only have two readings to play with, which do you choose?

Yes, that is a question with no good answer. But as you imply, whilst the 737 does have ancestry back to the 1960s, this was a new model, it should have modern systems and engineering controls. If this ends up being a single faulty AoA reading leading to this crash, Boeing shouldn't get out of it lightly.

 

[juddles]

I must say, I know so much more about "trim' than I did a couple of weeks ago....

 

[ermen]

how bad / complicated would an AOA failure be when coupled with the climb phase of flight?

i thought at say 30,000 feet an AOA failure / mis-reading is easily solvable.. but at 8,000 feet and climbing, thing could spiral out of control fast - perhaps not even time to consult the checklist / manual!

 

[juddles]

As we all should know, it is way too early to come to a verdict. But it scares me that there are automated systems in modern day aircraft that can make a perfectly sound aircraft be unflyable, even in perfect conditions, if the crew are not perfect in countermeasures to those software "glitches".

 

[Quickstatus]

Which countries have a culture of general aviation?

 

[juddles]

Which countries have a culture of general aviation?

All do. But cultural issues that are negative to best practise are very common.

 

[Quickstatus]

All do. But cultural issues that are negative to best practise are very common.

Agree but no not cultural issues.
I should have not use that word. Lets reword it to
Which countries have a significant general aviation industry

 

[OATEK]

Yes, that is a question with no good answer. But as you imply, whilst the 737 does have ancestry back to the 1960s, this was a new model, it should have modern systems and engineering controls. If this ends up being a single faulty AoA reading leading to this crash, Boeing shouldn't get out of it lightly.

As a layman, I can't help wonder if the 1960s design has been pushed beyond its limit. The points from jb747 about limited ADRs compared to other "current" models, the potential for a single sensor to start a series of events that can become uncontrolled. Has an old design beemn stretched too far, needing more computer-based protections, and as Fairbasa states leave Boeing in an unenviable position?

 

[flyer89]

I should have not use that word. Lets reword it to
Which countries have a significant general aviation industry

Depends on how you define GA. Australia, Canada, USA and swathes of Africa have a necessity for it. Large and remote areas of land require a general aviation industry. If you look at Asia and Europe though, nowadays the vast majority of pilots into airlines in those parts of the world are from a cadet program of some sort.

A friend of mine worked as an instructor at one of the flying schools of a major airline in this region. I need not repeat his view of the quality and aptitude of many of the students. Immediately after graduation they would be placed into the RHS of a narrobody jet.

 

[Quickstatus]

I believe it was airlines with a predominant 737 fleet which wanted Boeing to grandfather the technology to maintain pilot "type" certification. As soon as you substantially change the design, pilots need to be certified on the new airplane - which costs money which means they would have wanted Boeing to keep the design the same so that all their pilots can fly all the 737 whether new or old without recertification

I define GA as "flying for fun"

 

[OATEK]

I define GA as "flying for fun"

Perhaps there is a difference between General Aviation (GA) and general aviation (ga)?

 

[AviatorInsight]

@AviatorInsight
We now can see how the stabiliser is trimmed but how are yaw and roll trimmed?

Also what actually happens when trimming?. Does it alter the hydraulic pressures to achieve a “zero” stick position?. Say on the 737

I've included photos that I took today of the trim switches. It might make more sense. When the autopilot is engaged only the rudder and elevator trim are used. Aileron trim is almost never used and is prohibited with the A/P engaged. The aileron and elevator have a split switch and both must be used together to activate the system.

So when trimming on the elevators, the big trim wheels you can see will start moving, very during a trim runaway. The 737 doesn't use hydraulic pressure, rather, electric to activate the trim. The 'zero' position I believe you're referring to is no back pressure being held by the pilot. Unless it's you're talking about the control wheel being neutral with say an engine out, which will cause the aircraft to fly in a slight side slip.