CAA bans Boeing 737 max 8

The key to the problem is MCAS system giving an un-commanded nose up or nose down during critical flight phases.

This could be due to:

a/ hardware fault - faulty AOA sensor
b/ software fault
c/ combination of both

Of the choices, I think that b is favourite as it's unlikely that the AOA sensors are going faulty at this rate.

Edited to add:
the AOA sensor is just a little vane connected to a potentiometer giving as current that tells the MCAS computer what the AOA is relative to the airflow. Works akin to a car throttle position sensor.

The FAA realise that if one of these goes down coming out of Heathrow or Gatwich then it's likely to make a large hole in West London with massive loss of life on the ground. The two planes that have crashed have been 6 and 13 miles after take-off respectively.

Westbound this would take out somewhere around the Windsor / Slough or maybe Legoland
Eastbound: Twickenham, Richmond, Kingston
Northbound, anywhere as far as Watford
Slough or Watford. Either is fine with me
 
As they say, and pardon my French, shit just got real for Boeing.
And the FAA. Has now become very clear that there is a link between the regulator and a supplier. Virtually all the main carriers (and countries) grounded them for safety pending investigation, yet the FAA carried on with their "nothing to see here, move along". Time is way overdue to drain the swamp.
 
And the FAA. Has now become very clear that there is a link between the regulator and a supplier. Virtually all the main carriers (and countries) grounded them for safety pending investigation, yet the FAA carried on with their "nothing to see here, move along". Time is way overdue to drain the swamp.
The US defence minister is a former long time Boeing vice president. Boeing are also one of the "national champions" who are being promoted by the White House. I don't know if there is any connection these two and the reluctance to ground one of Boeing's key products.
 
Interesting that the US grounding is being reported as initiated by Trump, rather than the FAA.
Well he's guaranteed to know more about aircraft than they do.
What with him being the bigliest cleverist person ever to have lived like.
 
Interesting that the US grounding is being reported as initiated by Trump, rather than the FAA.
It is possible he took exception to Boeing's line that they had a software fix, but the shutdown of Government departments meant approval for the fix from the relevant Federal agencies had been delayed, and they hope to be able to deliver it soon.
 
Software engineering isn't really engineering at all. It's more of an art than a science.

Civil engineers can chuck design data into a computer to prove mathematically that their bridge won't fall down. Electrical engineers can model circuits using matrices to prove mathematically that their circuit won't go up in smoke. Mechanical engineers can analyse the stress in every joint in a structure to prove mathematically that it wont break in a high wind.

Software "engineers" can't rely on any sort of mathematical tool to validate their designs. The job is more dependent on knowledge and experience than other types of engineering.

Of course, knowledge and experience comes at a price. If a software fault is to blame for this crash, it will be very interesting to see who wrote the code. Perish the thought that it might have been some damned jolly fine offshore enterprise that put in the lowest bid and employed programmers who have never flown on an aircraft, let alone programmed one.
There are methods of mathematically proving software correct. These are known as "formal methods".

There are standards for developing software for aircraft which claim to use formal methods, but they don't seem to be quite what most people in the software industry outside of that field understand the term to mean. They do however involve a systematic approach to design, review, and verification.

"Formal methods" as the term is understood to mean in most of the software industry, hasn't caught on much however because of several practical problems with it. The first is that it isn't possible to use proper formal methods for anything other than very simple applications because of the scale of complexity.

Another problem is that it even if you can apply automated formal methods, it just pushes the problem out from the target to the verifier. How do you know that the model you are using for verification is correct and free of bugs?

A third problem is that a lot of bugs, especially when hardware systems are included in the scope, are due to incorrect concepts or incorrect understandings about how the system will behave in the real world. There may be no solution to this sort of problem, even in theory.

In most of the modern software industry (I will leave aerospace and military out of the equation here) current best practice revolves around automated testing. You write a small bit of software which is supposed to do something you want, and you also write another small bit of software to test the first bit. In some systems you write the test first and the software that is actually intended to do something second. Automated testing can be integrated into the development process such that checking in some new code automatically kicks off the testing system.

This approach can work pretty well, but it does have some shortcomings. The obvious one is that it doesn't test for problems that you didn't think of testing. Another is that if your ideas about of how something ought to work have some holes in them, then you may test for the wrong results.

Another much bigger problem is that writing the tests doesn't tick many milestone boxes on the project manager's charts, so this part of the project gets put off until "later", and "later" never comes because of course once the project gets shipped there's no more manpower budget for testing until the big panic starts when customers start filing bug reports. Related to this are situations where the tests get written, but when they fail the software the tests get turned off because dealing with them interferes with progress. A further problem is where software gets changed but the accompanying tests don't, they just get turned off.

I expect that these types of problems are less prevalent in fields where safety is heavily regulated, as there are outside parties looking to see if anyone is bypassing or ignoring proper procedures. All of that regulatory oversight though takes time and costs money which is why it isn't used except where required by law.
 
Yes it is common practice (for some things) but - there is a very robust Paper trail - its not a case of simply pinching the lamp off your focus because the wife needs her Fiasco in the morning.
For example a CVR needs to be removed and serviced after X many hours - You cant fly without the CVR so when you send it off to Rockwell - you fit one from your stores - when Rockwell return your now serviced CVR you will fit it to the next aircraft that needs it - Ditto numerous other parts

As for bogus Parts - There have been issues -
But theres been issues of new parts that were substandard with falsified paper work.

Theres probably nothing you can do to stop unscrupulous people fitting dodgy parts / parts from dodgy source's.
But should** it be discovered heads will roll - people are looking at spending 10 years inside which is something of a deterrent

**In the event of an incident - it will be discovered in which case the relevant Authorities will spread the pain around rather liberally even if its not associated with the accident.
A company I worked with had an incident resulting in a helicopter making a somewhat heavy and unplanned landing. It was determined that a part was several hours out of life - this part had nothing to do with the problem - it was noted when they went through the aircraft records.
Subsequently because of this oversight (and it was an error) the Authority extended the investigation and audited the rest of the fleet and everyone and everything that had looked in its general direction
It's not for nothing that aircraft stores are kept locked and shop floor people kept out. And that was in aircraft seat manufacturers I've worked for.
Slough or Watford. Either is fine with me
And Legoland.
 
Interesting that the US grounding is being reported as initiated by Trump, rather than the FAA.
The news reports that I have read said that Trump announced it, but the decision was made by the US FAA.

For example, here's the BBC link which someone previously provided: Boeing grounds entire crash aircraft fleet
The sub-heading says that Trump announced it.
President Donald Trump has announced that the US will immediately ground all Boeing 737 Max aircraft following the crash of an Ethiopian Airlines jet.
But the actual story said that the US FAA made the decision to ground the planes.
The Federal Aviation Administration had previously held out while many countries banned the aircraft from flying over their airspace.
But it said on Wednesday it was suspending the aircraft after analysing new data gathered at the crash site.
Getting your name into the news in connection with a decision doesn't mean you were the one to make the decision.

Have you got a reference to something that said that the FAA were not the ones to make the decision?
 
It is possible he took exception to Boeing's line that they had a software fix, but the shutdown of Government departments meant approval for the fix from the relevant Federal agencies had been delayed, and they hope to be able to deliver it soon.
The optics of that are not going to look very good if Boeing uses that as a defence against being held responsible for the second crash.
 
The news reports that I have read said that Trump announced it, but the decision was made by the US FAA.

For example, here's the BBC link which someone previously provided: Boeing grounds entire crash aircraft fleet
The sub-heading says that Trump announced it.


But the actual story said that the US FAA made the decision to ground the planes.


Getting your name into the news in connection with a decision doesn't mean you were the one to make the decision.

Have you got a reference to something that said that the FAA were not the ones to make the decision?
Sky News on their app clearly stated that Trump made an emergency notice of prohibition, followed by Boeing grounding the fleet. No mention of FAA.
 

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