Ethiopian plane crash

[TeamD]

kev1974 said:

TeamD said:

Munter said:

Starfighter said:

.

The first broken link in the chain is a crappy AOA sensor. That is hardware fault and needs a hardware fix.

Why not just have the software use both AOA sensors to tell if one has failed. The hardware backup is already there, and working. Just being ignored. Why not solve that problem?

Normally 3(minimum) sensors would be the best option for a software based fix. Let's face it, even if you have two sensors, which one is wrong? You, I, the computer, cannot make this determination, it's a coin toss.

You could make a very educated guess by looking at historic data for the two sensors and seeing if one had suddenly changed or gone unstable?

If you had three you'd want them to be in physically distinct locations as much as possible to avoid the possibility of a truck on the ground bashing or stoving two of them in unnoticed, and causing them to give similar but incorrect readings.

Educated guess could be an "outside limits" sort of thing, but would you really want stuff to be done on guesswork?

[George Smiley]

kev1974 said:

You could make a very educated guess by looking at historic data for the two sensors and seeing if one had suddenly changed or gone unstable?

If you had three you'd want them to be in physically distinct locations as much as possible to avoid the possibility of a truck on the ground bashing or stoving two of them in unnoticed, and causing them to give similar but incorrect readings.

That would make the programming very complex. Wait.... ai to the rescue

[TeamD]

George Smiley said:

kev1974 said:

You could make a very educated guess by looking at historic data for the two sensors and seeing if one had suddenly changed or gone unstable?

If you had three you'd want them to be in physically distinct locations as much as possible to avoid the possibility of a truck on the ground bashing or stoving two of them in unnoticed, and causing them to give similar but incorrect readings.

That would make the programming very complex. Wait.... ai to the rescue

No effing way.

Aka, artificial stupidity.

[kev1974]

TeamD said:

kev1974 said:

TeamD said:

Munter said:

Starfighter said:

.

The first broken link in the chain is a crappy AOA sensor. That is hardware fault and needs a hardware fix.

Why not just have the software use both AOA sensors to tell if one has failed. The hardware backup is already there, and working. Just being ignored. Why not solve that problem?

Normally 3(minimum) sensors would be the best option for a software based fix. Let's face it, even if you have two sensors, which one is wrong? You, I, the computer, cannot make this determination, it's a coin toss.

You could make a very educated guess by looking at historic data for the two sensors and seeing if one had suddenly changed or gone unstable?

If you had three you'd want them to be in physically distinct locations as much as possible to avoid the possibility of a truck on the ground bashing or stoving two of them in unnoticed, and causing them to give similar but incorrect readings.

Educated guess could be an "outside limits" sort of thing, but would you really want stuff to be done on guesswork?

Well not guesswork per se, but if you saw that one sensor followed the expected or predicted results over the last whatever minutes, or changed gradually, whereas the other one was either not changing or was reading wildly all over the place, it would give a good idea of which one of the two to place more faith in?

[George Smiley]

TeamD said:

No effing way.

Aka, artificial stupidity.

Don’t let LinkedIn hear you say that!

Whatever happened to fuzzy logic?

[George Smiley]

kev1974 said:

Well not guesswork per se, but if you saw that one sensor followed the expected or predicted results over the last whatever minutes, or changed gradually, whereas the other one was either not changing or was reading wildly all over the place, it would give a good idea of which one of the two to place more faith in?

Except critical redundant systems rely on at least 3 systems, call it crc if you will.

You can’t validate a working sensor based on just comparing two readings, you need a minimum of 3 data sources. Here preferably 4 but the 4th could be comparing to pitch/speed/altitude for a calculated sanity check

[TeamD]

George Smiley said:

TeamD said:

No effing way.

Aka, artificial stupidity.

Don’t let LinkedIn hear you say that!

Whatever happened to fuzzy logic?

Same old, same old mate

[TeamD]

George Smiley said:

Except critical redundant systems rely on at least 3 systems, call it crc if you will.

You can’t validate a working sensor based on just comparing two readings, you need a minimum of 3 data sources. Here preferably 4 but the 4th could be comparing to pitch/speed/altitude for a calculated sanity check

Not even, must be odd to achieve quorum.

[PRTVR]

kev1974 said:

Well not guesswork per se, but if you saw that one sensor followed the expected or predicted results over the last whatever minutes, or changed gradually, whereas the other one was either not changing or was reading wildly all over the place, it would give a good idea of which one of the two to place more faith in?

But what is predictable ? remember people's lives depend on the result, if you hit turbulence what then, what if one starts to drift slowly out of calibration, it sounds easy but I think it's harder than people think.

[TeamD]

PRTVR said:

kev1974 said:

Well not guesswork per se, but if you saw that one sensor followed the expected or predicted results over the last whatever minutes, or changed gradually, whereas the other one was either not changing or was reading wildly all over the place, it would give a good idea of which one of the two to place more faith in?

But what is predictable ? remember people's lives depend on the result, if you hit turbulence what then, what if one starts to drift slowly out of calibration, it sounds easy but I think it's harder than people think.

Eh?

There will be margins.

[B'stard Child]

TeamD said:

George Smiley said:

TeamD said:

George Smiley said:

mcdjl said:

Does your car have traction control/stability control? Does the fact that it has it mean that the hardware is rubbish?

In most cases no but in a 600 bhp car it is there to overcome a hardware issue

But do you only have one wheel sensor?

Just reminded me of a time I was reported for dangerous driving after doing a 360 after exiting a side road

500bhp and tc was on

Turned out a abs sensor had a pinched wire (new car) and this triggered some active yaw bks or something by applying the individual wheel brake and diverting power to outside wheel

Fortunately no one hurt and charges dropped but software caused that failure based on hardware

With so much power and torque you need these aids on road cars but when they go wrong you end up with YouTube videos of fun

So a limited slip diff is a hardware solution vs traction control based upon the abs sensors being a software solution in the ecu. Which one bit you in that ass?

I had to take my newest car off the road this year because somewhere in the sensor system it is getting a screwy message that the car is skidding or spinning a wheel - the TCM is correcting this by applying the brakes - it drives perfectly and there is no skid or spin of any wheels but randomly applies the brakes and then brings on the TCL.........

Technology is very clever till it goes wrong

I much prefer the control to be in the "operator" rather than the "overwatch controller"

[Starfighter]

Munter said:

Starfighter said:

.

The first broken link in the chain is a crappy AOA sensor. That is hardware fault and needs a hardware fix.

Why not just have the software use both AOA sensors to tell if one has failed. The hardware backup is already there, and working. Just being ignored. Why not solve that problem?

If the sensor had not failed them the aircraft would not have crashed. It was the primary cause of failure and the software issue came about because of this.

The initial Boeing system design was based on a 2 sensor input system and was not implemented. I would assume ( but do not know for certain) that a 2 sensor system would have some level of signal comparison and error reporting.

[TeamD]

Starfighter said:

Munter said:

Starfighter said:

.

The first broken link in the chain is a crappy AOA sensor. That is hardware fault and needs a hardware fix.

Why not just have the software use both AOA sensors to tell if one has failed. The hardware backup is already there, and working. Just being ignored. Why not solve that problem?

If the sensor had not failed them the aircraft would not have crashed. It was the primary cause of failure and the software issue came about because of this.

The initial Boeing system design was based on a 2 sensor input system and was not implemented. I would assume ( but do not know for certain) that a 2 sensor system would have some level of signal comparison and error reporting.

One or two is not acceptable for mission critical systems.

[Starfighter]

Boeing’s risk assessment placed MCAS in the second highest risk category and that requires 2 inputs.

[dvs_dave]

George Smiley said:

Dvs_dave did you give your kids beef burgers during the bse crisis? Are you sponsored by Boeing?

It is a hardware fault
It is. A result of using an airframe years beyond the best before date
It is a result of using software to overcome hardware and that always results in failure
Will you take your family on the first max flight?

You’re being dramatic and silly. It is not a “hardware fault”. It’s a case of attempting to make something appear to perform a certain way when in reality it doesn’t.

Boeing attempted to make the MAX feel and behave the same as the NG to existing pilots. To make that possible, the MCAS was installed, in essence to mask the altered flight envelope characteristics the MAX actually has over the NG.

Taken in isolation there is nothing particularly wrong or dangerous with the MAX’s flight envelope. i.e. no “hardware fault”. It’s just different (and specifically at high AoA) to that of the NG. However, Boeing in their efforts to mask it’s true flight envelope has resulted in this debacle.

Put it this way, if the MAX had been released without the MCAS, and the pilots consequently had instead been properly trained to fly it, these two accidents simply wouldn’t have happened.

But go ahead, keep on not really getting it and shouting at everyone about how you’re right and everyone else is wrong.

Edited by dvs_dave on Thursday 25th April 06:19

[Lemming Train]

You're wasting your breath Dave. Half of this thread is made up of armchair experts banging on about this alleged hardware nonsense and it's become rather tiresome.

A few software changes, wire up the 'other' AoA sensor full-time, flight test the changes, write some extra blurb in FCOM. FAA will be happy with that and rubber stamp it; the rest of the authorities will follow suit shortly after. Max will be back in the air and all the drama forgotten about within a couple of years.

[Starfighter]

Agreed,however, that still leaves the hardware fault.

It appears that the AOA sensor failure rates are beyond what I would expect. What is the cause of the hardware failure. What is being done to correct this and what is the plan to swap out or repair the sensors at risk?

[Speed 3]

Starfighter said:

Agreed,however, that still leaves the hardware fault.

It appears that the AOA sensor failure rates are beyond what I would expect. What is the cause of the hardware failure. What is being done to correct this and what is the plan to swap out or repair the sensors at risk?

"appears" without an evidence base. Do you know what the MTBF is on this unit for the global fleet ?

We don't yet know whether the AOA sensor failure was for internal or external reasons e.g. impact damage. There was was speculation in this crash from an "insider" that it was the latter i.e. suspected birdstrike.

[768]

dvs_dave said:

Taken in isolation there is nothing particularly wrong or dangerous with the MAX’s flight envelope. i.e. no “hardware fault”.

There's no hardware fault when a battery overheats and a fire starts then? The software works fine when the hardware sensor isn't broken.

[anonymous-user]

Lemming Train said:

You're wasting your breath Dave. Half of this thread is made up of armchair experts banging on about this alleged hardware nonsense and it's become rather tiresome.

A few software changes, wire up the 'other' AoA sensor full-time, flight test the changes, write some extra blurb in FCOM. FAA will be happy with that and rubber stamp it; the rest of the authorities will follow suit shortly after. Max will be back in the air and all the drama forgotten about within a couple of years.

Completely right.

WTF are some of these people banging on about. They clearly don’t know what they’re talking about and actually making the thread rubbish.