Gary - you are so WRONG - an op-amp is an AMPLIFIER, not a computer - just packaged in a handy little bit of plastic and silicon. I suppose in you dream world a 1.5MW RF amplifier is a computer, as is light switch.

---

Bob Smith
Member of Seti PIPPS (Pluto is a Planet Protest Society)
Somewhere in the (un)known Universe?

The aircraft trim should be maintained at all times. Not doing so reduces the safe control envelope for the pilot.
Deactivating the electrical controlled trim means the pilots must do more work to manually adjust the trim.
So yes, an aircraft can safely land with the pilots using manual trim.

I thought it might be. However, how many pilots are of the Jeff Capes or Arnold Schwarzenegger type?

The manual stabilizer trim on a Boeing 737 Max or NG require at least two person turning the trim wheels when the air speed is moderate. In the case of the crashes the airspeed was nothing but moderate. One of the planes got help from a pilot passenger so there was THREE people that was trying to use the trim wheels. Didn't work...
https://youtu.be/xixM_cwSLcQ?t=442

The aircraft trim should be maintained at all times. Not doing so reduces the safe control envelope for the pilot.
Deactivating the electrical controlled trim means the pilots must do more work to manually adjust the trim.
So yes, an aircraft can safely land with the pilots using manual trim.

I thought it might be. However, how many pilots are of the Jeff Capes or Arnold Schwarzenegger type?

The manual stabilizer trim on a Boeing 737 Max or NG require at least two person turning the trim wheels when the air speed is moderate. In the case of the crashes the airspeed was nothing but moderate. One of the planes got help from a pilot passenger so there was THREE people that was trying to use the trim wheels. Didn't work...
Runaway Stabilizer!! How to stop MCAS

Good link thanks. Indeed, to me that manual trim looks to be impractical and unworkable.

For the flight with three pilots in the cockpit when MCAS failed, I believe the third pilot helped due to having the third human brain to allow thought and diagnosis to then instruct the two pilots through the 'work around'. The two pilots flying were overly busy keeping the plane in the air and in being bombarded with a bewildering cacophony of multiple alarms...


Such a confusing situation should never have been encountered... And certainly never multiple times by multiple crews to their death and the death of all passengers and crew.


All in our only one world,
Martin

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Gary - you are so WRONG - an op-amp is an AMPLIFIER, not a computer - just packaged in a handy little bit of plastic and silicon. I suppose in you dream world a 1.5MW RF amplifier is a computer, as is light switch.

Rob, very very wrong. Set gain on OP amp to two. You now multiply by two. Set gain to 1/3, you now divide by three. Analog computer.

You do know that six discreet transistors builds a nice OP amp. Of course you can pack them into a chip. The entire field of digital computing depends on OP amp like circuits!

You build gates for your digital computer on the silicon die using OP amps. One bit into the gate is the signal, the other bit into the gate sets the gain. Now you have a functional AND gate. Pick the output at a different spot in the OP amp and you have a NOR gate. Now you build a digital computer stringing them together.

... Set gain on OP amp to two. You now multiply by two. Set gain to 1/3, you now divide by three. Analog computer...

Gary,

To follow you pedantry...

Nope.

The op-amp is the amplifier, a component. It is just an amplifier, just a clever collection of transistors configured as an amplifier. Usually designed to have 'in effect' what can be assumed to be infinite gain.

Add some surrounding circuitry and you can use that amplification for various functions.

The combination of circuitry plus an amplifying or comparator device can be designed to perform functions on signals.


As to who in this thread is somehow 'right' or 'wrong' for some pedantic description is irrelevant.

Unless you have some new circuitry to show us all?

Or please give a reference if my description is inaccurate?


And now... Enough of the word games and back to the thread please?

Regards,
Martin

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Six??? The very simplest op-amp only uses ONE, next up is a pair,and then three - all the way up to several dozen.

Gates - the simplest gate is a diode - a bit more complex and we go to diode arrays, then to combinations of diodes and resistors.... (edit - that should be transistors - finger and phone trouble)
Indeed some of the oldest gates (as used in the very first computers consisted of arrays of diodes, triodes and pentodes (with a good few resistors and bus-bars for good measure).
Yes you can make gates using transistor arrays, or combinations of transistors or diodes, or even magnetic reluctors (never could get my head around those...).

[edit]
Sorry Martin - I'd written my reply but got caught by a phone call to sort out a problem someone is having with a "small" power switching problem they are having with a 5MW inverter - the latest batch of IGBTs they've received are at one limit of their spec and let the smoke out too soon. Nothing too serious, just check the value of the capacitors in part of the firing circuit to calm that waveform down a bit and they'll be OK.

---

Bob Smith
Member of Seti PIPPS (Pluto is a Planet Protest Society)
Somewhere in the (un)known Universe?

[edit]
... a phone call to sort out a problem someone is having with a "small" power switching problem they are having with a 5MW inverter - the latest batch of IGBTs they've received are at one limit of their spec and let the smoke out too soon. Nothing too serious, just check the value of the capacitors in part of the firing circuit to calm that waveform down a bit and they'll be OK.

So...

You're the one that blacked out a good chunk of the UK last Friday?!...


;-)

Cheers,
Martin

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I'm still awaiting my session in the B737MAX simulator - I've seen my contact recently and he's hopeful that a slot will come up for a "demo-ride" near the end of October as they are still trying to bottom out the "new" fault while making sure the "fix" for the existing MCAS debacle is "safe and secure".
It does look as if Boeing are investigating adding a third AoA sensor (bringing them in line with what Airbus did a good few years ago...). He thinks that some authorities will be pressing (or are pressing?) for the B737max to be categorised as a "different type" to the earlier generations unless the B737MAX has "certain additional features" added (whatever they may be).
Personally I think this is going to be the end of the B737 family until such time as Boeing grasps the nettle and move the entire avionics package onto a more modern more redundant platform. While the '286 was a good platform at the time of the last major cross-family update of avionics it is certainly starting to show its age now. And that is far from a cheap path to tread :-(

---

Bob Smith
Member of Seti PIPPS (Pluto is a Planet Protest Society)
Somewhere in the (un)known Universe?

This thread is veering off into discussion of individual components, which IMHO is not necessary.
Whatever way one can slice it, a system failed, not once but twice with the result 346 dead.
Unlike other forms of transport, a passenger aircraft HAS NO lifeboats or parachutes to escape from, therefore its safety & control systems need to be standard, tested & proven.
Nice to see Rob confirm an earlier post of mine.
From design year to date, the 737 is 55 years old. Well past its sell by date.

After quite a thread distraction and after more fruitless web searching...

So... What is/was this mystery flaps/flight-stabilization fault?...

Here's a worrying Boeing 737 MAX mystery that I've not been able to find anything further about on various web searches:


Additional Software Problem Found In Boeing 737 Max Control System

Boeing confirmed to The Washington Post that it had found a second software problem that the Federal Aviation Administration has ordered fixed - separate from the anti-stall system under investigation in the two crashes...

That additional problem pertains to software affecting flaps and other flight stabilization hardware and is therefore classified as critical to flight safety, said two officials who spoke on condition of anonymity to discuss the ongoing probe.

The realization of a second software problem explains why the timeline that Boeing projected publicly last week for getting hundreds of the aircraft airborne again has slipped...




So... What is that second flight software fault that was found? And in what way critical to flight? And how many passenger flights has that software been flying with what real risk??

Anyone able to sleuth further details?


All in our only one world,
Martin

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Not so far, but it will be interesting to know.
One update that is surely required, yet see no mention anywhere.
If MCAS is deactivated, shouldn't there be a backup system in place to provide electrical power to the trim motors?
Had that been an option at the time, the possibility could have been 2 normal flights.

Martin and Rob, I suggest you both learn what an OP AMP is first. Just any amplifier is not an OP AMP, something you both seem to be missing. Try ISBN 07-064917-0 Operational Amplifiers Design and Applications, Jerald G. Graeme, Gene E. Tobey, Lawrence P. Huelsman, Ph.D. prepared by Burr-Brown Research Corp., Mc Graw Hill, 1971. Has a nice space on my bookshelf.



Now all of that is a irrelevant to the question of hacking an Airbus. Martin has said there are three identical computers that do the control function, or translate the pilot input into actuator output. All the level checking and voting actually doesn't matter to hacking the plane*. Since all three computers are identical if you can hack one, you can hack all of them as they are identical. So you load your hack on all three, ignore the pilot input and produce valid signal levels on the output that do what you want, not what the pilot wants. As you are doing it on all three computers at once, they vote valid and pass the output on, and as you want control, not destroying an actuator, the output level passes level comparison. All the one way signal stuff is fine, but those are the operational signals, not the programming signals. If the computer can be flashed, that is a two way digital bus. Get control and you have the airplane. (If it can't be flashed then a software update would require a ROM chip swap. Somehow I doubt that is the design.) But in any case a nation state that wants to hack can either bribe a maintenance person or place a sleeper agent as a maintenance person to gain access to the avionics bay and hence the two way digital bus. That "update" might not replace the flight control software, but only make it so that it can be replaced from say the entertainment system on the aircraft in flight, e.g. a smart device with a USB cable to get to the plane systems and also connected to the outside via the onboard wi-fi.

It may not be easy and joe blow hacker may not be able to get access, but a Nation State can buy an airbus and put it on a test stand in a wind tunnel to not only hack in but to perfect the process to take the airplane to where they want if it has enough fuel onboard. It is not hack proof.



*the voting and level comparison only matters to a failed component and that is what is was designed to isolate.

It would be perfectly possible to have an MCAS-like system that could be deactivated and not affect the pilots's trim toggles - in my mind (no decent schematics available to me) it should be possible to put the "MCAS control input" as a separate input to a voting system of some sort and thence to the horizontal trim stabiliser motor(s), or to only turn the control signal from MCAS off without affecting the pilots's ability to use their trim toggles.
Doing what Boeing apparently did is nothing short of stupid - turning off what at the time was classified as a "non-safety system" isolated one of the pilots's flight controls (the trim toggles).

As to the flap control - that could well explain why my contact refused to be drawn on what the "second problem" is/was - not enough is/was known to him so whatever he said would be speculation.

---

Bob Smith
Member of Seti PIPPS (Pluto is a Planet Protest Society)
Somewhere in the (un)known Universe?

... Just any amplifier is not an OP AMP, ... Try ISBN 07-064917-0 Operational Amplifiers Design and Applications, ..., 1971. Has a nice space on my bookshelf.

Far easier is:

Wikipedia: Operational amplifier

Note the additional circuitry needed to usefully use/configure an op-amp.

Now all of that is a irrelevant to the question of hacking an Airbus. Martin has said there are three identical computers that do the control function, or translate the pilot input into actuator output. All the level checking and voting actually doesn't matter to hacking the plane*. ... gain access to the avionics bay and hence the two way digital bus. That "update" might not replace the flight control software, but only make it so that it can be replaced from say the entertainment system on the aircraft in flight, e.g. a smart device with a USB cable to get to the plane systems and also connected to the outside via the onboard wi-fi. ...

*the voting and level comparison only matters to a failed component and that is what is was designed to isolate.

We have the very worrying comments for my (personal opinion) gobsmacked disbelief at what appears to be Boeing's reliance upon a mere firewall to keep their digital avionics systems (supposedly) isolated from the big bad outside cybersphere.

I have never looked to see what Airbus do to keep their avionics protected from external interference/hacking. Anyone know for sure? Any readable descriptions?


Gary,

Your religious defense of Boeing appears to be a labor of love and passion! Do you have all your shares or pension tied up with them? Or are you otherwise sponsored by Muilenburg?


Aside regarding Boeing: Dennis Muilenburg: 5 Fast Facts


All in our only one world,
Martin

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What is that missive got to do with the Boeing 737 Max incidents?

What is that missive got to do with the Boeing 737 Max incidents?

Gary appears to be trying to suggest that somehow other aircraft manufacturers are just as bad as Boeing....

Myself, I'm not sure about the op-amp dialogue other than somehow he's trying to suggest that analog signal voting as used for fail-over redundant systems can somehow be hacked?

(Yet also note that for the Boeing 737 MAX, there is no fail-over redundant system for MCAS yet...)


Don't know... Gary, what are you suggesting please?

That somehow Boeing didn't kill the most passengers and crew in the last 12 months, TWICE over?



All in our only one world,
Martin

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I look at things from ground level.
I can't forget a documentary on flight 1549.
2 passengers being interviewed at a family gathering.
They had a white board.
Just 2 passengers - Father & son.
Every one at that gathering had drew their link to the 2. It totalled 56. So lets' pro-rata that.
346/2x56=9,688 people distressed.
Ain't statistics a bitch.

Drilling down to an individual component is pointless.

... Every one at that gathering had drew their link to the 2. It totalled 56. So lets' pro-rata that.
346/2x56=9,688 people distressed.
Ain't statistics a bitch.

Drilling down to an individual component is pointless.

There is more than just a single component at play in the Boeing 737 MAX tragedy...

And there are more than just those 10,000 people distressed.

As an engineer, I'm distressed that such a crass disaster could happen. TWICE over!!

As a certain multi-million dollar person has tried to excuse: Indeed there is a chain of events in such disasters... A chain that hopefully will be followed up right up to the very top including right up to the effects of Trump's cost-cutting policies neutering the FAA...

No excuses.


But then again, there are politics and the expensive games that lawyers play...

All in our only one world,
Martin

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... Airbus. Martin has said there are three identical computers that do the control function, or translate the pilot input into actuator output. ...

Yikes! Where have I said that?

Note that using identical hardware and software can lead to what are called common mode faults. For anything safety critical, that is still a big no no!

Hopefully, all aircraft manufacturers are better than to do such dangerous silliness as to risk single source or common mode faults for anything critical...?


All in our only one world,
Martin

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Here's an interesting question and associated snippet for the Boeing 737 MAX:


Why can't Boeing simply remove the suspected software in the Boeing 737 Max?

"... Thus the problem was not in the Angle of Attack sensor, but rather in corrupted data itself. This data came from the Digital Flight Data Acquisition Unit (DFDAU).

My suspicion is that voltage surges, voltage irregularity or an out of phase generator caused errors in encoding data with the ARINC 717 databus..."


That is a rather good question but also that comment leads to an intriguing and worrying idea...

Anyone have any details on whether there might be data signal errors and if such errors are checked for?


All in our only one world,
Martin

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See new freedom: Mageia Linux
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