8 years ago, An Airbus crashed due to a blocked' AOA sensor- which fooled both the pilots AND HALBUS .
So a few years later during gestation-certification of MAX, Boeing played word games re critical definitions in how failures affect safety of flight- which allowed a single point ' failure' to take control from pilot ( for the first time ever ? ) and then decdided to not notify anyone via some oversight or creative pencil whipping

https://news.aviation-safety.net/201...-check-flight/


Report: blocked AOA sensors caused loss of control during A320 check flight

note this was with experienced pilots !!

Wonder if stick shaker noise will mask trim wheel clicking

Isn't this rather similar to a Lufthansa A321 incident that occurred Nov 5th 2014, near Bilbao, (Spain), where the aircraft experienced a rate of descent of 4,000 FPM before the pilots got the aircraft back under control?

Incident recorded here: https://avherald.com/h?article=47d74074

And here: https://aviation-safety.net/wikibase/wiki.php?id=171411

Possible, especially if you get some EGPWS warnings.

That very same allegation was also made 45 years ago after the Turkish DC10 went down out in the forest of Ermenonville outside Paris, France. Could the Turks be trusted with such a technological marvel. Were they not out of their depths. That as we all now know was far from the truth, the real cause was a web of corruption, lies and deceit that shook the aviation industry to its core. Have a look how the Turks have fared since then. How about THY now could anyone say they are out of their depths.

First time poster here... I've read the first 20ish pages and last 5.. and I haven't seen it mentioned... I'm just an armchair observer, so I'd welcome some clarification on this

AoA vs pitch hasn't been mentioned, and while they're related, I'm quite certain they're not the same thing, and from reading the posts it sounds like the two terms are kinda used interchangeably..
AoA is the angle at which the air meets the wing, pitch is the angle at which the plane is flying relative to level.
boeing.com/commercial/aeromagazine/aero_12/whatisaoa.pdf

Depending on inputs, load, CoG,thrust, and configuration (Slats, flaps) you can keep the plane flying level but have various AoA's?

From this, it would seem that pulling back and nosing up (in and of itself) does little to change the AoA unless you're increasing the lift from the wings.


silverstrata I've really enjoyed your posts throughout this thread :)

MCAS.. to me, it sounds like it has far too much authority to do what it wants.. perhaps if it was limited to half (or quarter, or whatever) the authority it has currently it would still be functional but not provide so much input that the pilots have to be superman pulling on the stick to negate what it's doing... Now at the risk of assuming, does it have an indicator that shows when it's active and how much it's compensating? An intermittent input from MCAS is also bound to be confusing, but that's been said a few times.

What I know is at 1000ft AGL I wouldn't want any automation nosing me down unexpectedly. First, realize something is wrong, Pick up the book, find the page, read the troubleshooting procedure and then start doing something about it, no matter how much training I have.

All this is moot if the MCAS wasn't at fault here of course.

basic lever - the shorter the body length and the shorter the length from CG, the more ' force' is needed to tilt ( aoa ) or stop yaw ( if one engine out ). The longer the body- distance from CG, the less the force needed for normal AOA correction or yaw correction. Since the force needed is generally a function of size or AREA acted on by air pressure/lift - a longder body can allow a smaller area for control surfaces ( overly simplified ) then come the cost of designing a new smaller area or simply staying the same as current production, etc

And I think you ment the horizontal stabilizer- not the elevator ??

And if yoiu not the hight of the smallet airbus VERTical stabilizer it is longer than the longer airbus - for generally the same reasons

I saw the video. I stopped counting the passes after a couple seconds as it was way to difficult. So I looked at the other things going on, saw the gorilla immediately. But then I knew it was a trick video.

But, I must say, if anyone trying his best to count the passes couldnt see the gorilla, then I think the expectatations on what a cockpit crew are able to do in a high stress situation with a lot of stuff going on in the cockpit has to be signifcantly decreased.
Scary indeed.

maybe
For example

https://news.aviation-safety.net/201...-check-flight/

Hi, another question from SLF and PPL, hope you dont mind.
I have followed this thread from the beginning and only seen this question asked once with no definitive replies.
How many other 'patches' are there on aircraft such as the MAX or that matter any aircraft from any manufacturer (particularly old designs dragged into the modern age to avoid complex certification) waiting in the background to cause future problems?
Does the situation with Boeing and the MAX possibly require a detailed review of all other aircraft system updates and work arounds to see if another similar issue is waiting in the background for exceptional circumstances?
One would like to think not but this thread indicates this is possible.
I propose this scenario (from insufficient technical knowledge to know the answer - but just as an example so please don't jump on me too hard). The Weight on Wheels sensor. Does it have multiple redundancy? Does it have one sensor each UC feeding one pilots computer and if so does it have a cross check system? What happens in the event of a sensor failure? I am only using this as an example as it springs to mind. No doubt hundreds of other possibilities exist.
If you lock all the toilet doors simultaneously, does the pilots coffee machine stop working?

Finally another small question, how strong is the drive motor on the auto trim on the MAX or similar? Could you stall it out by grabbing the spinning trim wheel or will it try and take your fingers off?

Yes, I am aware of the moment arm and how that affects the size requirement, especially for the rudder.

I had in mind the size of the elevator compared with the full horizontal stabilizer.

I tried to measure the relative size on the drawings, as far as they are accurate, which I ofc dont know for sure.
I get the A320 elevator is marginally larger than 1/3 of the full horizontal stabilizer including the elevator.
The B737 on the other hand seems to have an elevator only marginally smaller than 1/4 of the full horizontal stabilizer including the elevator.
This must be a significant difference.

It seems like the A320, if we make that aircraft the comparison, because of its larger percentage elevater/stabilizer ratio to a much larger extent can rely on only the elevator in maintaining pitch control in demanding areas of the flight envelope, whereas the B737 much quicker runs out of elevater authority, and therefore Boeing has no option other than to use the very slow acting stabilizer trim function when controlling pitch in the most demanding areas of the flight envelope. And couple this with the likely worse naturable stability of the aircraft due to the very forward placement of the engines. This might be a reason why they couldnt make use of a redesign of the EFS acting on the yoke/elevator which would have been in my mind a much more quickly acting system. But ofc, such a system would also need a good software, and not the cludge MCAS seems to have been.

Try it on random people who havent seen it before. Just share it in the way they don't suspect something. You'll be surprised.

For the record, I failed it.

That MAY- repeat MAY be due to basic design for FBW versus ' cable ' control backup design for 737 and prior.

I note that seattle times article today mentions that initial stab movement was supposedly limited to .6 degrees for flight envelope and even for extreme csse. Flight test apparently showed/proved it needed to be 2.5 degrees for extreme conditions- due to extra lift from engine cowlings at high AOA- but somehow the documentation approved never got that number changed And/OR even thenit was not considered critical, etc
NO matter how one slices it- the ' fix' was FUBAR - and forgot that AOA sensors can easily be bent orhit by birds etc

Seattle Times on 737Max Crashes
 

Link to Seattle Times Article. Excellent journalism with much new information regarding the process that game us MCAS:

https://www.seattletimes.com/busines...ion-air-crash/

A single point of failure

Regulatory Capture.


A normailsation of deviance.
The incremental degradation of robust system design, implementation and testing continued unabated.

Always in the ear of management is the cost reduction mantra.

Some posters suggest case studies. Humanity never learns,
As it was before it will be again, usually as sufficient time elapses for the human ego to proudly boast, "this time is different"

That they found it was necessary with 2,5 degrees might indicate that the aircraft might be way off the required natural stability without the help of any system.

I'm not a pilot (well, only ex-PPL), but I am an engineer, working in safety-critical infrastructure. These two accidents are going to shake this industry. I know they have not yet been linked, but the gun is smoking.

Three massive issues stand out for me.

1. What has gone wrong at Boeing, that could allow a system to intervene, unknown to the flightdeck, but which had no redundancy on a vital input? Any systems analysis of this solution should have picked up this critical flaw...if it didn't, then the analysis (or analysors) was patently in error.
2. What has gone wrong at Boeing, that allowed a system to be designed, which used trim as a primary flight control? Correct me here if I'm wrong, but is trim not there to alleviate control forces once a flightpath has been established? Any system where trim is used in a primary manner is completely counterintuitive to flight crew. (maybe my understanding is wrong here, so happy to be corrected)
3. What has gone wrong at the FAA, that no-one caught this system? It seems they tried to devolve responsibility back to Boeing, but the FAA cannot do that...they are on the hook for this regulatory failure.

Corporate and regulatory culture is the problem here, and it stinks. I've always assumed Boeing were good guys, with a track record second to none. But something has gone wrong. And the FAA? I just find the whole thing staggering.

Pity the poor flightcrew...left with an airplane that had systems they didn't know about, without the necessary redundancy, and which was doing things they couldn't hope to assimilate at a crtical juncture in the flight.

The safest form of transport is facing a lot of questions just now.

Well, that actually forms part of the runaway stab trim checklist. If the cutout switches dont stop the trim then grab the wheel which is supposed to stop it.

Never tried it, don't want to.