Lion Air crash: Jakarta Boeing 737 'had prior instrument error'

[KL27x]

fascinating, everybody want to learn about aeroplane. iirc a diagram, pitch is angle of fuselage to motion vector and AoA is wing cross section (or effective horizontal line? damned terminology) to relative air motion angle the wing is attacking.

Damnation. The pitch is relative to the horizon/earth; it is not relative to the current vector of the plane. Look at the picture Odgen originally posted. See the dotted line? That's the plane's vector; IOW, that is the direction the plane is actually travelling. The angle of the plane (or wing, or the average angle of the wing) relative to this dotted line is the AOA, not the pitch. Pitch is relative to the earth/horizon.

i guess yeah, its possible cruising at 0 degree pitch (fuselage angle)

Of course it's possible some planes can do this. It's also possible for a plane (not a loaded 737, apparently) to fly level with a zero degree AOA of the wings, even. The wing creates lift by the curvature of the top surface. So it doesn't necessarily need to be angled up for a plane to fly level.

[SkyMaster]

OK, so:
1. Angle between the longitudinal axis of the aircraft and earth (irrespective of direction of travel): is called Pitch
2. Angle between the longitudinal axis of the aircraft and the velocity of the aircraft through the air: is called AOA (assuming we choose the "another choice" in the Wikipedia definition); and needn't be positive in straight and level flight (especially at high speed)
3. Angle between root chord of the wing and velocity of the aircraft through the air: is also called AOA (assuming the chord line definition is used).

In short, let's stop arguing over an ill-defined term like AOA. A wing designer probably has definition 3 in mind, while a pilot maybe probably has definition 2 in mind.

You are correct with: A wing designer probably has definition 3 in mind, while a pilot maybe probably has definition 2 in mind.

Once in flight, the wing angle of incidence becomes irrelevant, to the pilots.

 

[Mechatrommer]

The wing creates lift by the curvature of the top surface. So it doesn't necessarily need to be angled up for a plane to fly level.

yes Bernoulli's principle, but i saw youtube sometime ago that this is a myth. aerofoil only contributes miniscule to the lift esp on a big fat plane, the major contributer is wing angle of attack. i have some belief to this, a paper craft doesnt need aerofoil to lift, fighter jet will have shallower (thinner) wing profile to cut air more effectively at supersonic.

[SkyMaster]

What exactly you are implying?

I'm very clearly stating a fact. You don't need to understand how a plane flies to fly it.

 

Having extensive experience as a Flight Instructor, I strongly disagree with your statement.

A pilot who lack understanding of how a plane flies; is an accident waiting to happen.

This is true in a small general aviation airplane, and this is true in a large airliner.

 

[KL27x]

^And yet this is not the case. Some pilots might get enough answers correct on a multiple choice test, but they don't understand it and never will. And yet they can fly us around more safely, in all likelihood, than most of the guys that designed the airplane.

The world is too complicated for the average person to understand beyond some small scope of their experience. This is purportedly part of the reason MCAS was not disclosed at first.

[SkyMaster]

The wing creates lift by the curvature of the top surface. So it doesn't necessarily need to be angled up for a plane to fly level.

yes Bernoulli's principle, but i saw youtube sometime ago that this is a myth. aerofoil only contributes miniscule to the lift esp on a big fat plane, the major contributer is wing angle of attack. i have some belief to this, a paper craft doesnt need aerofoil to lift, fighter jet will have shallower (thinner) wing profile to cut air more effectively at supersonic.

Some aircraft have Symmetric airfoils. The F-104 wing profile is pretty close to a flat plate and a sharp leading edge.

 

[KL27x]

^Not surprising that it's a supersonic fighter jet. At super high speeds and with mega thrust to weight ratio, it doesn't need lift. Plus, how cool is it to be able to fly upside down with almost as much efficiency as right-side up?

If you tried to do that on a passenger jet, the plane would have to use to much AOA at subsonic cruising speeds and produce too much drag and burn too much fuel.

[SkyMaster]

^And yet this is not the case. Some pilots might get enough answers correct on a multiple choice test, but they don't understand it and never will. And yet they can fly us around more safely, in all likelihood, than most of the guys that designed the airplane.

I never saw a multiple choice test during a flight test or checkride.

 

[Brumby]

What exactly you are implying?

I'm very clearly stating a fact. You don't need to understand how a plane flies to fly it.

 

Having extensive experience as a Flight Instructor, I strongly disagree with your statement.

A pilot who lack understanding of how a plane flies; is an accident waiting to happen.

This is true in a small general aviation airplane, and this is true in a large airliner.

 

I'm not a pilot, but THIS gets a big thumbs up from me!

^And yet this is not the case. Some pilots might get enough answers correct on a multiple choice test, but they don't understand it and never will. And yet they can fly us around more safely, in all likelihood, than most of the guys that designed the airplane.

This is a poor statement, IMHO.

Kelly Johnson did not need to know how to fly the SR71 in order to design it - and Brian Shul did not need to know how to design the SR71 in order to fly it - but they could have a discussion about the flight characteristics.

[SkyMaster]

The world is too complicated for the average person to understand beyond some small scope of their experience. This is purportedly part of the reason MCAS was not disclosed at first.

A pilot is not an average person.

 

[Brumby]

^And yet this is not the case. Some pilots might get enough answers correct on a multiple choice test, but they don't understand it and never will. And yet they can fly us around more safely, in all likelihood, than most of the guys that designed the airplane.

I never saw a multiple choice test during a flight test or checkride.

 

... and I would hope nobody ever considers this.

Multiple choice is an extremely weak form of testing.  In some cases, getting the correct answer can come from eliminating the wrong ones.  This is stupid.  I have this same concern for our "knowledge" driving test you need to take before getting your learner's permit.  If you see a sign on the road, you need to know what it means because there won't be a list of 4 options hanging underneath it from which you choose.

This is even more critical when you're up in the sky.


Multiple choice testing is done simply because it is far easier to mark.

[Brumby]

The world is too complicated for the average person to understand beyond some small scope of their experience. This is purportedly part of the reason MCAS was not disclosed at first.

A pilot is not an average person.

 

If I'm ever in an aircraft where the pilot is an "average person", I'm going to tell them to move over!

[KL27x]

Umm, I am certain many pilots are average people. If an average person with the proper training could not safely fly a commercial passenger jet, then I wouldn't get on one. I'm not talking landing on an aircraft carrier at night in high wind. If commercial passenger pilots require some superhuman skills and in depth knowledge to be safe, then these planes are not safe enough, yet.

When pilots need to score 95% percentile on the LSAT and have 130+ IQ, then I'll change my mind. Flight training contains some basic practical aerodynamics education, at best. And without basic understanding of newtonian physics it is just superficial information. 99% of the population doesn't understand basic newtonian physics.

If anything, I want my pilot to be abnormally reliable and responsible. Doesn't drink, do drugs, doesn't stay out all night. I don't care if he has an IQ of 90 or doesn't understand physics and aerodynamics as long as he has been trained and demonstrates proficiency in his training and flying. It is way more important to me that he shows up ready and prepared to do his job, and that he takes this responsibility seriously.

A good jockey doesn't need to be a biologist or an expert in husbandry.

Kelly Johnson did not need to know how to fly the SR71 in order to design it - and Brian Shul did not need to know how to design the SR71 in order to fly it - but they could have a discussion about the flight characteristics.

How many commercial pilots have this kind of relationship with the designer of the plane and can make their own tweaks to the plane during the development? Zero. Even if this was the case, it still doesn't change my point. The designer of the plane can't necessarily fly it for squat. The pilot doesn't necessarily have to understand how it flies for squat. 

[SkyMaster]

If anything, I want my pilot to be abnormally reliable and responsible. Doesn't drink, do drugs, doesn't stay out all night. I don't care if he has an IQ of 90 or doesn't understand physics and aerodynamics as long as he has been trained and demonstrates proficiency in his training and flying. It is way more important to me that he shows up ready and prepared to do his job, and that he takes this responsibility seriously.

How many pilots do you employ?

Or, are you implying that when you fly as a passenger, you do a background check on your pilot, and you get to choose your pilot?

 

[tautech]

Umm, I am certain many pilots are average people. If an average person with the proper training could not safely fly a commercial passenger jet, then I wouldn't get on one. I'm not talking landing on an aircraft carrier at night in high wind. If commercial passenger pilots require some superhuman skills and in depth knowledge to be safe, then these planes are not safe enough, yet.

When pilots need to score 95% percentile on the LSAT and have 130+ IQ, then I'll change my mind. Flight training contains some basic practical aerodynamics education, at best. And without basic understanding of newtonian physics it is just superficial information. 99% of the population doesn't understand basic newtonian physics.

If anything, I want my pilot to be abnormally reliable and responsible. Doesn't drink, do drugs, doesn't stay out all night. I don't care if he has an IQ of 90 or doesn't understand physics and aerodynamics as long as he has been trained and demonstrates proficiency in his training and flying. It is way more important to me that he shows up ready and prepared to do his job, and that he takes this responsibility seriously.

Having watched my daughter progress through her PPL, IFR, Instructors rating, CPL and into then commercial aviation with mates dropping out from courses I can assure you ppls that acquire even a co-pilots position are much more than the average Joe or Jill. Only the cream rises to the top and that's now it must be in commercial aviation.
Even the first steps down this road require knowledge and understanding of the plane's mechanics, principles of flight, navigation and one that many struggle with; Meteorology.

[Mechatrommer]

well not an average person maybe, but a chick, maybe she can land an airplane (which is the hardest part i figured during simulation)... but dont do this at home please only if all options are exhausted, for example a pilot or an "above than average" person is not currently available ATM (use your imagination)...

[Brumby]

Whoa.

Certainly landing is perhaps the single most difficult thing in flying an aircraft - but there are a lot of other things going on - and a lot of preparation for even the most straightforward of flights.  Navigation alone is crucial - and while there are a lot of electronic systems to manage that, they still have to be set up correctly - and if they fail, the pilot will need to know how to work without them.

This is not to mention all the possible things that can go wrong!  I could go on and on with speculation on this subject alone and not cover anywhere near the list that an instructor could.

In these cases, your pilot needs to be very aware of the physics of his aircraft, the systems it carries, the options available and a whole bucketload of other things and be able to work their way through an emergency situation with a clear level head.  It's not as if you can just coast to the shoulder of the road if something goes wrong.

Your "average person" is not going to have a hope in hell.

[Nusa]

Instruction on the principles of aerodynamics, among other things, is part of the requirements to receive a pilots license. Even for recreational pilots.

On the subject of things that can go wrong, read this:
https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/airplane_handbook/media/06_afh_ch4.pdf

That PDF states the definition of "Angle of Attack" as defined for instructional and testing purposes. Pilots will be aware of that definition, even if the general public wants to argue about it.

[KL27x]

The angle of attack (AOA) is the angle at which the chord of
the wing meets the relative wind. The chord is a straight line
from the leading edge to the trailing edge. At low angles of
attack, the airflow over the top of the wing flows smoothly
and produces lift with a relatively small amount of drag. As

And if by extension a pilot can't extrapolate more than one way to state this... that the nose-tail axis of the plane is essentially the same as orientation of the chord of the wing, and in fact if there is any deviation between the chord of the wing and the axis of the plane it is completely irrelevent...

I'm sure that doesn't disqualify them from flying a plane despite not being a sharpest tool in the shed.

You'd have to be especially dimwitted to be disqualified for reasons of not being able to pass a government mandated terminology regurgitation exam. I imagine most of the actual weeding out is for professionalism. Character, personality, work ethic, reliability, temperament, maturity. And then like any other profession, the politics. Additionally for a pilot, having a certain confidence-inspiring look don't hurt. If you check all those boxes, then oh, yeah. Let's see if you can actually fly the plane. Gawd let's hope so, because the rest looks perfect.

I don't want Albert Einstein to fly my plane. I want a professional pilot weeded out for his professionalism and ability to fly a plane.

[floobydust]

Hello floobydust,

The Captain side AOA indicator is connected to the left side AOA vane, and the First Officier side AOA indicator is connected to the right side AOA vane. This still the case if there is a "AOA disagree".

The image from your message https://www.eevblog.com/forum/chat/lion-air-crash-jakarta-boeing-737-had-prior-instrument-error/msg2308272/#msg2308272 is showing the green and red zones, but they are not highly visible.

Two AoA sensors - you have a redundant system with no check for agreement, an original MCAS engineering error.
Now with Boeing's "fix", it seems there are two gauges (Captain, First Officer) and the fact that human beings have to have a discussion between them to see which sensor is out, or if both are out, what to depend upon.
It's playing the same song- redundant systems are safer but not so if one sensor failure gives doubt to the other's integrity. Now humans are involved to confirm the old adage "with two clocks, one can never know the correct time". I don't see the added gauges being useful, they add confusion as implemented.

[tautech]

You'd have to be especially dimwitted to be disqualified for reasons of not being able to pass a government mandated terminology regurgitation exam. I imagine most of the actual weeding out is for professionalism. Character, personality, work ethic, reliability, temperament, maturity. And then like any other profession, the politics. Additionally for a pilot, having a certain confidence-inspiring look don't hurt. If you check all those boxes, then oh, yeah. Let's see if you can actually fly the plane. Gawd let's hope so, because the rest looks perfect.

Yep all that ^.
But as you say one first has to be able to demonstrate appropriate flying skills too.

My daughter as a instructor spent a couple of years at FTA (Flight Training Adelaide) where she had to check fly the successful applicants for a few big airlines and while these guys and gals might have met their local examination requirements some couldn't make the grade when it came to the standards an international airline requires. So while you might have the goods to meet a CFL it comes down to real ability not some bit of paper.

I've had the pleasure over some decades to know a good few NZ international pilots and without exception they are very humble of their abilities.

[BradC]

Your "average person" is not going to have a hope in hell.

I actually tried this last year for a bit of a laugh. I went up in a Cessna with an instructor to see what it was about. Having zero experience at the controls and basic understanding of the physics and mechanics involved.
The instructor talked me through getting it off the ground and after a bit of time "getting a feel for the machine" the instructor commented I was a bit more "measured" than the usual "joy flight muppets" (ie I didn't want to try and stand it on its wing or do a loop) and asked me if I'd like to try the approach and landing. I could get the thing off the ground, I got it out and around the pattern, did a lap of rotto, managed all the relevant things he wanted me to manage and made it do everything he asked me to make it do.

Then came the landing. So calm as you like I lined up on a long final, and he talked me down. A bit of a crosswind, but nothing awkward. It got *busy*. Really busy. So much so that a couple of hundred feet off the ground I asked him to take control and do a go-around. So yeah, that was a little buzz box with about 4 controls to manage, I knew the theory of what I should be doing *and* I had an instructor in my ear *telling* me what I needed to be doing and it still got away from me. I've since done some landings in a 737 sim, but without the risk of damage and a crapload more inertia it's a bit more casual. Nobody minds a bounce in a sim.

I've also been lucky enough to do a lot of jumpseat approaches in bigger birds over the years, but frankly I *want* the people up the front to know not only how to competently fly the thing, but to know enough about it to make a reasoned attempt at working around any issues when things turn to porridge.

[Nusa]

Even knowing what to do is not entirely enough. One has to get used to the individual planes as well. I started out in gliders, and had done plenty of solo flights in the high-wing two-place trainer. Then came the day I was allowed to fly the low-wing single-seat. I ended up too high on final approach to correct with a slip and spoilers and was forced to do a 360 to lose altitude. That was embarrassing enough, but then shortly after I put my wheel on the grass strip, I managed to ground-loop it when I let a wing drop too much. No damage, not even to the grass, but one has absolutely no control at that point and just has to ride it out. That was 45 years ago and one of those days I'll never forget.

[Hyper_Spectral]

Wow, there is A LOT of armchair pilots in this thread 

[floobydust]

Boeing's response- blaming the pilots, not their shit MCAS software and AoA sensors, is the problem.
Blaming the victim minimizes the criminal act.
Even if it was the crew's error, no (undocumented) system should be designed to rely on "a memory item" to stop a fatal dive.