Boeing 737 Max design error

On Monday, May 6, 2019 at 5:23:24 PM UTC-4, Lasse Langwadt Christensen wrot e:

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m wheel won't the electric trim be useless as well?

Normal Operations/Flight Controls, sub heading Manual Stabilizer trim:

to correct mis-trim. In extreme cases it may be necessary to aerodynamicall y relieve the air loads to allow manual trimming. Accelerate or decelerate towards the in-trim speed while attempting to trim manually."

Well, that answers one question. Apparently it's known and accepted that with enough trim and speed, you can't wind it by hand. Which makes the MCAS design all the more worse. A weathervane blowing in the wind can force the nose down hard, continually and if it's hard enough and you just follow the runaway trim procedure, you might not be able to recover period. Even worse, if the AOA is screwed, like the LA one was, reading 20 deg on the ground, when does MCAS try to kill you? Just as you're retracting the flaps, which means right after takeoff, at low altitude, where there may not be enough time to figure it out and recover.

t keep trimming for as long as it was powered

I think that's probably correct and it's also the more typical case. An intermittent short could do similar, but probably not every ten seconds and with such persistence. But if the common case is full runaway trim, then the fact that you may not be able to recover by hand isn't very good either. LEt's say it runs full amok, to the down limit, now the plane is diving, picking up speed, it takes X seconds to figure out what's going on and react. You turn it off and try to move the trim wheel. Can you?

Agreed. But "reminiscant" implies there are differences.

Indeed. In both cases.

Sorry for the mis-attribution.

What aircraft are or have you (i.e. snipped-for-privacy@optonline.net) been qualified to fly?

I don't know why you're repeating that.

There are two switches. They've been there since the year dot - they're not new to the 737 MAX. They're to be activated by the pilots in the case of a runaway trim. A runaway trim is where the trim is moved excessively for no valid reason. That's what was happening. The pilots should have use the switches. They didn't need to know about MCAS to do that.

If the switches are used, the MCAS cannot move the trim any more. The pilots can adjust the trim by moving the wheels by hand.

Sylvia.

One doesn't have to be qualified to fly anything to be allowed to comment. And if you look back at what I've posted, it's been absolutely right. Yet here you are questioning my qualifications? Why don't you question the qualification of the many posters here who have been WRONG.

One said that the AOAs only gave false readings in the air, not on the ground. That's wrong. Another said that when MCAS forces trim down, that there is nothing the pilots can do to override it. That's wrong. Another one said that without software the 737 Max stalls. Another one posted this:

When Boeing's execs heard an Ethiopian plane had crashed they were like "wtf? what are those monkeys doing running an airline with our planes, anyway? Well we'll just patiently explain to low IQ Americans that the reason it crashed is due to the even lower IQ of Africans. and well I guess we gotta pay something what's a good payout for a shithole country victim, like $25?"

Another one posted this:

"The Max has the rear of the engine at the front of the wing. That makes it stall easily."

Or this:

"My opinion is that such software should be written by pilots, not by spaced out no flying experience people."

And then some dummy posted this:

"This marketing push and corporate ethos thing is reminiscent of the VolksWagen diesel fiasco. "

And this LIE:

Other poster:

You: They were overridden by the MCAS.

That's an outright lie, as proven by the Lion Air flight the day before the crash. They had the same problem and the jump seat pilot told the other two dummies what to do, follow the runaway trim procedure. Not only did it not crash, it flew on to it's destination using manual trim. What did they do? Turn off the two switches for the trim motor and trim MANUALLY. Geez.

Or this gem:

"It was far more than "trim".

That's another lie. All MCAS can do is apply nose down trim. If you have proof otherwise, present it to us, Mr. "Expert".

You're just sore because you think you know it all and can't deal with someone who has the FACTS.

DC-9s were OK planes. The Fairchild F-27 (Ozark Airlines, AKA Ox-Cart) was a real bucket of bolts. They unbalanced the props so the wings flapped harder to generate lift. Then there was the Short SD3-30 (Command Airways, AKA Kamikaze Airlines). The doors fit so loosely that you could see daylight around them. When it rained, water came in through the door.

There is some Boeing documentation on this. Mentour Pilot discusses this in one of his videos - possibly this one.

Certainly the load on the trim jackscrew increases as the aircraft is further out of trim, and this can reach the level where the pilots are not strong enough to turn the trim wheels. Boeing suggest briefly unloading the control column to allow the trim wheels to be turned, and then loading the control column again to recover the flight path, and do this repeatedly, until the situation improves.

Of course, to get into that position the pilots have to fail to address the deteriorating trim situation.

Sylvia.

This is incorrect.

Not during those 30 seconds perhaps, but wind shear can change things in an instant.

Swing a $1 MEMS chip round your head. Which angular position is which now? An aircraft in flight is essentially a free body with only gravity as a reference, which can be confused by any other sort of acceleration force.

Angle-of-attack vane sensors actually measure the angle of passage of air around the airframe relative to the inclination of the airframe and consequently offer information which can't reliably be measured or calculated otherwise, which is precisely why they use fragile external sensors to measure it.

Regrettably not, but after all this /is/ usenet.

No, it hasn't.

You haven't been paying attention!

Your descriptions of aerodynamics and how aircraft fly (and fail to fly) have been "novel". Since that's central to the points you have been asserting very confidently, it is worth confirming and assessing your competence in the topic.

It's worse than that. An aircraft in flight does not have gravity as a reference, what keeps you in your seat is the reaction to lift, and lift is perpendicular to the wings, not the ground.

On a sunny day (Mon, 6 May 2019 21:52:18 -0700) it happened Riley Angel wrote in :

Most toy drones, including mine a bit less toy now, use these chips and keep perfectly horizontal, so know about attitude. Calibrated before takeoff, like an pressure based altimeter.

Using those for absolute position like inertia based navigation is harder, I have published some drift test about that in an other group, then some university did a lot better some years ago., but that is not the issue here. The issue is seeing the nose already pointing down, if so do not continue pointing it more down.

Mechanical sensors exposed to the plane's outside are vulnerable to many things, from birds to ice to what have you. redundancy is then a must. As somebody already pointed out the pitot tube issue has also killed many many people, not so long ago a plane fell out of the sky here due to that, wrong airspeed. Some years ago I was experimenting here with ultrasonic air speed measurements (wind speed and direction), more just for fun, a second system using a different measurement system could make things safer I'd think.

Almost look like things are stuck... FAA needs an overhaul and leave beaten paths,

snipped-for-privacy@gmail.com wrote in news: snipped-for-privacy@googlegroups.com:

Max

This group does not give any friends away. They must be earned. And then too, the very definition of the word is askew here.

So do not bother to ask for a friend, because they are rarely available by request.

snipped-for-privacy@gmail.com wrote in news: snipped-for-privacy@googlegroups.com:

Asking for an alien confirmation?

In what way is it incorrect? His description is a fairly succinct explanation of the problem that MCAS was intended to address. Namely that the physically bigger engines and shifted centre of gravity made the plane tend towards an AoA stall condition if left to its own devices. (but only in some fairly rare edge cases)

The AoA sensor and MCAS was meant to intervene before this happened.

In reality if the AoA sensor went bad MCAS would force the plane nose down into a steep power dive and generate non-sensical stall warnings. Worse it was able to reset and do it again and again making far more significant adjustments to the trim than implied by its specification.

FAA were clearly asleep on the job - their responsibility to do an independent check that Boeing safety system engineering was sound.

Jan Panteltje wrote in news:qapdk2$flj$ snipped-for-privacy@dont-email.me:

'and it had no redundancy' which the dopey tradertard4 dipshit will use to claim he is right.

I said software a long time ago, like the day after it happened.

It was, however there are notable hardware issues which I would also have done differently.

IOW software change alone could fix it, however there would still be a chance of the manipulator getting at the end of its travel and requiring manual reset to the zero trim point. The entire idea has striong issues where a pilot needs to know how and when a detachment of this system would be needed to restore pilot control in a situation where the system was malfucntioning.

They likely needed to install a method to detach the hydraulic arm completely from the elevator (tail) to 'give back' pilot control if 'requested'. These were not trim tabs, this thing moves the entire elevator, a pilot's nightmare, IMO.

snipped-for-privacy@optonline.net wrote in news: snipped-for-privacy@googlegroups.com:

The problem is that when finally turned off, the movement MCAS ALREADY DID perform placed the tail in an unstable position, and required a SLOW, MANUAL, PILOT INITIATED RETURN.

There needs to be a system that once deativated, allow full IMMEDIATE restore of pilot control, WITHOUT a SLOW, MANUAL EFFECTOR POSITION MOVEMENT REQIUISITE.