Ethiopian airliner down in Africa

[Azgalor]

Originally Posted by megapete

I also wonder if the forward position of the engines, which gives a pitch up moment at high angles of attack, and led to the addiction of MCAS, could possibly give a pitch down moment at low angles of attack?

How the engines do that? What is supposed to be a problem? I expected that power and placement of engines creates this pitch up moment. Is it something aerodynamics related?

[megapete]

Originally Posted by Azgalor

How the engines do that? What is supposed to be a problem? I expected that power and placement of engines creates this pitch up moment. Is it something aerodynamics related?

Yes its aerodynamic - my understanding ,from reading the whole thread, is that the engine nacelles being in front of the C of G exert aerodynamic forces - a positive angle of attack gives a pitch up moment - and subsequent reduction of stick back pressure approaching the stall - hence MCAS. I was just speculating if a low angle of attack would produce a nose down moment as the engines are presumably mounted to be zero A of A when the wing is at cruise A of A.

[dozing4dollars]

Question: does the 737Max have a Q limiter on the elevator deflection?

[FCeng84]

Originally Posted by Azgalor

How the engines do that? What is supposed to be a problem? I expected that power and placement of engines creates this pitch up moment. Is it something aerodynamics related?

This is a very large thread, but if you want to know what is going on here you need to read from the beginning or at least skim through. Your question has been covered in numerous posts. You are welcome to search on my user name to see what I have contributed, but I suggest you read other's entries as well.

[FCeng84]

Originally Posted by dozing4dollars

Question: does the 737Max have a Q limiter on the elevator deflection?

Need you to describe what you mean by "Q limiter".

[gearlever]

Dynamic pressure?

[FCeng84]

Originally Posted by gearlever

Dynamic pressure?

That's what I suspect, but I want to have dozing expand on the question a bit before answering.

[dozing4dollars]

Question: at what angle between stabilizer and elevator does the tail plane stall?

[Chronus]

I wondered why Boeing named their newest version of the successful 737 MAX. So I did a quick internet search and here is what came up:
https://www.airlinereporter.com/2011...s-the-737-max/

Here is an extract from the article:

"Yes, I understand the ideas behind Boeing choosing this name, but it doesn’t mean the name works. During the press conference announcing the re-engined 737, Nicole Piasecki explained why Boeing chose the MAX name. “We wanted the name to capture how exceptional the 737 is not only to in terms of its performance but we wanted it to be able to differentiate the 7, 8 and 9. We wanted to make sure the name was easily identifiable from 4-year olds up to 90-year olds and we wanted to make sure that it represented the best that it will truly be… We thought about how do you convey superiority, the best, the gold standard in single-aisle airplanes. And how do you come up with a name to describe already a great airplane. We wanted to make sure that it talked about what it was going bring to the industry in terms of maximum benefit, maximum competitive advantage for our customers, maximum value and absolute maximum in what an airplane could deliver to our customers. So we came up with something that fit that and we will be calling this airplane the 737 MAX.”

I do wonder whether after all the who ha is all over the air traveler will be asking whether it is a MAX they are about to board or even worse check before they buy the ticket.

[vlieger]

737 MAX scandal: Boeing putting profits before safety

https://www.marxist.com/737-max-scan...ore-safety.htm

Short-sightedness and incompetence

A similar process of “soft corruption” and conflict of interest can be seen in the financial industry in various countries across the world, made worse by deregulation. The Airline Deregulation Act of 1978 started a process of removing government controls over the airlines and manufacturers in the USA. This was done to encourage competition and lower the ticket prices, but the end result has been the monopolisation of air travel to the point where four major carriers control 80 percent of US air traffic. Tickets did become cheaper but travelling by plane has generally become a miserable experience worldwide and the workforce – from pilots and cabin crew to dispatchers, baggage handlers and office workers – is more exploited, underpaid and demoralised than ever.
Combine this with the majority of establishment politicians sitting on the boards of private companies and you have a clear recipe for disaster. It is a cosy club where everybody looks after each other: regulators, manufacturers and politicians. Obviously, for any airline or manufacturer, any serious incident or accident is bad publicity and is to be avoided. The general level of safety in aviation since the 1980s has been relatively good, and numerically speaking, flying remains the safest method of transportation. Under capitalism, however, with profit as the primary goal, there will be a never-ending battle of short-term expense versus long-term safety, where the latter finishes a long way behind.

This short-term thinking ties in with the increasing short-sightedness and sheer incompetence of the political elite worldwide. In the UK we have the Brexit circus, in the USA we have Trump. The Twitter president was quick last week to send yet another bizarre tweet saying that “airplanes are becoming far too complex to fly” and that he doesn’t want “Albert Einstein to be his pilot”. This comes from a man who doesn’t know how to close an umbrella upon entering the presidential 747 and who last year nominated his own pilot, John Dunkin — the man who flew Trump planes, not Air Force One — to head the FAA. As the Financial Times put it:

“When the Senate laughed him off as unqualified to lead an $18bn agency, Mr Trump failed to come up with a new name. The FAA has been flying without a pilot, so to speak, for more than a year. Little surprise America’s partners have lost trust in its direction.” (March 13, 2019)

Yet, like a broken clock that is right twice a day, Trump in this instance has a point, even if we can’t suspect him of having any real level of comprehension of the matter at hand.

[abdunbar]

Originally Posted by canyonblue737

Yes, clearly different than a runway and yes, the column cutout doesn't work with MCAS. Yes the trim wheel moving, even in manual flight, even when not trimming with the yoke switch is normal in a 737. That said you would think in 7-12 minutes of watching the nose get heavier and heavier and the trim moving downward on occasion on its own you would kill the trim with the stab cutout switches. I totally get the anger at Boeing but experienced 737 pilots should be able to figure this out, in particular with a bit of time, and after the Lion Air accident and the required reading of the MCAS system and its failure mode you would think any 737 MAX pilot would be able to figure this out very, very quickly let alone with time. Lots of blame to go around here in these accidents, starts with Boeing but as usual it ends in the point end of the jet.

Exactly!! There is a large range in pilot skill level and dedication. The most dedicated group I personally flew with was Japanese pilots at a small airline based out of Tokyo. They knew the aircraft systems backwards and forwards. They had their own study sessions and they also kept records of the expat Captains qwerks and briefed each other on those also. Was not unusual to pick up one of these young men who had a total flight time under 300 hours. And yes it showed but they matured rapidly and became very skilled pilots quickly.

but back to the question at hand.... Yes, there will be enough blame to go around and I really like Boeing and am sad that they let this happen to them. I have sympathy for people who work for unenlightened airline managements that let politics and favoritism trump safe operating decisions. There are people who are a danger to themselves and others and truly do not know it. I hope that on the positive side, this accident has drawn enough attention that ALL are watching and learning.

If the 737 MAX or any other aircraft can be flown out a corner of the envelope from which recovery is not possible we need to know about it and fix it.

BTW, my personal standard for releasing a pilot to line flying was simple. I imagined my family in the back and had him fly the entire let down and approach without the autopilot or auto throttle Very few had much problem with this. We trained for this, everyone was familiar with the power and attitude required for every common configuration.

[FCeng84]

Originally Posted by dozing4dollars

Question: at what angle between stabilizer and elevator does the tail plane stall?

Depends on horizontal stabilizer position, AOA, and airspeed. With stabilizer in trimed position elevator retains effective control through its full range of roughly +/-30 degrees up to about 250 knots.

[abdunbar]

Originally Posted by dozing4dollars

Question: at what angle between stabilizer and elevator does the tail plane stall?

well, as you stated before, that depends. the angle would be pretty small at Mach 1 . ;-)

[jagema]

Originally Posted by Azgalor

How the engines do that? What is supposed to be a problem? I expected that power and placement of engines creates this pitch up moment. Is it something aerodynamics related?

Underwing-mounted engines, being under the center of gravity, create a pitch-up moment when adding thrust. Pitch-down when reducing thrust. Easy to picture: letter T. Push the lower end of the vertical line, pushing force being the thrust vector forward. The junction of the T (where vertical meets horizontal axis) being the CG - The whole thing swings clockwise (nose up).

[Chesty Morgan]

Originally Posted by jagema

Underwing-mounted engines, being under the center of gravity, create a pitch-up moment when adding thrust. Pitch-down when reducing thrust. Easy to picture: letter T. Push the lower end of the vertical line, that'd be the thrust vector. The junction of the T (where vertical meets horizontal axis) being the CG, it'll swing the whole thing clockwise.

But that isn't what's happening with the MAX .

[FCeng84]

Originally Posted by jagema

Underwing-mounted engines, being under the center of gravity, create a pitch-up moment when adding thrust. Pitch-down when reducing thrust. Easy to picture: letter T. Push the lower end of the vertical line, pushing force being the thrust vector forward. The junction of the T (where vertical meets horizontal axis) being the CG - The whole thing swings clockwise (nose up).

Need for MCAS is not related the thrust pitch coupling. Read previous thread entries to understand and catch up with the discussion.

[flyingchanges]

Originally Posted by Chesty Morgan

Ever flown a 737?

Yep, about 6,000 hours...

[dozing4dollars]

Originally Posted by FCeng84

Need you to describe what you mean by "Q limiter".

In other aircraft the elevator has a dynamic limiter. The Q limiter. Q is the airodynamic force. This is a combination of airspeed and density altitude. The same as the force sensed by the pitot tube. The purpose of the Q limiter is to limit the maximum elevator angle. At lower Q the pilot has full authority over the elevator but as Q increases, the angle is limited.

In ithe scenario where an aircraft is low and fast the elevator deflection available is limited. It should be noted that elevator deflection is based on deflection from the trimmed position of the stabilizer.

[VFR Only Please]

TacomaSailor, I don't know the answers to your questions, and doubt anyone here Knows For Sure.

There is something in the US called the Aviation Safety Reporting System. It's run by NASA, precisely to keep it our of the FAA's hands. It's part confessional, part wailing wall for pilots. You can air your troubles, being as discreet about your personal identity as you wish.

Anyway, there have been a number of complaints about the MAX. (One pilot, after Jakarta: “I am left to wonder: what else don’t I know?”) And these include the autothrottles. Perhaps those far more knowledgeable than I will hoot at this, but it does add a dimension to the speculation mix.

[abdunbar]

Originally Posted by vlieger

https://www.marxist.com/737-max-scan...ore-safety.htm

Short-sightedness and incompetence

A similar process of “soft corruption” and conflict of interest can be seen in the financial industry in various countries across the world, made worse by deregulation. The Airline Deregulation Act of 1978 started a process of removing government controls over the airlines and manufacturers in the USA. This was done to encourage competition and lower the ticket prices, but the end result has been the monopolisation of air travel to the point where four major carriers control 80 percent of US air traffic. Tickets did become cheaper but travelling by plane has generally become a miserable experience worldwide and the workforce – from pilots and cabin crew to dispatchers, baggage handlers and office workers – is more exploited, underpaid and demoralised than ever.
Combine this with the majority of establishment politicians sitting on the boards of private companies and you have a clear recipe for disaster. It is a cosy club where everybody looks after each other: regulators, manufacturers and politicians. Obviously, for any airline or manufacturer, any serious incident or accident is bad publicity and is to be avoided. The general level of safety in aviation since the 1980s has been relatively good, and numerically speaking, flying remains the safest method of transportation. Under capitalism, however, with profit as the primary goal, there will be a never-ending battle of short-term expense versus long-term safety, where the latter finishes a long way behind.

This short-term thinking ties in with the increasing short-sightedness and sheer incompetence of the political elite worldwide. In the UK we have the Brexit circus, in the USA we have Trump. The Twitter president was quick last week to send yet another bizarre tweet saying that “airplanes are becoming far too complex to fly” and that he doesn’t want “Albert Einstein to be his pilot”. This comes from a man who doesn’t know how to close an umbrella upon entering the presidential 747 and who last year nominated his own pilot, John Dunkin — the man who flew Trump planes, not Air Force One — to head the FAA. As the Financial Times put it:



Yet, like a broken clock that is right twice a day, Trump in this instance has a point, even if we can’t suspect him of having any real level of comprehension of the matter at hand.

I agree with a lot of your post but while is popular here and abroad to bring Trump into everything I do not think he has much to do with the current state of affairs at the FAA. The cozy regulator/industry relationship has been long in the making and the problem is often noted. The "dual mandate" to oversee aviation safety and promote air commerce was ended by Congress in 1996 but top civil service jobs are often political. Influence can be subtle. I remember a situation at a large domestic airline. The airlines fleet manager was disturbed at the number of pilots needing more simulator time in order to satisfactorily complete the steep turn demonstration. He decided that he would just take it out of the syllabus. He was over ruled by the FAA model manager for that aircraft at that airline. He took the matter over her head and her boss agreed with him that for what ever reasoning, steep turns were not important and could be deleted from the syllabus/check rides.