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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 18th Mar 2019, 19:59
  #1981 (permalink)  
 
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Originally Posted by dozing4dollars View Post
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.
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Old 18th Mar 2019, 20:01
  #1982 (permalink)  
 
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Originally Posted by dozing4dollars View Post
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 . ;-)
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Old 18th Mar 2019, 20:04
  #1983 (permalink)  
 
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Originally Posted by Azgalor View Post
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).
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Old 18th Mar 2019, 20:07
  #1984 (permalink)  
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Originally Posted by jagema View Post
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 .

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Old 18th Mar 2019, 20:08
  #1985 (permalink)  
 
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Originally Posted by jagema View Post
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.
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Old 18th Mar 2019, 20:10
  #1986 (permalink)  
 
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Originally Posted by Chesty Morgan View Post
Ever flown a 737?
Yep, about 6,000 hours...
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Old 18th Mar 2019, 20:11
  #1987 (permalink)  
 
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Originally Posted by FCeng84 View Post
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.


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Old 18th Mar 2019, 20:11
  #1988 (permalink)  
 
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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.
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Old 18th Mar 2019, 20:17
  #1989 (permalink)  
 
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Originally Posted by vlieger View Post

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.
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Old 18th Mar 2019, 20:17
  #1990 (permalink)  
 
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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 is the business school graduate's mission: Profit. Either grow revenue or cut cost.

Until the Lion Air crash, no 737 MAX pilot had ever heard of this completely new MCAS system, which was not documented anywhere, never mind trained for in the simulator. In fact, this was one of the main selling points that helped Boeing secure the 5,000 orders for the 737 MAX: no expensive separate type rating – on average a 5-6 week training involving full-motion simulators, which are very expensive to run – needed for your existing 737 pilots, who can keep making your company money.
The roots of this crisis can be found in a major change the agency instituted in its regulatory responsibility in 2005. Rather than naming and supervising its own ‘designated airworthiness representatives,’ the agency decided to allow Boeing and other manufacturers who qualified under the revised procedures to select their own employees to certify the safety of their aircraft. In justifying this change, the agency said at the time that it would save the aviation industry about $25 billion from 2006 to 2015. Therefore, the manufacturer is providing safety oversight of itself. This is a worrying move toward industry self-certification.
A relationship that is confused. Self regulation and budgetary pressure.
Regulatory capture.

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.
In the centuries old battle of profit above all else, safety can only ever come a distant second.

The reputational damage to the FAA and indeed Boeing is substantial.

Whatever the correlated factors between the two accidents, MCAS is the symptom. The problem has its genesis in three elements:
  1. The focus on infinite profit growth with infinite cost reduction (a product of business school) MBA teaching
  2. Regulatory Capture
  3. Soft corruption
There is no need for a case study. This is one of the oldest themes and the arrogance of humanity condemns it to repeat over and over.
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Old 18th Mar 2019, 20:19
  #1991 (permalink)  
 
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How many of you know what the stab trim range is in normal flight on your type. Might be a good time to pay attention to where your most powerful flight control spends most of its time. I know for our ops, the 800NG lives between 5 and 6 just about all of the time.

If the jet is doing something you don't want with a flight control, do something about it. I would call it a runaway, you can call it what you want. Yes, the trim moves a lot when hand flying, but it never moves enough to need substantial column input to counter it.
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Old 18th Mar 2019, 20:29
  #1992 (permalink)  
 
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Originally Posted by dozing4dollars View Post


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.
Got it, thanks for expanding. What I was wanting to know was if you were pointing to an explicit command limit within the control system that would keep from asking more of the elevator actuators than they can deliver vs. a system that asks for everything that is available and takes what it gets when elevator actuators are driven with full available hydraulic pressure. I am familiar with both types of systems. In the case of the 737 the limit is hydro-mechanical in that the elevator actuator control valves are wide open but the elevator hinge moment is more than the actuators can deliver so the surface ends up at a less than full travel position. I am familiar with this being referred to as either "blowdown" or "blowback". Note that if you are flying with high enough dynamic pressure for that to be the limiting factor and you command full elevator with full column and you hold that column and you speed up, the elevator deflection will decrease as dynamic pressure increases. With reference to Star Trek, that's when Scotty says "She's give'n you all there is, there just isn't any more to be had." Glad to provide this answer once I was certain of your question.

Last edited by FCeng84; 18th Mar 2019 at 20:36. Reason: typo
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Old 18th Mar 2019, 20:32
  #1993 (permalink)  
 
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Originally Posted by FCeng84 View Post
Need for MCAS is not related the thrust pitch coupling. Read previous thread entries to understand and catch up with the discussion.
I know the requirement for MCAS is to have linear alpha forces on the column as it approaches high AOA, as required by certification, due to the new lift generated by the engine nacelles not previously found in previous NG models.

I was trying to explain pitch-thrust coupling.
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Old 18th Mar 2019, 20:33
  #1994 (permalink)  
 
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Hi guys
A few points being missed here I think so far. Now some of these are of course just opinion but here goes.....
1 the 737 can fly with everything turned off. It’s a mechanical plane. That is it’s great virtue. So to crash one you have to forget that it’s actually a real ordinary plane and you are meant to be in total control! Always.
2 that being so, if STAB moves unexpectedly, turn off STAB SWITCHES as generations of pilots have done ,and fly straight and level. Why not take control of the plane? You can.
3 MACS only works with autopilot out at high AoA slow speed
4 the fact MACS malfunctions or maybe is not we’ll designed which we don’t know yet, is not the cause of the crash. although it would be desirable if it worked in a sensible manner. Eg two AoA inputs, doesn’t repeatedly incrementally trim nose down and a limit on the number of trim wheel turns etc etc as postulated here.
5 this nose down trim goes back to the 707 which had a stick pusher- it’s not really a new idea at all
6 the cause here? Looks to me like we’re forgetting the basics and the accumulated knowledge of 50 years of operating the 737.
as someone said, the MAX is like a cart (or perhaps a 707)with a couple of computers and glass screens, but underneath it’s a very simple uncomplicated plane. Fly it 6/60 and it will fly. 6 deg nose up. 60% power. Like any other plane.
7 the stabilizer trim switches on the yoke-the ones you use all the time, cannot apparently override (apply automatic brake) against MACS. Now- That’s something very different from the previous models and if true an important issue. But not the cause.
Thats my ten pence worth for today
i would fly a Max in a heartbeat. Provided the pilots
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Old 18th Mar 2019, 20:35
  #1995 (permalink)  
 
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Originally Posted by flyingchanges View Post
How many of you know what the stab trim range is in normal flight on your type. Might be a good time to pay attention to where your most powerful flight control spends most of its time. I know for our ops, the 800NG lives between 5 and 6 just about all of the time.

If the jet is doing something you don't want with a flight control, do something about it. I would call it a runaway, you can call it what you want. Yes, the trim moves a lot when hand flying, but it never moves enough to need substantial column input to counter it.
Music to my engineer ears! Let me add that the 737 automatic stabilizer control should never drive your airplane away from trim if you are flying at a steady speed and an AOA well below stick shaker. If it does, take note. Speaking of stick shaker, when that is going on a 737 MAX and the flaps are up and the autopilot is disengaged MCAS is most likely active. MCAS can activate with indicated AOA less than stick shaker, but it has to be close and must be above the AOA for any normal trim condition.
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Old 18th Mar 2019, 20:39
  #1996 (permalink)  
 
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Originally Posted by jagema View Post
I know the requirement for MCAS is to have linear alpha forces on the column as it approaches high AOA, as required by certification, due to the new lift generated by the engine nacelles not previously found in previous NG models.

I was trying to explain pitch-thrust coupling.
Great and peace. We just need to be careful in an MCAS focused discussion not to give the impression that the 737 MAX engine issue that gives rise to the need for MCAS is thrust pitch coupling. Glad that we are of the same understanding here.
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Old 18th Mar 2019, 20:40
  #1997 (permalink)  
 
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Originally Posted by FCeng84 View Post
Got it, thanks for expanding. What I was wanting to know if you were pointing to an explicit command limit within the control system that would keep from asking more of the elevator actuators than they can deliver vs. a system that asks for everything that is available and takes what it gets when elevator actuators are driven with full available hydraulic pressure. I am familiar with both types of systems. In the case of the 737 the limit is hydro-mechanical in that the elevator actuator control valves are wide open but the elevator hinge moment is more than the actuators can deliver so the surface ends up at a less than full travel position. I am familiar with this being referred to as either "blowdown" or "blowback". Note that if you are flying with high enough dynamic pressure for that to be the limiting factor and you command full elevator with full column and you hold that column and you speed up, the elevator deflection will decrease as dynamic pressure increases. With reference to Star Trek, that's when Scotty says "She's give'n you all there is, there just isn't any more to be had." Glad to provide this answer once I was certain of your question.

This question is for FCeng84 who seems to be very specifically knowledgeable regarding the 737Max. Based upon what you are saying about how the elevator works, it does not seem that there would be a situation that would, either through control force, aerodynamic force or a combination thereof, preclude manual trimming of the stabilizer. True?
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Old 18th Mar 2019, 20:43
  #1998 (permalink)  
 
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Smile

Originally Posted by FCeng84 View Post
Glad that we are of the same understanding here.
A lot of it has to do with your clear and insightful contributions to this thread. As a 737NG driver I thank you bud.
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Old 18th Mar 2019, 20:51
  #1999 (permalink)  
 
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Originally Posted by yanrair View Post
Hi guys
A few points being missed here I think so far. Now some of these are of course just opinion but here goes.....
1 the 737 can fly with everything turned off. It’s a mechanical plane. That is it’s great virtue. So to crash one you have to forget that it’s actually a real ordinary plane and you are meant to be in total control! Always.
2 that being so, if STAB moves unexpectedly, turn off STAB SWITCHES as generations of pilots have done ,and fly straight and level. Why not take control of the plane? You can.
3 MACS only works with autopilot out at high AoA slow speed
4 the fact MACS malfunctions or maybe is not we’ll designed which we don’t know yet, is not the cause of the crash. although it would be desirable if it worked in a sensible manner. Eg two AoA inputs, doesn’t repeatedly incrementally trim nose down and a limit on the number of trim wheel turns etc etc as postulated here.
5 this nose down trim goes back to the 707 which had a stick pusher- it’s not really a new idea at all
6 the cause here? Looks to me like we’re forgetting the basics and the accumulated knowledge of 50 years of operating the 737.
as someone said, the MAX is like a cart (or perhaps a 707)with a couple of computers and glass screens, but underneath it’s a very simple uncomplicated plane. Fly it 6/60 and it will fly. 6 deg nose up. 60% power. Like any other plane.
7 the stabilizer trim switches on the yoke-the ones you use all the time, cannot apparently override (apply automatic brake) against MACS. Now- That’s something very different from the previous models and if true an important issue. But not the cause.
Thats my ten pence worth for today
i would fly a Max in a heartbeat. Provided the pilots

A couple of responses to your points:

1. True, but you don't truly get everything turned off until you use the stabilizer cutout switches. Handling qualities are not certifiable in that configuration.

2. Fully agree.

3. MCAS can operate at any Mach number less than 0.84.

4. Fully agree. Hopefully the MCAS update to be fielded soon addresses all that you raise in this point.

5. There is a fundamental difference between a stick pusher and a system that uses stabilizer. The pitch command increment provided by a pusher is gone as soon as you override and move the column where you want it. The increment of stabilizer motion inserted automatically is not removed via the column and takes either returning to low AOA or pilot commanding the trim in the other direction. Running the stabilizer back takes time.

6. Pitch and power per book recommendations - yes!

7. Pilot operated pitch trim switches on the yoke will temporarily override MCAS. If the conditions for MCAS activation persist, it will come back active 5 seconds after the pilot stops trimming. Lion Air pilot demonstrated this for several minutes. The column cutout switches (not available to the pilot, but tripped when the column is far enough out of neutral) do override the legacy STS function, but do not override MCAS when pulling with MCAS commanding airplane nose down stabilizer.

Cheers

Last edited by FCeng84; 18th Mar 2019 at 21:05. Reason: typo
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Old 18th Mar 2019, 20:58
  #2000 (permalink)  
 
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Transport Canada Will Review

Canada re-examining Boeing 737 MAX approval after FAA certification probe

OTTAWA (Reuters) - Transport Canada is re-examining the validation it gave Boeing Co’s 737 MAX jets, following reports of a U.S. probe into the aircraft’s certification by the Federal Aviation Administration (FAA), Canadian Transport Minister Marc Garneau said on Monday.

Garneau told reporters in Ottawa that Transport Canada might not take any action but he thinks it would be wise to re-examine the validation of the 737 MAX 8 jet, which has been grounded worldwide for safety concerns following the recent crash of an Ethiopian plane of that model, which killed 157 people.

The disaster followed a Lion Air crash in Indonesia in October involving the same model plane.

Canada accepted the FAA’s March 2017 certification of the MAX under a deal where such approvals by the United States are accepted by Canada and vice versa.

“We may not change anything but we’ve decided it’s a good idea for us to review the validation of the type certificate that was given for the MAX 8,” he said.

Citing people familiar with the inquiry, the Wall Street Journal reported on Sunday that U.S. Department of Transportation officials were scrutinizing the FAA approval of MAX jets and that a grand jury in Washington subpoenaed at least one person involved in developing the MAX.

In addition, the Seattle Times reported that Boeing’s safety analysis of a new flight control system on MAX jets, known as MCAS, had several crucial flaws, including understating the power of the system.

Garneau said Transport Canada would do its own certification of a software change being prepared by Boeing within the next few weeks “even if it’s certified by the FAA.”

Reporting By David Ljunggren in Ottawa. Writing by Allison Lampert in Montreal; editing by Jonathan Oatis
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