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  #101  
Old 03-16-2019, 02:06 PM
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Originally Posted by Ale View Post
"It can't be fixed" is not acceptable, if the engine configuration leads to an airplane that makes it susceptible to losing control then they need to change that even if it means recalling all the airframes and rebuilding them.
You're looking at this on a very simplistic level. ALL airplanes have flight characteristics unique to their design. All of them. They must be flown according to these characteristics. A 747-8 is a much different airplane than a 747-100.

I'll give you a personal example. I changed to a more powerful engine in my plane. It was a custom design similar to another model of the same make. It added almost 40% more power. The differences between the two models is the cowling, a redistribution of parts under the cowling, and lack of flaps. The balance of the plane was close to identical between them. The end result were flight characteristics unique to the plane. If you flew it like the original or the similar hp model you were in for a surprise.

Every single plane model is different. The goal is to make them fly as similar as possible to designs in the same general category. Boeing did this with the 757 and 767. One is a narrow body and the other a wide body yet the type certification is the same. The 737 series is no different in this respect. The goal is to make it fly as close to as many other aircraft as possible.

Commercial airlines are fly-by-wire. Virtually all control inputs are made using artificial feedback. The plane is doing what the computer interprets the pilot wants to do. The pilot is engaging the controls based on how they feel. The initial public speculation on the 737-max problem is that a negative feedback loop exists with the MCAS system. Boeing's solution seems to indicate this is the problem. They are limiting the number of computer generated corrections in this system to one cycle.

It might have been solved with training but 2 major crashes demand something of a more tangible nature.
  #102  
Old 03-16-2019, 02:19 PM
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Originally Posted by GreenWyvern View Post
The best summary I've seen of the situation comes from an anonymous engineer commenting in the New York Times:
That is yellow journalism at it's worst. No engineer with an atom's worth of integrity would have written that.

the best aircraft in the world are often based on robust platforms which evolved through generations of improvements.

The reason the engineer is anonymous is that he or she would have their ass reamed professionally for such commentary.

A complete clown-fuck piece of non-journalism that deserves an apology from the paper and public exposure of the "engineer".
  #103  
Old 03-16-2019, 03:21 PM
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Originally Posted by scr4 View Post
Could they have fixed the issue with a larger horizontal stabilizer, or is there more to it?
I don't think the issue is elevator authority. It's not a function of not being able to alter angle of attack. The nose of any airplane will rise and fall under various inputs. It's a function of reacting to the change in pitch.

In this case the pilot is allowing the nose to come up higher than it should and the plane independently making adjustments.

If I understand this correctly it's not happening with the auto climb engaged but rather when it's manually flown.
  #104  
Old 03-16-2019, 06:19 PM
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I don't think the issue is elevator authority. It's not a function of not being able to alter angle of attack. The nose of any airplane will rise and fall under various inputs. It's a function of reacting to the change in pitch.
I was trying to understand if it's not just a matter of center of aerodynamic pressure being too far forward. I suppose not.
  #105  
Old 03-16-2019, 06:51 PM
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If there are people who track such stats, does it seem that Boeing jets crash far more often, on a per-jet basis, than Airbuses?


(Some of those aren't Boeing's fault, of course, but were caused by malicious human action instead - all four airliners hijacked on 9/11 were Boeings, the Malaysian 370 possible-pilot-suicide was a Boeing, the Egyptair pilot suicide was a Boeing, the SilkAir pilot suicide was a Boeing, the Malaysian jet shot down by Russian missiles was a Boeing, the Pan Am Lockerbie bombing was a Boeing, the Korean Air Soviet shootdown was a Boeing, the Ethiopian hijacked crashing in the sea in the 1990s was a Boeing, etc.)

Last edited by Velocity; 03-16-2019 at 06:53 PM.
  #106  
Old 03-16-2019, 07:21 PM
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Originally Posted by Velocity View Post
(Some of those aren't Boeing's fault, of course, but were caused by malicious human action instead - all four airliners hijacked on 9/11 were Boeings, the Malaysian 370 possible-pilot-suicide was a Boeing, the Egyptair pilot suicide was a Boeing, the SilkAir pilot suicide was a Boeing, the Malaysian jet shot down by Russian missiles was a Boeing, the Pan Am Lockerbie bombing was a Boeing, the Korean Air Soviet shootdown was a Boeing, the Ethiopian hijacked crashing in the sea in the 1990s was a Boeing, etc.)
Great cherrypicking of data. Now give us a list of the non-Boeing crashes, bombings, and accidents, like Air France 447, so we can compare. Got any more?
  #107  
Old 03-16-2019, 09:20 PM
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Great cherrypicking of data. Now give us a list of the non-Boeing crashes, bombings, and accidents, like Air France 447, so we can compare. Got any more?
I think you missed my point.
  #108  
Old 03-16-2019, 10:58 PM
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Page 18 has a graph with accident rates by airplane type, 1959 through 2017:

https://www.boeing.com/resources/boe...df/statsum.pdf
  #109  
Old Yesterday, 12:24 AM
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Originally Posted by Magiver View Post
That is yellow journalism at it's worst. No engineer with an atom's worth of integrity would have written that.

the best aircraft in the world are often based on robust platforms which evolved through generations of improvements.
Except it appears to be true. I think you have a naive or idealized view of the way big corporations make decisions.

Look on any forum for professional pilots, like pprune.org (thread on the Ethiopian airliner crash currently 87 pages long) or aviation24.be and see what they they are saying about MCAS.
  #110  
Old Yesterday, 12:31 AM
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Originally Posted by Magiver View Post
You're looking at this on a very simplistic level. ALL airplanes have flight characteristics unique to their design. All of them. They must be flown according to these characteristics. A 747-8 is a much different airplane than a 747-100.

I'll give you a personal example. I changed to a more powerful engine in my plane. It was a custom design similar to another model of the same make. It added almost 40% more power. The differences between the two models is the cowling, a redistribution of parts under the cowling, and lack of flaps. The balance of the plane was close to identical between them. The end result were flight characteristics unique to the plane. If you flew it like the original or the similar hp model you were in for a surprise.

Every single plane model is different. The goal is to make them fly as similar as possible to designs in the same general category. Boeing did this with the 757 and 767. One is a narrow body and the other a wide body yet the type certification is the same. The 737 series is no different in this respect. The goal is to make it fly as close to as many other aircraft as possible.

Commercial airlines are fly-by-wire. Virtually all control inputs are made using artificial feedback. The plane is doing what the computer interprets the pilot wants to do. The pilot is engaging the controls based on how they feel. The initial public speculation on the 737-max problem is that a negative feedback loop exists with the MCAS system. Boeing's solution seems to indicate this is the problem. They are limiting the number of computer generated corrections in this system to one cycle.

It might have been solved with training but 2 major crashes demand something of a more tangible nature.
I design and build model airplanes and drones for a hobby, I know how much of an exercise in compromising attributes it is to design airplanes.
Also know full well what a complete pig to fly a design with poor stability is, be it from static or dynamic stability reasons. For example, would you be comfortable flying in your airplane if you knew the only thing that keeps it from going into a divergent fugoid is an electronic flight controller, IOW one more thing that can fail?

The issue, ISTM, is precisely that the 737 MAX does not fly as the previous models, if it did it wouldn't need this new artificial stability system, would it?

The design compromise Boeing made when they decided they'd go ahead an inherently unstable airplane for the sake of saving on design and manufacturing costs and trying to fix it via software, has already cost the lives of almost 350 people in just six months.

So what would the solution be? As Richard Pearce pointed out the plane could not be certified unless it had the artificial stability system, that means, I presume, that as-is the plane has unsafe flight characteristics. Yes they could change the MCAS for something that doesn't kill everyone on board when it glitches but that is still another layer of complexity to paper over the fact that the design has, presumably, unsafe flight characteristics.
That is why I think the solution would be to fix the airframe, and if that is not economically feasible too bad for Boeing but enough people have already died because they stuffed up royally.
  #111  
Old Yesterday, 01:53 AM
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Originally Posted by Ale View Post
I design and build model airplanes and drones for a hobby, I know how much of an exercise in compromising attributes it is to design airplanes.
Well I've built, modified and certified a real airplane and have flown it. so, your example of models is noted for discussion. Not to be rude but models don't mean much beyond wind tunnel data.

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Originally Posted by Ale View Post
Also know full well what a complete pig to fly a design with poor stability is, be it from static or dynamic stability reasons. For example, would you be comfortable flying in your airplane if you knew the only thing that keeps it from going into a divergent fugoid is an electronic flight controller, IOW one more thing that can fail?
Every single airplane built today is fly by wire and the "stability" of the plane is software linked to engineered tactile input to the pilot.

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Originally Posted by Ale View Post
IThe issue, ISTM, is precisely that the 737 MAX does not fly as the previous models, if it did it wouldn't need this new artificial stability system, would it?
none of the previous models fly the same as the previous models. each model is a stand-alone engineering design.

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Originally Posted by Ale View Post
The design compromise Boeing made when they decided they'd go ahead an inherently unstable airplane for the sake of saving on design and manufacturing costs and trying to fix it via software, has already cost the lives of almost 350 people in just six months.
there is no "compromise" between models per se. The next generation of each aircraft is effectively a new aircraft based on previous construction techniques.

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So what would the solution be?
The solution is a system that reacts to anticipated pilot inputs. If there is a flaw in that system it needs to be fixed. If there is a flaw in flying parameters then that has to be fixed.
  #112  
Old Yesterday, 02:46 AM
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It looks like the problem with the software is not easy to fix, and may have run into unanticipated difficulties. After the previous crash, Boeing promised an update by the end of 2018. Now we are still waiting for the update, even though it's costing Boeing a fortune. On Friday they were still saying, "no later than April".
  #113  
Old Yesterday, 04:36 AM
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An article in The Air Current has some interesting insights into the financial pressures on Boeing, after the American Airlines decision in 2011 to buy 260 Airbus aircraft.

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Boeing wanted to replace the 737. The plan had even earned the endorsement of its now-retired chief executive. “We’re gonna do a new airplane,” Jim McNerney said in February of that same year. “We’re not done evaluating this whole situation yet, but our current bias is to not re-engine, is to move to an all-new airplane at the end of the decade.” History went in a different direction. Airbus, riding its same decades-long incremental strategy and chipping away at Boeing’s market supremacy, had made no secret of its plans to put new engines on the A320. But its own re-engined jet somehow managed to take Boeing by surprise. Airbus and American forced Boeing’s hand. It had to put new engines on the 737 to stay even with its rival.

Boeing justified the decision thusly: There were huge and excruciatingly painful near-term obstacles on its way to a new single-aisle airplane. In the summer of 2011, the 787 Dreamliner wasn’t yet done after billions invested and years of delays. More than 800 airplanes later here in 2019, each 787 costs less to build than sell, but it’s still running a $23 billion production cost deficit. A new single-aisle jet risked unlocking all its stalwart operators who banked on the continuity between 737 generations.

An all-new jet meant leaving the past behind, along with its established infrastructure. With a lower-cost alternative in the A320neo not hamstrung by having to pay for a fresh $15 billion development, a new Boeing jet risked giving Airbus dominant market share. In the wake of a record oil run-up in 2008, airlines wanted fuel efficiency at a current-technology price.

The 737 Max was Boeing’s ticket to holding the line on its position – both market and financial – in the near term. Abandoning the 737 would’ve meant walking away from its golden goose that helped finance the astronomical costs of the 787 and the development of the 777X.

The 737 Max is a product of that environment where short-term decision-making can drive big and often painful pushes for product improvement. It’s one that I’ve written about extensively over the years, and born from the work of academics like Dr. Theodore Piepenbrock and his work on the Evolution of Business Ecosystems.

Every airplane development is a series of compromises, but to deliver the 737 Max with its promised fuel efficiency, Boeing had to fit 12 gallons into a 10 gallon jug. Its bigger engines made for creative solutions as it found a way to mount the larger CFM International turbines under the notoriously low-slung jetliner. It lengthened the nose landing gear by eight inches, cleaned up the aerodynamics of the tail cone, added new winglets, fly-by-wire spoilers and big displays for the next generation of pilots. It pushed technology, as it had done time and time again with ever-increasing costs, to deliver a product that made its jets more-efficient and less-costly to fly.

In the case of the 737 Max, with its nose pointed high in the air, the larger engines – generating their own lift – nudged it even higher. The risk Boeing found through analysis and later flight testing was that under certain high-speed conditions both in wind-up turns and wings-level flight, that upward nudge created a greater risk of stalling. Its solution was MCAS, the Maneuvering Characteristics Augmentation System control law that would allow for both generations of 737 to behave the same way. MCAS would automatically trim the horizontal stabilizer to bring the nose down, activated with Angle of Attack data. It’s now at the center of the Lion Air investigation and stalking the periphery of the Ethiopian crash.

There is also an interesting light on the Lion Air crash:

Quote:
Lion Air 610 should never have been allowed to get airborne on October 29, a conclusion shared by those familiar with the inquiry. The plane simply wasn’t airworthy. According to the preliminary investigation, PK-LQP’s Angle of Attack sensors were disagreeing by 20-degrees as the aircraft taxied for takeoff. A warning light that would’ve alerted the crew to the disagreement wasn’t part of the added-cost optional package of equipment on Lion Air’s 737 Max aircraft. A guardrail wasn’t in place. Once the aircraft was airborne, the erroneous Angle of Attack data collided with an apparently unprepared crew with tragic consequences as the MCAS system repeatedly activated, driving the jet’s nose into a fatal dive.
Boeing has refused to comment on making the AOA disagreement alert optional, at extra cost. Since there were only two AOA sensors, the MCAS system couldn't determine the correct AOA once one sensor failed.

And the pilots hadn't been trained on the MCAS because Boeing hadn't deemed it necessary...
  #114  
Old Yesterday, 05:20 AM
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Originally Posted by Magiver View Post
Every single airplane built today is fly by wire and the "stability" of the plane is software linked to engineered tactile input to the pilot.

...

none of the previous models fly the same as the previous models. each model is a stand-alone engineering design.
Your first comment isn’t true. It’s nearly true and I wouldn’t have bothered to correct it except that the aircraft under discussion is not fly-by-wire itself. All the other main players are, the A320 and all subsequent Airbus models are FBW, the B777 and B787 are FBW, but the B737, being a really fricken old design, is not, not even the MAX.

The second isn’t really true either. Typically in the past, making a new version of an existing design has involved extending the fuselage by literally adding fuselage plugs forward and aft of the wing, and upgrading the engines. The end result feels much the same to fly, it might be heavier but have the same wing which means the speeds are a bit faster and perhaps it will feel a touch heavier on the controls. Any real differences tend to be at the edge of the envelope where no one intentionally flies anyway.

I’m not quite sure where I stand on the wisdom of using a software solution to an aerodynamic problem. On first glance I would agree that it is not reasonable to allow an uncertifiable airframe to be fixed with a “patch”, for want of a better word. But on the other hand that is exactly what stick shakers and stick pushers are, without these no airliner would be certifiable but we’ve been accepting of those for several generations of jet transport aircraft.

I think where MCAS falls down is that it only needs one AOA sensor to activate it. Where stick pushers are fitted they typically need both AOA vanes to sense an impending stall. Pushers can also be physically over powered, they can be shut off by dedicated shut off buttons that light up when the pusher activates, and they are a system unlike any other so they can’t be confused with anything else. My understanding is that MCAS solves a slightly different problem to a pusher, but a misbehaving MCAS is just as dangerous as a spurious stick push and so should probably incorporate similar design philosophies.

By the way, something I learned researching for this thread, Boeing’s in general don’t have stick pushers. My previous experience has been with T-tail turboprops and jets and they have mostly had stick pushers due to their ability to “deep stall”, the turbulent air off the stalled wing blankets the tail plane robbing it of the necessary control authority to pitch down and recover from the stall. This experience lead me to believe that pushers were more common than they actually are.

Last edited by Richard Pearse; Yesterday at 05:21 AM.
  #115  
Old Yesterday, 10:59 AM
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Originally Posted by Richard Pearse View Post
Your first comment isn’t true. It’s nearly true and I wouldn’t have bothered to correct it except that the aircraft under discussion is not fly-by-wire itself. All the other main players are, the A320 and all subsequent Airbus models are FBW, the B777 and B787 are FBW, but the B737, being a really fricken old design, is not, not even the MAX.
Fly-by-wire was a poor choice of words. All modern aircraft use augmented drive systems where the input of the pilot is translated to a system of electro/hydraulic mechanisms. The feedback to the pilot is artificially driven by design. If you look at the A/A flt 587 crash it was the result of artificially light pedal feel and their there was a change in pedal feedback plus inadequate rudder limits. If I'm remembering it correctly these were changes made to the design of the plane from one model to the next.

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Originally Posted by Richard Pearse View Post
The second isn’t really true either. Typically in the past, making a new version of an existing design has involved extending the fuselage by literally adding fuselage plugs forward and aft of the wing, and upgrading the engines. The end result feels much the same to fly, it might be heavier but have the same wing which means the speeds are a bit faster and perhaps it will feel a touch heavier on the controls. Any real differences tend to be at the edge of the envelope where no one intentionally flies anyway
Well yes and no. If you look at a DC8 the segmentation is as you describe and probably had similar feel until they got to the CFM engines. The DC-9 conversion to the MD-80 looks like it was segmented forward of the wings. But conversion may be the wrong word to use. Maybe design extension is a better word. I suspect the MD-80 has a different feel to it than a DC-9 but I've never asked a pilot who has flown both.


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Originally Posted by Richard Pearse View Post
I’m not quite sure where I stand on the wisdom of using a software solution to an aerodynamic problem. On first glance I would agree that it is not reasonable to allow an uncertifiable airframe to be fixed with a “patch”, for want of a better word. But on the other hand that is exactly what stick shakers and stick pushers are, without these no airliner would be certifiable but we’ve been accepting of those for several generations of jet transport aircraft.
Computers have blurred the interface between pilot and plane. When planes got so big that pilots could not physically operate a cabled control surface then control feedback became an artificial creation. Computers can be reconfigured easier for feedback. And as automated trim systems are added a computer is easier to reconfigure.

The word "patch" is as you suggest, a tricky word to use. All airplane designs have unique characteristics. Certification, IMO, is a process of identifying structural limitations and ensuring the plane does not operate beyond those limits. I've never liked the idea of a computer overriding a pilot's input in a way that is invisible to the pilot. To me that's a patch. But that's what roll control does.

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Originally Posted by Richard Pearse View Post
I think where MCAS falls down is that it only needs one AOA sensor to activate it. Where stick pushers are fitted they typically need both AOA vanes to sense an impending stall. Pushers can also be physically over powered, they can be shut off by dedicated shut off buttons that light up when the pusher activates, and they are a system unlike any other so they can’t be confused with anything else. My understanding is that MCAS solves a slightly different problem to a pusher, but a misbehaving MCAS is just as dangerous as a spurious stick push and so should probably incorporate similar design philosophies.
If it were me, I'd like a visual indication that the MCAS is overriding pilot or autopilot commands and I'd want the disconnect to the MCAS located next to this visual display.

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Originally Posted by Richard Pearse View Post
By the way, something I learned researching for this thread, Boeing’s in general don’t have stick pushers. My previous experience has been with T-tail turboprops and jets and they have mostly had stick pushers due to their ability to “deep stall”, the turbulent air off the stalled wing blankets the tail plane robbing it of the necessary control authority to pitch down and recover from the stall. This experience lead me to believe that pushers were more common than they actually are.
Interesting.
  #116  
Old Yesterday, 11:01 AM
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Boeing has refused to comment on making the AOA disagreement alert optional, at extra cost. Since there were only two AOA sensors, the MCAS system couldn't determine the correct AOA once one sensor failed.

And the pilots hadn't been trained on the MCAS because Boeing hadn't deemed it necessary...
I imagine the crash summary is going to read like this.
  #117  
Old Yesterday, 04:22 PM
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If it were me, I'd like a visual indication that the MCAS is overriding pilot or autopilot commands and I'd want the disconnect to the MCAS located next to this visual display.

Interesting.
I am not a pilot and understand only the most basic basics of aviation and piloting.

I was thinking about 2001: A Space Odyssey (bear with me a moment... ) where you often see a video monitor in the background with a random combination of 3 capital letters. I always wondered what those were supposed to indicate. No one seems to ever look at them but maybe they would be critical information in some situation.

That led to me imagine a small monitor in the cockpit that lists what changes the auto-pilot or other systems are making to the pilots inputs at any given time with significant changes high-lighted. It'd be something the pilots never even look at unless they were trying to troubleshoot really bizarre aircraft behavior where they could see at a glance what auto-system is being activated and when.

Seems like that could clear up a lot of confusion during a crisis.
  #118  
Old Yesterday, 07:23 PM
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I did mean AGL. During take off and subsequent climb the aircraft will become airborne at whatever the calculated indicated air speed was, let’s say 140 knots (it depends on many factors including weight and flap setting), it will then climb at a slightly higher speed, eg 150 knots, to the acceleration altitude. The acceleration altitude is the altitude at which it’s calculated it is safe to accelerate to a faster speed, normally 250 knots, and retract the flaps. Although it is expressed as an altitude AMSL, it is actually defined by height above the ground. Additionally, an airline will have a minimum acceleration altitude. The acceleration altitude may be higher than the minimum in order to out climb a building or hill, but it can’t be lower. Where I work our min acceleration altitude is 1500’ above the ground. 250 knots is then flown until any air traffic control speed restrictions cease to apply.

The initial climb profile then is all based on height above ground and you can’t compare speeds of aircraft if one of them is relatively low AGL because it won’t have accelerated to its final climb speed yet.

Whether or not 383 knots is above the Vmo for the B737, it is certainly going very fast, a good 200 knots faster than would be typical for the initial climb.
Perhaps I'm missing your point here, but relating altitude AGL to the phase of a flight is only valid for normal flight profiles, which Ethiopian most certainly was not. Your statement about low airspeed during the initial climb is certainly true and borne out by my cited reference flight of a MAX 8 in a normal climb, which was only doing about 200 kts (ground speed) as it approached 1500 AGL, pretty much as you describe. But it was doing this less than 60 seconds after takeoff -- by the time it had been in the air three minutes (where contact with Ethiopian was lost) it had already climbed to an altitude of over 7500 ft AGL.

I would guess (strictly a WAG) that Ethiopian's relatively high speed was some combination of unintended powered descents and likely the pilot throttling up as he fought a possible nose-down trim problem.

The latest announcement from the Ethiopian transport minister was that the flight data recorder is already yielding evidence of "clearly similar" behavior to Lion Air -- but no further details were provided.
  #119  
Old Yesterday, 07:40 PM
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Originally Posted by I Love Me, Vol. I View Post
I am not a pilot and understand only the most basic basics of aviation and piloting.

I was thinking about 2001: A Space Odyssey (bear with me a moment... ) where you often see a video monitor in the background with a random combination of 3 capital letters. I always wondered what those were supposed to indicate. No one seems to ever look at them but maybe they would be critical information in some situation.

That led to me imagine a small monitor in the cockpit that lists what changes the auto-pilot or other systems are making to the pilots inputs at any given time with significant changes high-lighted. It'd be something the pilots never even look at unless they were trying to troubleshoot really bizarre aircraft behavior where they could see at a glance what auto-system is being activated and when.
That is a standard feature of modern aircraft. It is called the Flight Mode Annunciator (FMA) and lives at the top of the primary flight display (PFD). Rather than being something that is hardly ever looked at, the pilots live by it. In the Airbus world "understand your FMA at all times" is rule number 3 of their golden rules. The FMA is a window into the soul of the aircraft, it tells you what it is doing. Any changes to the FMA, ie a new mode becomes active, are boxed in white for a few seconds and must be called out by the pilot flying so that both pilots are aware of the current mode status of the aircraft. Any downgrade in FMA, ie a change from a high level of automation to a lower level, will be accompanied by a triple click sound.

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Seems like that could clear up a lot of confusion during a crisis.
It can go a long way toward preventing a crisis in the first place. Unfortunately, once the crisis hits the poor human brain tends to get a bit of information overload. An argument for not having humans at all? Not really, the crisis normally happens when the automatic systems have already failed to do their job.



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Originally Posted by Magiver View Post
Fly-by-wire was a poor choice of words. All modern aircraft use augmented drive systems where the input of the pilot is translated to a system of electro/hydraulic mechanisms. The feedback to the pilot is artificially driven by design. If you look at the A/A flt 587 crash it was the result of artificially light pedal feel and their there was a change in pedal feedback plus inadequate rudder limits. If I'm remembering it correctly these were changes made to the design of the plane from one model to the next.
Yes, the feel is artificial, not necessarily electronic computers by the way, mechanical systems of springs and weights do a perfectly good job
Quote:
If you look at a DC8 the segmentation is as you describe and probably had similar feel until they got to the CFM engines. The DC-9 conversion to the MD-80 looks like it was segmented forward of the wings. But conversion may be the wrong word to use. Maybe design extension is a better word. I suspect the MD-80 has a different feel to it than a DC-9 but I've never asked a pilot who has flown both.
I've flown short and long versions of the Dash 8 and short / long versions of the BAe146. If I wasn't told which I was flying, I wouldn't know the difference. They don't have any computers either, the ailerons and elevators are operated by cables and pulleys.


Quote:
Computers have blurred the interface between pilot and plane. When planes got so big that pilots could not physically operate a cabled control surface then control feedback became an artificial creation. Computers can be reconfigured easier for feedback. And as automated trim systems are added a computer is easier to reconfigure.
There's a difference between adding feedback to a system because it is controlled remotely and the controller wouldn't otherwise feel any feedback, and adding feedback to mask unsavoury handling characteristics.

Quote:
The word "patch" is as you suggest, a tricky word to use. All airplane designs have unique characteristics. Certification, IMO, is a process of identifying structural limitations and ensuring the plane does not operate beyond those limits. I've never liked the idea of a computer overriding a pilot's input in a way that is invisible to the pilot. To me that's a patch. But that's what roll control does.
It all depends on why the computers, if there are any, are doing what they are doing. In the Airbus A320 and A321 the normal control law does all sorts of shit in order to make it really easy and safe to fly. It trims automatically and it waggles the ailerons, spoilers, and elevators around so that when you set an attitude it stays there. When you get below 50' during a landing it trims nose down so that you have to hold back pressure on the stick during the flare just like you do in any other plane.

The thing is though, you can turn two of three redundant systems off, the inertial reference systems, and it reverts to direct law. Direct law is exactly like a Cessna 172, there's no auto trim at all and the flight controls are moved in direct proportion to the control input. It flies perfectly well like this, there are no vices, and it doesn't do anything odd, this is because the fundamental aerodynamics are sound. It is not an unstable FBW fighter jet that would not be flyable without the FBW, it's a conventionally stable aircraft that has FBW to make the pilot's job a little easier.

It seems to me like the re-engined 737 may have lost the fundamentals at some point in the design process. That said, the MCAS is a system that operates near the edge of the envelope, it's not like it is intruding all the time. I'd suspect that in normal ops a pilot would never see it operate.

Quote:
If it were me, I'd like a visual indication that the MCAS is overriding pilot or autopilot commands and I'd want the disconnect to the MCAS located next to this visual display.
Yeah. Or make it like the stick pusher systems I've seen where the visual display and the deactivate button are the same thing (buttons light up, push the buttons to deactivate). More importantly, make the MCAS require two high AOA inputs, not just one.
  #120  
Old Yesterday, 07:46 PM
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Perhaps I'm missing your point here, but relating altitude AGL to the phase of a flight is only valid for normal flight profiles, which Ethiopian most certainly was not. Your statement about low airspeed during the initial climb is certainly true and borne out by my cited reference flight of a MAX 8 in a normal climb, which was only doing about 200 kts (ground speed) as it approached 1500 AGL, pretty much as you describe. But it was doing this less than 60 seconds after takeoff -- by the time it had been in the air three minutes (where contact with Ethiopian was lost) it had already climbed to an altitude of over 7500 ft AGL.

I would guess (strictly a WAG) that Ethiopian's relatively high speed was some combination of unintended powered descents and likely the pilot throttling up as he fought a possible nose-down trim problem.

The latest announcement from the Ethiopian transport minister was that the flight data recorder is already yielding evidence of "clearly similar" behavior to Lion Air -- but no further details were provided.
Yeah, perhaps we are talking past each other. You were comparing the Ethiopian speed to some other flight profiles at similar altitude AMSL which showed the Ethiopian aircraft was going a bit faster, but not massively so. All I meant was that, when compared to the profile it should have been flying reference the ground, it was going nearly twice as fast, which shows it was way out of control in terms of speed.
  #121  
Old Yesterday, 07:54 PM
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Word from Air Canada shortly after the announcements of the grounding was that they expected it to last at least three weeks. With the apparently growing evidence of similarities between the two MAX 8 accidents it may be longer, perhaps with improvements like some of the ones being discussed here being added, in addition to software changes already planned. I bet one of the most valuable airplanes right now on the lease market is any 737 that isn't a MAX, that could be directly substituted into the gaping holes in airlines' schedules.
  #122  
Old Yesterday, 08:09 PM
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If nothing else, this should give more impetus to Boeing's upcoming 797 - which IIRC is supposed to replace the 737, 757 and 767 all in one.
  #123  
Old Yesterday, 08:16 PM
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I don't think so. 350 MAX 8s have been delivered so far, and there are firm orders for over 4,600 more 737 MAX models of all variants. This is a problem that has to be fixed, and fixed well, once and for all, not written off.
  #124  
Old Yesterday, 09:44 PM
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Yeah. Or make it like the stick pusher systems I've seen where the visual display and the deactivate button are the same thing (buttons light up, push the buttons to deactivate). More importantly, make the MCAS require two high AOA inputs, not just one.
I like that.
  #125  
Old Yesterday, 11:52 PM
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I didn't read the Seattle Times article due to paywall, but others are quoting it as saying Boeing admits there was a flaw in their safety analysis (which the FAA assigned to Boeing due to budget cuts).

This article references the Seattle Times article.
https://moneymaven.io/mishtalk/econo...kuZLkDJn3Jy8A/

"The safety analysis:

1 - Understated the power of the new flight control system, which was designed to swivel the horizontal tail to push the nose of the plane down to avert a stall. When the planes later entered service, MCAS was capable of moving the tail more than four times farther than was stated in the initial safety analysis document.

2 - Failed to account for how the system could reset itself each time a pilot responded, thereby missing the potential impact of the system repeatedly pushing the airplane’s nose downward.

3 - Assessed a failure of the system as one level below “catastrophic.” But even that “hazardous” danger level should have precluded activation of the system based on input from a single sensor — and yet that’s how it was designed."
  #126  
Old Today, 02:36 AM
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The Seattle Times article is the best comprehensive analysis I've seen so far.

Beyond all the technical details covered, it pinpoints the ultimate cause of the crash - that the FAA delegated oversight to Boeing itself. It was a failure of regulation and oversight, due to FAA management being in bed with Boeing.
  #127  
Old Today, 02:45 AM
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Have to wonder if the "Hands off business - less regulation" theme in government the last few Republican administrations might have been part of that.
  #128  
Old Today, 05:01 AM
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The Seattle Times article is the best comprehensive analysis I've seen so far.



Beyond all the technical details covered, it pinpoints the ultimate cause of the crash - that the FAA delegated oversight to Boeing itself. It was a failure of regulation and oversight, due to FAA management being in bed with Boeing.
We don't know the cause of the crashes yet, we need to wait for the investigations to finish.

While the Seattle Times article is quite comprehensive and has lots of detail, there is a lot of speculation and inaccuracies, so need to wait for factual reports.

NB
  #129  
Old Today, 06:37 AM
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We don't know the cause of the crashes yet, we need to wait for the investigations to finish.

While the Seattle Times article is quite comprehensive and has lots of detail, there is a lot of speculation and inaccuracies, so need to wait for factual reports.
True, of course. The black box information hasn't even become available yet.

But that report, and others from reputable media, are based on interviews with engineers inside Boeing and the FAA. And it seems like a consensus is emerging about what the problems were, and what likely happened.
  #130  
Old Today, 10:56 AM
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Have to wonder if the "Hands off business - less regulation" theme in government the last few Republican administrations might have been part of that.
Let's check the facts:
1 - 737 MAX project launched 2011 with FAA certification in 2017
2 - Obama's admin: 2009 through 2017


Yep, it's definitely the Republicans.

Last edited by RaftPeople; Today at 10:56 AM.
  #131  
Old Today, 11:49 AM
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Have to wonder if the "Hands off business - less regulation" theme in government the last few Republican administrations might have been part of that.
Quote:
Originally Posted by RaftPeople View Post
Let's check the facts:
1 - 737 MAX project launched 2011 with FAA certification in 2017
2 - Obama's admin: 2009 through 2017


Yep, it's definitely the Republicans.
The crucial question is when did the FAA change their policy and start delegating certification to the manufacturer. And was that change a result of Administration guidance.
  #132  
Old Today, 11:51 AM
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Let's check the facts:
1 - 737 MAX project launched 2011 with FAA certification in 2017
2 - Obama's admin: 2009 through 2017


Yep, it's definitely the Republicans.
2011-2018 Republican controlled House
2015-present Republican controlled Senate

Which party wants less government regulations, less oversight, less intrusion into business?
  #133  
Old Today, 12:15 PM
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2 - Obama's admin: 2009 through 2017
Uh...according to Wikipedia:

Quote:
The presidency of Donald Trump began at noon EST on January 20, 2017, when Donald Trump was inaugurated as the 45th president of the United States, succeeding Barack Obama.
You're rounding 19-and-a-half days up to 365?
  #134  
Old Today, 02:10 PM
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Regarding congress: valid point, repubs in congress can influence FAA funding.


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Uh...according to Wikipedia:

You're rounding 19-and-a-half days up to 365?
FAA funding was passed in 2012 for a 5 year period and then again in July of 2016 which ran through Sept 2017.

The Obama+congress deal could have been influenced by repubs, but I don't think they asked Trump for his opinion.
  #135  
Old Today, 02:36 PM
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At least one Congressional subpoena has apparently been issued, regarding the FAA's certification of the 737 Max. As per CBS News:

Quote:
Congress plans to probe the FAA approval process for the new Boeing 737 Max, and CBS News has learned that at least one Boeing employee and an FAA staffer involved with the certification of the Max planes have been told to retain records pertaining to that approval process.

Government officials with knowledge of the situation did not dispute on Monday that a Boeing official had received a subpoena to preserve records relating to the FAA certification process of the 737 Max.
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