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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. |
Originally Posted by vlieger
(Post 10422892)
https://www.marxist.com/737-max-scan...ore-safety.htmA 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. |
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. 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. 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. 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:
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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. |
Originally Posted by dozing4dollars
(Post 10422907)
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. |
Originally Posted by FCeng84
(Post 10422905)
Need for MCAS is not related the thrust pitch coupling. Read previous thread entries to understand and catch up with the discussion.
I was trying to explain pitch-thrust coupling. |
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 |
Originally Posted by flyingchanges
(Post 10422917)
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. |
Originally Posted by jagema
(Post 10422928)
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. |
Originally Posted by FCeng84
(Post 10422925)
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? |
Originally Posted by FCeng84
(Post 10422938)
Glad that we are of the same understanding here.
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Originally Posted by yanrair
(Post 10422930)
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 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 |
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 |
The most desirable outcome would be where manufacturers could design new aircraft with state of the art materials, engines and avionics instead of using airframes and certifications from the sixties. The cost of entry is so high this inhibites innovation and safety. Recently a Canadian design that competed with Boeing was blocked by Boeing because it was a competitor. Airbus stepped in to scoop up the newly certified C series and rebrand it an Airbus A220. Not what Boeing wanted. If the cost of certification is so high and established manufacturers block new entrants the safety and innovation that has been a hallmark of aviation will suffer. Flying sixties designs with bandaid fixes will be our future and our grandchildrens |
Originally Posted by abdunbar
(Post 10422939)
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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Well, if questions are permitted from professional engineers, here are two dumb questions:-
1. Looking at the altitude plot in post 1869, the clearance from rising terrain at 02.40 is perilously small, but thereafter there is a brisk climb. Could that rate of climb and altitude gain have taken the aircraft into a stall? 2. Eyewitnesses claimed to have seen items falling from the plane whilst it was still airborne. Could these have been contrails/vortices generated by extreme AoAs? Thank you in anticipation of patient and polite replies. |
Originally Posted by silverstrata
(Post 10422776)
Clearly MCAS is not a runnaway trim condition, otherwise we would be reaching for the cut-out switches every time the speed-trim operated. I think some people here do not realise that the trimmer doing its own thing is operations normal. And the auro-trim systems are always mis-trimming the aircraft (the trim inputs by the speed-trim system are always wrong, and you always have to re-trim manually). So at what point does ‘operations normal’ become ‘operations abnormal’? At what point do you assume that the trimmer has gone awry..?? Silver |
Originally Posted by FCeng84
(Post 10422925)
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.
My point.... and I do have one.... is that the elevator may have increasingly limited authority as the aircraft AS increased. |
Originally Posted by dozing4dollars
(Post 10422831)
The USA government shutdown that both political parties participated in was also a factor. ... and hence, the voters like you |
Originally Posted by dozing4dollars
(Post 10422993)
The Q limiter was pure mechanical and it limited rudder (DC-9). Same vintage as original B737. I don’t know what the MAX or NG has but I believe all modern jet transport aircraft limit fight controls as Q increases as well as Mach. My point.... and I do have one.... is that the elevator may have increasingly limited authority as the aircraft AS increased. On 737 the maximum elevator displacement with full column input is either full travel if the elevator actuators are physically capable of pushing the elevators hard enough to get there or where ever the aerodynamic hinge moment balances out against full elevator actuator force capability. In both cases, the control system is trying to move the elevator as far as is physically possible but in high dynamic pressure case it has reached an actuator force limit. On 787 the maximum elevator displacement with full column input is limited by a control system command limit schedule that is a function of flight condition. (I am simplifying here by ignoring for this discussion any envelope protection functions.) The elevator actuators may be capable of generating more force than required to get the surfaces to the command limits, but they are not allowed to. At low speeds the command limits are such that full elevator travel is achievable. At higher speeds control law limits are chosen to balance between (on the low end) elevator displacement needed to achieve pitch control power to meet maneuver requirements and (on the high end) deflections that would generate higher structural loads than necessary. This scheme allows the elevator limits to be tailored to provide the pitch control power needed, but no more so that the structure can be optimized for minimum weight. This is one of the ways in which FBW control is able to deliver improved performance. The story is always a little more complicated than one might at first think. |
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