Boeing Systemic Problems Continue

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digits_
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Re: Boeing Systemic Problems Continue

Post by digits_ »

L39Guy wrote: Sun May 05, 2019 3:46 pm
Daniel Cooper wrote: Sun May 05, 2019 3:32 pm Why would they design a manual trim wheel that doesn't have enough mechanical advantage to retrim the aircraft after a significant runaway?
You mean being able to manually trim while flying around at Vne (340 kits+)? I don’t think that any aircraft can be manually trimmed at those types of speeds.
Huh? Why not? Quite some airplanes fly around at Vne quite often, especially during a descend. Why would an airplane not be trimmable at such a speed? Seems to be a big design issue if you can't trim it. Flying at Vne should be a non-event.
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Re: Boeing Systemic Problems Continue

Post by sportingrifle »

L39 guy...

Almost any airplane with powered stab tim...ie all Airbus and the B777, 787, can be trimmed "manually" at any airspeed from any trim position.

The problem with the 737 stab manual trim is that it is just the pilot winding on a wheel connected by hundreds of feet of cable to the stab jackscrew. (The stretch in the cable created a whole other issue as well, but that is irrelevant here.) So the force able to be applied is limited by the pilots strength. This is why it takes such a stupid number of turns on the wheel to achieve anything...it is done with mechanical advantage. Worse, on the NG (and I presume the Max) the trim wheels were reduced in size to make room for the big screen TV's in the panel. Just as they increased the span of the horizontal stab!

The trim system doesn't even come close to meeting modern JAR25 certification standards. It is there only because it got "grandfathered" in from an airplane that weighed half as much and had half the power. There is a pretty convincing case to require a powered, redundant re-design of the entire 737 stab trim system on not just the Max, but the NG as well.

Cheers Sportingrifle.
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Re: Boeing Systemic Problems Continue

Post by Raymond Hall »

Boeing waited until after Indonesian plane crash to inform FAA of 737 Max safety review

In the months after Boeing started delivering its new 737 Max jets in 2017, the company’s engineers discovered a problem: One of Boeing’s suppliers delivered flight control software that did not meet its requirements, Boeing disclosed Sunday.

It wasn’t until after a deadly plane crash involving related flight control software that the company informed regulators about the issue, which safety review committees from Boeing and the FAA determined was a “low-risk” problem, according to a statement on Boeing’s website.
The admission comes at a time when Boeing and the FAA face tremendous scrutiny over whether design flaws could have contributed to the deaths of hundreds of people in Indonesia and Ethiopia, where two 737 Max jets crashed in recent months under similar circumstances.
The disclosure could also feed into a broader inquiry over whether the process for designing and certifying commercial jets in the United States is flawed. The 737 Max was grounded worldwide in mid-March after the second crash brought the death toll to 346.

The software, which connects the airplane’s external sensors to pilots’ cockpit displays, is designed to alert pilots when sensors on either side of the plane are reporting conflicting measurements for the plane’s “angle of attack," a measure of how the plane approaches oncoming wind. Boeing included the alert as an optional feature in the 737 Max to alert pilots to potential equipment failures.

In its statement, Boeing said the planes can be operated safely without the alert.
“Neither the angle of attack indicator nor the AOA Disagree alert are necessary for the safe operation of the airplane," the statement reads. "They provide supplemental information only, and have never been considered safety features on commercial jet transport airplanes.”
Boeing’s statement Sunday comes a week after the Wall Street Journal reported that the angle-of-attack disagree alert was inoperable when Southwest Airlines and other carriers started flying the planes.

“The disagree alert was not operable on all airplanes because the feature was not activated as intended,” Boeing said in a statement last Monday.
When it discovered the software problem in 2017, Boeing assigned a committee to review the issue, which ultimately determined that the planes were safe to fly. But it wasn’t until November, 2018, after the Indonesian plane crash, that the company informed regulators at the Federal Aviation Administration. It is unclear whether Boeing would have been required to do so under FAA regulations. The company said it followed its standard operating procedures.

Later that month an investigative report from Indonesian authorities found that those sensors had malfunctioned in the final moments of the flight, and that pilots had struggled to overcome an automatic anti-stalling feature that nudged the plane’s nose downward.
The FAA review board found the alert to be a “low-risk” safety issue which would not render the plane unsafe to fly. An FAA spokesman said Sunday, however, that "Boeing’s timely or earlier communication with the operators would have helped to reduce or eliminate possible confusion.”

https://www.washingtonpost.com/business ... cac69824cf
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Re: Boeing Systemic Problems Continue

Post by L39Guy »

digits_ wrote: Sun May 05, 2019 4:37 pm
L39Guy wrote: Sun May 05, 2019 3:46 pm
Daniel Cooper wrote: Sun May 05, 2019 3:32 pm Why would they design a manual trim wheel that doesn't have enough mechanical advantage to retrim the aircraft after a significant runaway?
You mean being able to manually trim while flying around at Vne (340 kits+)? I don’t think that any aircraft can be manually trimmed at those types of speeds.
Huh? Why not? Quite some airplanes fly around at Vne quite often, especially during a descend. Why would an airplane not be trimmable at such a speed? Seems to be a big design issue if you can't trim it. Flying at Vne should be a non-event.
Manually trimming at Vne with the trim at near full nose down trim? Why would one ever get that far out of trim at that airspeed? Perhaps I should have clearer. Basically in trim at Vne with only small trim applications, perhaps.
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Re: Boeing Systemic Problems Continue

Post by L39Guy »

sportingrifle wrote: Sun May 05, 2019 5:47 pm L39 guy...

Almost any airplane with powered stab tim...ie all Airbus and the B777, 787, can be trimmed "manually" at any airspeed from any trim position.

The problem with the 737 stab manual trim is that it is just the pilot winding on a wheel connected by hundreds of feet of cable to the stab jackscrew. (The stretch in the cable created a whole other issue as well, but that is irrelevant here.) So the force able to be applied is limited by the pilots strength. This is why it takes such a stupid number of turns on the wheel to achieve anything...it is done with mechanical advantage. Worse, on the NG (and I presume the Max) the trim wheels were reduced in size to make room for the big screen TV's in the panel. Just as they increased the span of the horizontal stab!

The trim system doesn't even come close to meeting modern JAR25 certification standards. It is there only because it got "grandfathered" in from an airplane that weighed half as much and had half the power. There is a pretty convincing case to require a powered, redundant re-design of the entire 737 stab trim system on not just the Max, but the NG as well.

Cheers Sportingrifle.
You are quite correct. Please note my above comment about Vne+being grossly out of trim and note also that the B767/777/787 backup trim is with electric motors.

Apart from the MAX accidents where the pilots failed to use the manual, electric trim to keep the aircraft in trim (and override MCAS), the B737 trim system, ancient by modern standards, has served the industry well. I am aware of no accidents as a result of it.
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Re: Boeing Systemic Problems Continue

Post by L39Guy »

L39Guy wrote: Sun May 05, 2019 11:23 pm
digits_ wrote: Sun May 05, 2019 4:37 pm
L39Guy wrote: Sun May 05, 2019 3:46 pm
You mean being able to manually trim while flying around at Vne (340 kits+)? I don’t think that any aircraft can be manually trimmed at those types of speeds.
Huh? Why not? Quite some airplanes fly around at Vne quite often, especially during a descend. Why would an airplane not be trimmable at such a speed? Seems to be a big design issue if you can't trim it. Flying at Vne should be a non-event.
Manually trimming at Vne with the trim at near full nose down trim? Why would one ever get that far out of trim at that airspeed? Perhaps I should have been clearer. Basically in trim at Vne with only small trim applications, perhaps.
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Re: Boeing Systemic Problems Continue

Post by Raymond Hall »

From today's New York Times:

Simultaneously, Boeing is shaping a public relations strategy to reach passengers. Although the final media plan is still in the works, Boeing will not be relying solely on its executives to win back the public’s trust — a recognition that its leadership has lost some good will.
The company and airlines agree that the chief executive, Mr. Muilenburg, as the face of a company under intense scrutiny, may not be the most effective messenger. Instead, the initial plan calls for pilots to play a major role in the campaign.
“We think a key voice in all of this will be the pilots for our airlines, and their voice is very important,” Mr. Muilenburg said on Boeing’s earnings call last month. “That bond between the passenger and the pilot is one that’s critical, and so we’re working with our airline customers and those pilot voices to ensure that we can build on that going forward.”

Airline executives in the United States are eager for the Max to return to service and for Boeing to succeed. But many are privately frustrated with the company’s handling of the crisis, according to three people briefed on the matter. They believe that Boeing has badly mismanaged the public response to the crashes, and are irked that the public relations blitz will fall to their pilots.
Pilots, too, are reluctant to become brand ambassadors for Boeing, which barely interacted with them before the Lion Air crash last October, the first of the two deadly accidents.

In part, the reluctance stems from Boeing’s mixed messaging. Despite having said “we own it,” Mr. Muilenburg has not acknowledged that anything was wrong with the design of the 737 Max, saying that the design process followed standard procedures.

https://www.nytimes.com/2019/05/08/busi ... e=Homepage
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Re: Boeing Systemic Problems Continue

Post by pianokeys »

sportingrifle wrote: Sun May 05, 2019 5:47 pm L39 guy...

Almost any airplane with powered stab tim...ie all Airbus and the B777, 787, can be trimmed "manually" at any airspeed from any trim position.

The problem with the 737 stab manual trim is that it is just the pilot winding on a wheel connected by hundreds of feet of cable to the stab jackscrew. (The stretch in the cable created a whole other issue as well, but that is irrelevant here.) So the force able to be applied is limited by the pilots strength. This is why it takes such a stupid number of turns on the wheel to achieve anything...it is done with mechanical advantage. Worse, on the NG (and I presume the Max) the trim wheels were reduced in size to make room for the big screen TV's in the panel. Just as they increased the span of the horizontal stab!

The trim system doesn't even come close to meeting modern JAR25 certification standards. It is there only because it got "grandfathered" in from an airplane that weighed half as much and had half the power. There is a pretty convincing case to require a powered, redundant re-design of the entire 737 stab trim system on not just the Max, but the NG as well.

Cheers Sportingrifle.
Yeah good luck to the poor sole who has to push his chair back, bring out that dinky handle from the wheel and crank it 3000 times when youre -2G over in a dive thanks to come computer issue Boeing couldnt get right.
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Re: Boeing Systemic Problems Continue

Post by Raymond Hall »

L39Guy wrote: Mon Apr 29, 2019 7:57 am The Turkish accident at Schipol was the result of a single radar altimeter input into the autothrottle; when the single source thought it was at zero feet it retarded the thrust levers, the speed decayed and the aircraft stalled, despite three pilots being in the flight deck. Boeing then modified the system to take two inputs.
Those who cannot remember the past are condemned to repeat it. ... George Santayana
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Re: Boeing Systemic Problems Continue

Post by Raymond Hall »

Having reflected on all of the above... I still have a fundamental problem with this issue. Namely, hands and feet. Situational awareness. Needle, ball, airspeed. The Ethiopian accident occurred in day VFR conditions. Despite what the technology was doing, commanding the auto systems to input a response, was there not a way for someone, in the loop, to say, "NO!" — and to regain control of the aircraft?

Apparently the thrust system was responding to a fault indicating a stall, which, combined with the pitch down-commanded attitude led the aircraft to rapidly increase speed, imposing tremendous loads on the flight controls. As part of the attempted recovery, did the pilots disengage the auto thrust and reduce the thrust to idle?
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Re: Boeing Systemic Problems Continue

Post by L39Guy »

There is no interaction between the thrust system and the stall warning system - this is not like the Airbus when the speed is at alpha floor and the power goes to max. In both fatal accidents, the crew did not do the Unreliable Airspeed (UAS) memory checklist which includes disconnecting the autopilot (if it was on) and autothrust, setting an attitude and power setting (10 degrees/80%). In both of those cases the engines were at take-off power (94% in the case of Ethiopian) and the aircraft was flying around at Vne (~340 kts), making manually trimming the aircraft virtually impossible.

Contrast those two cases with the Lion Air incident the day before the Lion Air fatal accident where the crew did the UAS drill after take-off, controlled the speed of the aircraft (needle, ball, airspeed, etc) and were able to control the aircraft, shut off the stabilizer trim and manually trim the aircraft. Indeed, they flew to the destination (1 1/2 hours) with unreliable airspeed and manual trim (i.e. trim wheel with the crank handle).

So this begs the question: how is it that incident crew recognized a UAS (long before MCAS was present), shut the magic off, managed the aircraft (i.e. flew the aircraft) and were able to manage the MCAS but the accident crews were not able to even do the UAS drill, let alone the runaway stab trim drill.

To me, this points to a training issue with respect to flying in general and the B737 in particular.
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Re: Boeing Systemic Problems Continue

Post by yycflyguy »

Raymond Hall wrote: Sun May 12, 2019 11:11 pm Having reflected on all of the above... I still have a fundamental problem with this issue. Namely, hands and feet. Situational awareness. Needle, ball, airspeed. The Ethiopian accident occurred in day VFR conditions. Despite what the technology was doing, commanding the auto systems to input a response, was there not a way for someone, in the loop, to say, "NO!" — and to regain control of the aircraft?

Apparently the thrust system was responding to a fault indicating a stall, which, combined with the pitch down-commanded attitude led the aircraft to rapidly increase speed, imposing tremendous loads on the flight controls. As part of the attempted recovery, did the pilots disengage the auto thrust and reduce the thrust to idle?
The AT is not in any way related to the MCAS. It's been pointed out several times that the pilots did not fully complete the memory items for the Runaway Trim despite what Ethiopian told the media in the first days post accident. They did not disengage the AT. The thrust remained at take off power increasing the aerodynamic forces exponentially.

At AC we did not have AOA indications until after the Lion Air accident. Boeing is guilty of selling safety features.

The AD put out to operators should have already been known by Boeing operators. The lack of corrective action by the crew does not absolve Boeing for hiding the system completely from AOM descriptions and training nor does it absolve the FAA for essentially allowing Boeing to self certify another B737 that is nothing like a NG as far as W&B, engines, flight envelop and flying characteristics.
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Re: Boeing Systemic Problems Continue

Post by Raymond Hall »

Boeing says 737 Max update is being held up by FAA questions

Regulator has asked the aerospace giant how pilots interact with flight controls and displays

Boeing [says] that its update for the 737 Max software has been completed.

The U.S. regulator has asked Boeing to provide more details about “how pilots interact with the airplane controls and displays in different flight scenarios,” the company said in a statement Thursday. A spokesman for the FAA confirmed the agency is asking about pilot interaction on the 737 Max but declined to provide more information about the review process or how long it is expected to take.

“This process will take as long as necessary to ensure the aircraft is returned to service safely,” FAA spokesman Gregory Martin said.

https://www.washingtonpost.com/business ... e02a6a78n
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Re: Boeing Systemic Problems Continue

Post by Rezy »

Raymond Hall wrote: Sun May 12, 2019 11:11 pm As part of the attempted recovery, did the pilots disengage the auto thrust and reduce the thrust to idle?
Looking at the FDR, this likely would have killed them sooner. Reducing thrust would have lowered the airspeed. With the higher airspeed the more lift the wings create to offset the negative lift of the horizontal stabilizer (which was stuck in a nose down trim condition). The slower the airplane flies, with a nose down trim, the harder it is to stay in the air because the elevators are less effective.
Although the UAS drill has been mentioned lots, no evidence has been shown that it would have prevented either accidents at all.
The only thing the crew could have done was use the manual electric trim to center and then hit the cutout switches.
Flying slower would have killed them sooner.
Theory of Flight 101.
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Last edited by Rezy on Thu May 16, 2019 5:32 pm, edited 1 time in total.
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Re: Boeing Systemic Problems Continue

Post by Rezy »

L39Guy wrote: Tue Apr 30, 2019 3:42 pm
It all started with an Unreliable Airspeed (which includes the false warning) then, once the flaps were up and in manual flight, the Stab Trim Runaway. Two emergencies, both with recognized procedures.

The additional flying skills that would have helped would have been:
  • autothrottle - off
    set 10 degrees pitch
    set 80% power
    (these are part of the NNC
    with or without doing the NNC, someone should have been flying the airplane, and this includes
    manage the speed, instead the speed got up to max velocity of 340 Kts, which made manual trimming nearly impossible
    trim the aircraft, to maintain an in trim condition, with large bursts of trim, not timid, little tickles of the trim switch
There are other airmanship issues that I think we can all learn lessons about too:
  • with either problem, you are not going anywhere. Land the aircraft immediately
    if the problem stops, stay in that configuration and don't change configuration back to one that causes the issue to reappear
    know your emergencies
I don’t think we agree on the sequence of events and are getting confused in our discussion.
After getting the stall warning at rotation, the first action taken was to turn the autopilot on. Which was likely an attempt to prevent MCAS from running away as, according to the Boeing letter, it only operates in manual mode. Having solved the MCAS, because the autopilot came on, the crew decided to bring the flaps up. Why not? Autopilot is on and that means MCAS is off. Now when the autopilot turns off and the nose drops, resulting in max elevator force to keep the airplane in the air - the only thing that gave them a fight chance once they reached this point was airspeed. Airspeed allowed the elevator more force, allowed the wings to produce more lift, and thrust to pitch the nose up (slightly). While this was happening the only question that is really fair to ask, in my opinion, is why they didn’t manually use the electric trim to center the stabilizer and then hit the cutout switches.
I think for the most part we are in agreement, you’re just talking more about the first 60s and I’m talking about the last 60s.

Also to note, Boeing never mentions that leaving the flaps down prevents MCAS in their letter, how would these guys have know that? The only info they had to disable MCAS was to turn on the autopilot, which they did, and then it turned off.
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Re: Boeing Systemic Problems Continue

Post by L39Guy »

Rezy wrote: Thu May 16, 2019 5:27 pm
L39Guy wrote: Tue Apr 30, 2019 3:42 pm
It all started with an Unreliable Airspeed (which includes the false warning) then, once the flaps were up and in manual flight, the Stab Trim Runaway. Two emergencies, both with recognized procedures.

The additional flying skills that would have helped would have been:
  • autothrottle - off
    set 10 degrees pitch
    set 80% power
    (these are part of the NNC
    with or without doing the NNC, someone should have been flying the airplane, and this includes
    manage the speed, instead the speed got up to max velocity of 340 Kts, which made manual trimming nearly impossible
    trim the aircraft, to maintain an in trim condition, with large bursts of trim, not timid, little tickles of the trim switch
There are other airmanship issues that I think we can all learn lessons about too:
  • with either problem, you are not going anywhere. Land the aircraft immediately
    if the problem stops, stay in that configuration and don't change configuration back to one that causes the issue to reappear
    know your emergencies
I don’t think we agree on the sequence of events and are getting confused in our discussion.
After getting the stall warning at rotation, the first action taken was to turn the autopilot on. Which was likely an attempt to prevent MCAS from running away as, according to the Boeing letter, it only operates in manual mode. Having solved the MCAS, because the autopilot came on, the crew decided to bring the flaps up. Why not? Autopilot is on and that means MCAS is off. Now when the autopilot turns off and the nose drops, resulting in max elevator force to keep the airplane in the air - the only thing that gave them a fight chance once they reached this point was airspeed. Airspeed allowed the elevator more force, allowed the wings to produce more lift, and thrust to pitch the nose up (slightly). While this was happening the only question that is really fair to ask, in my opinion, is why they didn’t manually use the electric trim to center the stabilizer and then hit the cutout switches.
I think for the most part we are in agreement, you’re just talking more about the first 60s and I’m talking about the last 60s.

Also to note, Boeing never mentions that leaving the flaps down prevents MCAS in their letter, how would these guys have know that? The only info they had to disable MCAS was to turn on the autopilot, which they did, and then it turned off.
First, turning the autopilot on for either UAS (which is what was present for the first few minutes) is not the checklist procedure nor is it for a stall, if they thought they were stalled. But they tried the autopilot at 400 ft (minimum autopilot engagement altitude) as I suspect that is how they fly each and every day. The autopilot would not stay on, that is clear in the preliminary report. Fine.

But if they were really thinking that they had an MCAS event going on, then why raise the flaps as MCAS is not active with the flaps extended either, particularly if the autopilot will not engage?

It is true that speed is life, however too much speed is a problem as the control forces increase exponentially with increasing speed, all other things being equal. If you are above the stall speed and motoring around at maneouvering speed (roughly 220 kts clean), going 340 knots adds no extra value but it makes flight control forces for an out-of-trim stabilizer impossible to handle manually.

They did use electric trim but only in small bursts, according the preliminary report. That just wasn't going to cut it as a long trimming period was required much like one uses when flaps are being retracted or extended. I suspect that they did not do this is because they probably have never flown the aircraft manually where they actually had to trim the aircraft. The policies at most of these carriers is autopilot on at 400 ft on departure (long before any flap retraction and acceleration requiring manual trim) and autopilot off at 1000 ft. 500 ft, 200 ft or not at all on landing (after the deceleration and flap extension). Friends of mine that fly in Asia and Africa tell me that is the policy and as a result they have no manually flying skills, like managing the airspeed.
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Re: Boeing Systemic Problems Continue

Post by corethatthermal »

A circuit labelled MCAS would have easily prevented this alongside training on the system before the 1st accident. With a CB labelled MCAS , Boeing would have to tell the pilots MCAS existed and whether there must be type training ! Not having 2 sensors inputting allowed Boeing to do away with differences training SAD!!!
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Re: Boeing Systemic Problems Continue

Post by corethatthermal »

Looking at the large engine and its position relative to the small original hor. stab, this A/C must be reaching its min. design requirements at both ends of the travel OR did it already exceed allowable design parameters in the nose- down position ( le up ) ? Perhaps the A/C would lose all pitch authority above the min required speed and hence the MCAS. Like an A/C that is unable to be certified for stalls in certain configurations and therefore needs a stick pusher AND a stick shaker. Many A/C, many band-aid solutions come back to bite!
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Re: Boeing Systemic Problems Continue

Post by L39Guy »

corethatthermal wrote: Sun May 19, 2019 9:39 pm A circuit labelled MCAS would have easily prevented this alongside training on the system before the 1st accident. With a CB labelled MCAS , Boeing would have to tell the pilots MCAS existed and whether there must be type training ! Not having 2 sensors inputting allowed Boeing to do away with differences training SAD!!!
Since MCAS presents identical characteristics to a Stab Trim Runaway, doing this checklist including turning off the stab trim, per the NNC, would have achieved the same result.

It is also important to note that the Lion Air crew the day before with the same aircraft and issue flew the aircraft to destination (1 1/2 hours away) with manual trim (i.e. with the stab trim switches off). They seemed to get it right.
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Re: Boeing Systemic Problems Continue

Post by L39Guy »

corethatthermal wrote: Sun May 19, 2019 10:03 pm Looking at the large engine and its position relative to the small original hor. stab, this A/C must be reaching its min. design requirements at both ends of the travel OR did it already exceed allowable design parameters in the nose- down position ( le up ) ? Perhaps the A/C would lose all pitch authority above the min required speed and hence the MCAS. Like an A/C that is unable to be certified for stalls in certain configurations and therefore needs a stick pusher AND a stick shaker. Many A/C, many band-aid solutions come back to bite!
The MAX had an issue of neutral stability at high angle of attack/g loading (in a turn); the FAR's state that aircraft shall have positive stability, i.e. the angle of attack would decrease without any input. MCAS, like stick pushers in other aircraft, is there to provide that stability.

Most aircraft have a band aid solution as reality is rarely the same as theory. As an example, look at all that stuff hanging off the Beech 1900D, look at the vortex generators on the wings of many aircraft, there is a stall strip on the leading edge inboard of the engines on the B737 NG, etc. Did you know that the B747-800 has a band aid software solution to fix an aileron flutter issue.
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