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737 MAX - Safe or Unsafe?

Old 03-16-2019, 08:36 AM
  #81  
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Originally Posted by Klsytakesit View Post
It will come down to certification basis.
Boeing, at the request of SWA, Alaska Airlines and to a varying degree the big Three, rushed out a response to the A320/321 NEO.
In doing so they discovered that a big under-slung engine on a longer pylon created deleterious effect on maneuver margins near the edge of the envelope. Lacking any type of an intelligent maneuver-assistive FCC they strapped one on to essentially a manual system. And broke all their own rules about critical Flight Control design. Single source, no fail-safe, no comparator, no false-input control. Nothing but a QRH. Having pushed up against the limits of simple common type, they and their airline partners convinced the FAA that these changes were simple and not only did not require training but really only mechanics need know of them. No need to point it out to pilots as it would just confuse them. Nothing should happen and if it does it will be hidden under the general Runaway Stabilizer Trim QRH...
Bingo. Forget about MCAS potato and Americans waxing poetic about foreigners not being able to TP-stall recover an airliner like they're reliving their USAF UPT glory days. The quoted above is the real issue, and what needs to be talked about more. Boeing wanted to get away with not incurring certification costs of a new type by frankensteining the 73 certificate. It is therefore poetic justice they would get bent over questions of a sub-system allowed in under the very certification-stretching they've been mining for decades in the first place. About time their cost-cutting and 737 back alley plastic surgery clinic was finally exposed.

They got Capone under the lesser tax evasion, so frankly I couldn't care less whether the foreign case studies were 100% MCAS/sensor related or not. Win's a win. This ought to effectively wash out their gains in choosing to not design the "composite 757", to include accepting the certification costs a clean sheet design would normally incur.
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Old 03-16-2019, 08:43 AM
  #82  
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Originally Posted by PerfInit View Post
Interesting that the FAA’s B-737 Flight Standardization Board Report (FSB Report) does not identify any required Differences Training or Special Emphasis Items with respect to the MCAS system on the -Max vesus previous models?

www.fsims.faa.gov, under Publications, FSB Reports, Boeing.
The Brazilian certifying authority did identify it as a "B" category training item. What training GOL implemented I don't know but they must have thought it was not enough because they grounded their fleet voluntarily after the second incident.
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Old 03-16-2019, 08:43 AM
  #83  
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Originally Posted by hindsight2020 View Post
Bingo. Forget about MCAS potato and Americans waxing poetic about foreigners not being able to TP-stall recover an airliner like they're reliving their USAF UPT glory days. The quoted above is the real issue, and what needs to be talked about more. Boeing wanted to get away with not incurring certification costs of a new type by frankensteining the 73 certificate. It is therefore poetic justice they would get bent over questions of a sub-system allowed in under the very certification-stretching they've been mining for decades in the first place. About time their cost-cutting and 737 back alley plastic surgery clinic was finally exposed.

They got Capone under the lesser tax evasion, so frankly I couldn't care less whether the foreign case studies were 100% MCAS/sensor related or not. Win's a win. This ought to effectively wash out their gains in choosing to not design the "composite 757", to include accepting the certification costs a clean sheet design would normally incur.
Yep.

But Boeing (and airbus) did have good reason o extend their current narrow-bodies rather than do clean-sheet designs. There's lots of new technology looming which should be ready in a decade or so which will drastically improve economy, emissions, and carbon footprint. But it's radical enough to require a clean-sheet design, so if you spend the R&D on that now your new plane will likely be obsolete in ten years, and you won't have the R&D money to design the plane of the future.

Airbus had a big advantage... the bus is taller than the 73, so they could easily fit bigger fans under the wing to extend the economic life of their current product. Boeing had to jury-rig motor mounts, MCAS, build folding gear struts, etc.

Boeing also had to contend with keeping their modified product under a common type... they were already pushing the boundaries on that.

Tough for Boeing... the fact that the original 73 was designed for straight turbojets came back to haunt them.
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Old 03-16-2019, 08:56 AM
  #84  
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Originally Posted by Arrow50t View Post
I find the grounding of the 737 Max unjustified and believe the airplane is safe to fly.

case closed
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Old 03-16-2019, 12:31 PM
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Originally Posted by rickair7777 View Post
Yep.

Tough for Boeing... the fact that the original 73 was designed for straight turbojets came back to haunt them.
A common myth. The Pratt and Whitney JT8D was definitely a turbofan, albeit a low bypass one.
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Old 03-16-2019, 12:43 PM
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Originally Posted by N6279P View Post
A common myth. The Pratt and Whitney JT8D was definitely a turbofan, albeit a low bypass one.
Learned something new.
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Old 03-17-2019, 03:41 AM
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At least it sounded like a real jet vs a turbo weed eater.


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Old 03-17-2019, 02:17 PM
  #88  
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Originally Posted by pangolin View Post
MCAS I think was a good idea but poorly implemented.

First - it should be disabled and not activate if there's an airspeed disagree or any detected issue with AOA indicators. That's a simple fix. Frankly this system activating during such a circumstance is just exacerbating an already existing emergency.

Second - it should not be allowed to get to full nose down trim below a specific altitude - Boeing can decide what that altitude is but I'd say 10000 feet and certainly not 6000.

The purpose of MCAS is to help with stall recovery with high power settings. Tests could be performed to determine what the max nose down trim should be with full power, but I'm certain it's not FULL nose down trim. Limit it.

I think that this can be fixed and the fleet safely returned to service. I'm sure smarter people than me at Boeing have already considered what I'm proposing.



I think its pretty obvious the MCAS system as currently rolled out and implemented including not notifying airlines nor requiring any training for crews was poorly handled.


Second Adis Ababa airport is at an elevation over 7000 feet so your 6000' solution would not have helped, 10,000 maybe?



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Old 03-17-2019, 03:41 PM
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Interesting, if different, analysis. Link plus text below.

https://www.zerohedge.com/news/2019-...tware-engineer


The Best Analysis Of What Really Happened To The Boeing 737 Max From A Pilot & Software Engineer

Profile picture for user Tyler Durden
by Tyler Durden


The following tweets from Trevor Sumner, CEO of Perch Experience, of what really happened to the Boeing 737 Max, may be one of the best summaries of the events that led to the two recent airplane crashes, and also why Boeing's "software upgrade" response is a farce.


1of x: BEST analysis of what really is happening on the #Boeing737Max issue from my brother in law kammeyer, who’s a pilot, software engineer & deep thinker. Bottom line don’t blame software that’s the band aid for many other engineering and economic forces in effect.������


Some people are calling the 737MAX tragedies a #software failure. Here's my response: It's not a software problem. It was an

* Economic problem that the 737 engines used too much fuel, so they decided to install more efficient engines with bigger fans and make the 737MAX.

* Airframe problem. They wanted to use the 737 airframe for economic reasons, but needed more ground clearance with bigger engines.The 737 design can't be practically modified to have taller main landing gear. The solution was to mount them higher & more forward.

* Aerodynamic problem. The airframe with the engines mounted differently did not have adequately stable handling at high AoA to be certifiable. Boeing decided to create the MCAS system to electronically correct for the aircraft's handling deficiencies.


During the course of developing the MCAS, there was a

* Systems engineering problem. Boeing wanted the simplest possible fix that fit their existing systems architecture, so that it required minimal engineering rework, and minimal new training for pilots and maintenance crews.

The easiest way to do this was to add some features to the existing Elevator Feel Shift system. Like the #EFS system, the #MCAS relies on non-redundant sensors to decide how much trim to add. Unlike the EFS system, MCAS can make huge nose down trim changes.


On both ill-fated flights, there was a:

* Sensor problem. The AoA vane on the 737MAX appears to not be very reliable and gave wildly wrong readings. On #LionAir, this was compounded by a

* Maintenance practices problem. The previous crew had experienced the same problem and didn't record the problem in the maintenance logbook. This was compounded by a:

* Pilot training problem. On LionAir, pilots were never even told about the MCAS, and by the time of the Ethiopian flight, there was an emergency AD issued, but no one had done sim training on this failure. This was compounded by an:

* Economic problem. Boeing sells an option package that includes an extra AoA vane, and an AoA disagree light, which lets pilots know that this problem was happening. Both 737MAXes that crashed were delivered without this option. No 737MAX with this option has ever crashed.

* Pilot expertise problem. If the pilots had correctly and quickly identified the problem and run the stab trim runaway checklist, they would not have crashed.

Nowhere in here is there a software problem. The computers & software performed their jobs according to spec without error. The specification was just ****ty. Now the quickest way for Boeing to solve this mess is to call up the software guys to come up with another band-aid.

I'm a software engineer, and we're sometimes called on to fix the deficiencies of mechanical or aero or electrical engineering, because the metal has already been cut or the molds have already been made or the chip has already been fabed, and so that problem can't be solved.

But the software can always be pushed to the update server or reflashed. When the software band-aid comes off in a 500mph wind, it's tempting to just blame the band-aid.
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Old 03-17-2019, 03:55 PM
  #90  
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Originally Posted by CrowneVic View Post
Interesting, if different, analysis. Link plus text below.

https://www.zerohedge.com/news/2019-...tware-engineer


The Best Analysis Of What Really Happened To The Boeing 737 Max From A Pilot & Software Engineer

Profile picture for user Tyler Durden
by Tyler Durden


The following tweets from Trevor Sumner, CEO of Perch Experience, of what really happened to the Boeing 737 Max, may be one of the best summaries of the events that led to the two recent airplane crashes, and also why Boeing's "software upgrade" response is a farce.


1of x: BEST analysis of what really is happening on the #Boeing737Max issue from my brother in law kammeyer, who’s a pilot, software engineer & deep thinker. Bottom line don’t blame software that’s the band aid for many other engineering and economic forces in effect.������


Some people are calling the 737MAX tragedies a #software failure. Here's my response: It's not a software problem. It was an

* Economic problem that the 737 engines used too much fuel, so they decided to install more efficient engines with bigger fans and make the 737MAX.

* Airframe problem. They wanted to use the 737 airframe for economic reasons, but needed more ground clearance with bigger engines.The 737 design can't be practically modified to have taller main landing gear. The solution was to mount them higher & more forward.

* Aerodynamic problem. The airframe with the engines mounted differently did not have adequately stable handling at high AoA to be certifiable. Boeing decided to create the MCAS system to electronically correct for the aircraft's handling deficiencies.


During the course of developing the MCAS, there was a

* Systems engineering problem. Boeing wanted the simplest possible fix that fit their existing systems architecture, so that it required minimal engineering rework, and minimal new training for pilots and maintenance crews.

The easiest way to do this was to add some features to the existing Elevator Feel Shift system. Like the #EFS system, the #MCAS relies on non-redundant sensors to decide how much trim to add. Unlike the EFS system, MCAS can make huge nose down trim changes.


On both ill-fated flights, there was a:

* Sensor problem. The AoA vane on the 737MAX appears to not be very reliable and gave wildly wrong readings. On #LionAir, this was compounded by a

* Maintenance practices problem. The previous crew had experienced the same problem and didn't record the problem in the maintenance logbook. This was compounded by a:

* Pilot training problem. On LionAir, pilots were never even told about the MCAS, and by the time of the Ethiopian flight, there was an emergency AD issued, but no one had done sim training on this failure. This was compounded by an:

* Economic problem. Boeing sells an option package that includes an extra AoA vane, and an AoA disagree light, which lets pilots know that this problem was happening. Both 737MAXes that crashed were delivered without this option. No 737MAX with this option has ever crashed.

* Pilot expertise problem. If the pilots had correctly and quickly identified the problem and run the stab trim runaway checklist, they would not have crashed.

Nowhere in here is there a software problem. The computers & software performed their jobs according to spec without error. The specification was just ****ty. Now the quickest way for Boeing to solve this mess is to call up the software guys to come up with another band-aid.

I'm a software engineer, and we're sometimes called on to fix the deficiencies of mechanical or aero or electrical engineering, because the metal has already been cut or the molds have already been made or the chip has already been fabed, and so that problem can't be solved.

But the software can always be pushed to the update server or reflashed. When the software band-aid comes off in a 500mph wind, it's tempting to just blame the band-aid.
I have no further need to continue checking in on these threads now. Thank you. I must go find something more productive to do with myself now.
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