Boeing 737 MAX - software wouldn't fix faulty airframe

nsaspook

Joined Aug 27, 2009
6,885
To quote one comment that I agree with:
The world has about 40 years of flying "unstable" aircraft since digital fly-by-wire was designed into aircraft in the late 1970's (e.g., F-117, B-2, just to name 2 examples). This is simply the commercial aircraft industry adopting it. So if one is surprised, they haven't been paying attention.
The problem is fault-tolerant design, not a 'Faulty' Airframe.
 

Thread Starter

MrChips

Joined Oct 2, 2009
20,161
I see red flags everywhere.
The problem and solution is not of an engineering nature.
The problem is about corporate interests and putting economics ahead of passenger safety.

In the long haul, this fiasco is going to cost Boeing much more than what they would have spent had they done the right thing in the first place.
 

WBahn

Joined Mar 31, 2012
25,217
Article written by Gregory Travis, a veteran software engineer and experienced, instrument-rated pilot.
Notice that one thing pointedly lacking in his credentials is anything related to aeronautical engineering. Being an "experienced, instrument-rated pilot" (or having flown 757 simulators) hardly qualifies.

Many airliners are designed with a goal of neutral stability and rely on augmentation systems to make them stable. Loss of those systems make the aircraft difficult to fly. Many military aircraft take that significantly further and are negatively stable and loss of the augmentation systems make them impossible to fly. It's been this way for decades. Small aircraft, like his Cessna, are positively stable and, in most situations, will recover themselves to a wings-level attitude if you just release the controls.
 
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Thread Starter

MrChips

Joined Oct 2, 2009
20,161
Notice that one thing pointedly lacking in his credentials is anything related to aeronautical engineering. Being an "experienced, instrument-rated pilot" (or having flown 757 simulators) hardly qualifies.

Many airlines are design with neutral stability and rely on augmentation systems to make them stable. Loss of those systems make the aircraft difficult to fly. Many military aircraft take that significantly further and are negatively stable and loss of the augmentation systems make them impossible to fly. It's been this way for decades. Small aircraft, like his Cessna, are positively stable and, in most situations, will recover themselves to a wings-level attitude if you just release the controls.
True. But Boeing intentionally sold the modified 737 MAX as the same 737. They avoided having to retrain pilots for economic reasons.
 

crutschow

Joined Mar 14, 2008
24,295
A few things I'm aware of they did very wrong:
  • Added the MCAS system without emphasising the nature of the change (it's right there in the middle of the pilots manual :rolleyes:) and not having the pilots trained to understand it (because they wanted to be able to say the pilots didn't need retraining from the standard 737).
  • Allowing the MCAS system to generate so much downward trim that it couldn't be corrected by pulling up on the yoke.
  • Not automatically disabling the MCAS when the pilot pulled up on the yoke.
  • Making some safety features, such as a light to show when the MCAS was active, optional and extra cost.
  • Not grounding the plances, retraining the pilots, and/or modifying the system after the first accident where the MCAS system was suspected.
I think Boeing is up for some huge liability for those two crashes.
 

TechWise

Joined Aug 24, 2018
64
Certainly here on the UK we love a good public enquiry costing £50 gazillion pounds. If the manufacturer is at fault I don't think it will end well for them here.
 

nsaspook

Joined Aug 27, 2009
6,885
True. But Boeing intentionally sold the modified 737 MAX as the same 737. They avoided having to retrain pilots for economic reasons.
Who is they?

Boeing doesn't pay to retrain pilots. The Air Carriers that buy Boeing planes do. Boeing designed the flight software to make it feel like the older 737 models because customers wanted it that way. Airbus does EXACTLY the same thing with airframes and software. I'm all for Boeing being held responsible for what they did but lets be fact based in the responsibility.

https://airfactsjournal.com/2019/03/can-boeing-trust-pilots/
Because the new MAX version of the 737 has heavier engines and other changes, Boeing added a system that under certain conditions of airspeed, CG location and weight, automatically moves the pitch trim to modify stick force. The pilot who is hand flying feels this as though he is pulling on the yoke and would naturally reduce pull force to lower the nose and angle of attack (AOA).

In the non-aviation media, this system is being called everything from new, to radical, to untested. In reality, nearly all airplanes larger than a basic four-seat piston single use some sort of device to alter the forces a pilot feels while maneuvering the airplane.
...
What Boeing is doing is using the age-old concept of using the human pilots as a critical element of the system. Before fly-by-wire (FBW) came along, nearly all critical systems in all sizes of airplanes counted on the pilot to be a crucial part of the system operation.

The certification concept for relying on the human involves identification of a failure, and a reaction time. The way it works is that the pilot must be able to recognize the failure, then take three seconds to analyze what is wrong, and then take corrective action before the airplane flies into a critical condition.
Though the pitch system in the MAX is somewhat new, the pilot actions after a failure are exactly the same as would be for a runaway trim in any 737 built since the 1960s. As pilots we really don’t need to know why the trim is running away, but we must know, and practice, how to disable it.

The problem for Boeing, and maybe eventually all airplane designers, is that FBW avoids these issues. FBW removes the pilot as a critical part of the system and relies on multiple computers to handle failures.
 
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visionofast

Joined Oct 17, 2018
68
ehh...I've always felt that BBC news website publishes most of air crash reports in the world before they happen.maybe should ask the reasons from them before :cool:
 

Ylli

Joined Nov 13, 2015
891
  • Allowing the MCAS system to generate so much downward trim that it couldn't be corrected by pulling up on the yoke.
  • Not automatically disabling the MCAS when the pilot pulled up on the yoke.
These^^ There should be no automated system that the pilots can not override with simple control inputs. Then make sure the people flying the planes are actually *pilots* and not just automated system operators.
 

WBahn

Joined Mar 31, 2012
25,217
If this true then it is the end of Boeing.
Then why wasn't it the end of Boeing when there were multiple incidents (seven, I believe), including two crashes that killed everyone on board, back in the early 1990's due to a fault in the design of the rudder actuator?
These^^ There should be no automated system that the pilots can not override with simple control inputs. Then make sure the people flying the planes are actually *pilots* and not just automated system operators.
Not practical. Even on small aircraft the pilot can't override everything. If you have a plane with a constant-speed prop you can only dial in the desired RPM and the system automatically adjusts the propeller pitch to maintain it. The pilot has no direct control over the propeller pitch.

Keep in mind that anytime you provide an override, you reduce the reliability of the system commensurately since you are making it more complicated and subject to a longer list of things that can go wrong. You also quickly move into the realm of the pilot having too many knobs and buttons to dink around with, which inevitably slows reaction time because that many more possible courses of action have to be assessed before making a decision.
 

spinnaker

Joined Oct 29, 2009
7,837
Then why wasn't it the end of Boeing when there were multiple incidents (seven, I believe), including two crashes that killed everyone on board, back in the early 1990's due to a fault in the design of the rudder actuator?


Not practical. Even on small aircraft the pilot can't override everything. If you have a plane with a constant-speed prop you can only dial in the desired RPM and the system automatically adjusts the propeller pitch to maintain it. The pilot has no direct control over the propeller pitch.
That was a simple fix, A rudder actuator as I recall. If this indeed is an airframe design issue the fix is going to be way more complicated. That is unless pilots and passengers are willing to live with the fact it is going to take software to keep the plane in the air (assuming there is an actual software fix for this).
 

nsaspook

Joined Aug 27, 2009
6,885
...
That is unless pilots and passengers are willing to live with the fact it is going to take software to keep the plane in the air (assuming there is an actual software fix for this).
Pilots and passengers live with it every day, what we can't tolerate is buggy software. Life critical software keeps all modern aircraft flying.
 

Thread Starter

MrChips

Joined Oct 2, 2009
20,161
Who is they?

Boeing doesn't pay to retrain pilots. The Air Carriers that buy Boeing planes do. Boeing designed the flight software to make it feel like the older 737 models because customers wanted it that way. Airbus does EXACTLY the same thing with airframes and software. I'm all for Boeing being held responsible for what they did but lets be fact based in the responsibility.

https://airfactsjournal.com/2019/03/can-boeing-trust-pilots/
Air Carriers vs Boeing

It works both ways. Boeing made it a selling point to not have to retrain pilots. Air Carriers liked that because it saved them money and persuaded them to purchase the 737 MAX. Ultimately it is Boeing's responsibility to ensure flight worthiness of the aircraft.

Ultimately, it will be paying air travelers who decide on the fate of Boeing.
 
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