Investigators 'believe Ethiopian 737 Max's anti-stall system activated'

[brooklynite]

Source: The Guardian

Investigators believe Boeing’s controversial anti-stall system on its 737 Max aircraft was activated before Ethiopian Airlines flight ET302 crashed, killing all 157 people onboard, according to reports of a high-level safety briefing with US regulators.

The apparent findings, reported in the Wall Street Journal, would be the strongest indication yet that the same software problem could have contributed to the crash and that of Lion Air flight 610, which killed 189 people in Indonesia in October.

Investigators in the Lion Air case highlighted how pilots battled to keep the plane pointing upwards as the system automatically forced the nose down.

Ethiopian Airlines officials and Ethiopia’s transport minister have already said their 737 jet appeared to fly in a similar pattern to the Lion Air plane, both of which displayed erratic altitude during their short time in the air after takeoff.

Read more: https://www.theguardian.com/world/2019/mar/29/investigators-believe-anti-stall-activated-in-ethiopian-737-max-report-us-regulators-lawsuit-boeing

[democratisphere]

1. Looks like there are inherent flaws in the design of the 737 MAX

Jetliners that won't be fixed with a software upgrade.

[watoos]

2. Exactly,

it looks like the problem is with sensors.

[CentralMass]

3. Unstable flight characteristics due to power and cg changes with the jet engines.

The new larger more powerful jet engines that were used created unstable flight characteristics on take off. They tried to fix it with an unadvertised automated flight control system that hadn't been properly tested.

[democratisphere]

6. Right. It is an engine and aircraft compatibility problem that

gets back to halfassed engineering.

[Major Nikon]

9. All aircraft have instability characteristics

For some, like aerobatic and certain military aircraft, the instability is a feature, not a flaw. Transport category aircraft are designed to be more stable. It's entirely possible to design aircraft that are nearly impossible to stall or roll over, but that would present other problems which would be undesirable for the mission of these aircraft.

I don't know that they were so much as trying to fix a problem, or creating a solution in search of a problem. Aircraft stalling on climbout happens, but the reason is usually pilot inattention to where the aircraft is in the flight envelope and failure to take corrective actions.

[CentralMass]

11. My uneducated opinion is that they modified an old stable 737NG

Last edited Fri Mar 29, 2019, 02:30 PM - Edit history (1)

design, or at very least one who's flight characteristics were well known to many
pilots with a high number of hours in the plane, and made it unstable.

Note: this article concludes MCAS was the design flaw.

https://www.aviationcv.com/aviation-blog/2019/shocking-facts-boeing-737max-crash

However, from the article where it talks about Boeing scrambling to compete with Airbus on fuel efficiency.

"Airbus definitely complicated things for Boeing. They had to improvise quickly.

So, they did. To improve the fuel efficiency of their new jet, they not only introduced new winglets but Boeing also introduced new engines on the 737.

The CFM Leap-1B promised to be more efficient than the older CFM56-7B, which was on the 737NG. And indeed it is more efficient. However, it is also much bigger. It weighs more and it is bigger in size.

Because of its bigger size, Boeing had to change the mounting point of the engine. In short, they put them further forward and much higher on the wings. But the different mounting point made the Boeing 737 MAX prone to a stall. The engine positions on the wings forced the nose of the aircraft to go up.

But the further mounted engines were not the flaw. Nor was the bigger size. Boeing had to one-up Airbus somehow.

MCAS was the problem. The same software, which supposedly had to prevent the aircraft from stalling."

The article goes on to discuss MCAS and it flaws. But back to the design. Would Boeing if not pressured to get a more fuel efficient plane out the door have slapped some honker engines on an exiting design thst nade it more stall prone then the original ? Or would they have designed one that placed the wing/engine mounting to avoid making it stall prone rather the fixing with an automated control system ?

[Major Nikon]

12. The original 737 design dates back to the 60's

This was back when transport jets had turbojet engines rather than turbofan engines. The former is much smaller in diameter. The 737 was originally designed to be low to the ground to more easily embark and disembark people and cargo at airports that didn't have jetways and scissor lifts. If you look at previous 737s, the engines are flat on the bottom to allow for clearance with modern turbofan engines. At some point when you start expanding the airframe the larger engines required are going to need a different mounting strategy. Regardless of where or how you mount the engines, you are going to create issues with flight control in various stages of flight.

It's important to remember that Airbus and Boeing have or at least had very different strategies for aircraft design. Airbus started using fly-by-wire technologies with the A320 and uses software to address pretty much all problems created by aerodynamic designs. Boeing uses a more traditional control cable to hydraulic actuator design at least for most of their aircraft prior to the 777. There's advantages and disadvantages to either approach.

[CaptainTruth]

4. Yes there are inherent flaws with the MCAS software, & there were bad sensors.

Problem is the software was written to only check 1 AoA sensor (the plane has 2). In those crashes that 1 sensor was bad, in one case reading 20 degrees different from the other sensor while the plane was taxiing for takeoff (black box data). The software didn't even check both sensors before takeoff to make sure they agreed with each other. The 747 has 3, software checks them all to make sure they agree within a certain tolerance. If one is reading out of range it's disregarded. Boeing deliberately decided to NOT do that on the Max 8.

From what I've seen the problems with the Max 8 can be fixed if they change the flight control software to work more like it does on their older planes. Of course, if the AoA sensor is a new design, that should be examined too.

[Major Nikon]

7. The other problem was pilots weren't trained on how to turn the system off if it malfunctions

Stick pushers have been on transport category aircraft for decades and they inevitably malfunction. The difference is pilots knew what they were, how they operated, and were trained on how to turn them off. None of that appeared to have happened here.

[efhmc]

8. I heard two Americans pilots relate how they had to override and correct

manually,

[Major Nikon]

5. If it's the software that caused the issue, then it can be fixed with a modification to the software

[Sneederbunk]

10. Ethiopian Airlines sending black box to France for analysis

rather than US speaks volumes.

[jmowreader]

13. Maybe so, but the BEA is a very good agency