SoylentNews is people
SoylentNews
Initial Findings Put Boeing's Software at Center of Ethiopian 737 Crash:
At a high-level briefing at the Federal Aviation Administration on March 28, officials revealed "black box" data from Ethiopian Airlines Flight 302 indicated that the Boeing 737 MAX's flight software had activated an anti-stall feature that pushed the nose of the plane down just moments after takeoff. The preliminary finding officially links Boeing's Maneuvering Characteristics Augmentation System (MCAS) to a second crash within a five-month period. The finding was based on data provided to FAA officials by Ethiopian investigators.
The MCAS was partly blamed for the crash of a Lion Air 737 MAX off Indonesia last October. The software, intended to adjust the aircraft's handling because of aerodynamic changes caused by the 737 MAX's larger turbofan engines and their proximity to the wing, was designed to take input from one of two angle-of-attack (AOA) sensors on the aircraft's nose to determine if the aircraft was in danger of stalling. Faulty sensor data caused the MCAS systems on both the Lion Air and Ethiopian Airlines flights to react as if the aircraft was entering a stall and to push the nose of the aircraft down to gain airspeed.
On March 27, acting FAA Administrator Daniel Ewell told the Senate Commerce, Science, and Transportation Committee's aviation subcommittee that there had been no flight tests of the 737 MAX prior to its certification to determine how pilots would react in the event of an MCAS malfunction. He said that a panel of pilots had reviewed the software in a simulator and determined no additional training was required for 737-rated pilots to fly the 737 MAX.
What follows is from memory from what I've gleaned from reading several news accounts over the past few weeks. I am not a pilot, so take this with the proverbial $unit of salt.
The design of the MAX version of the Boeing 737 used a larger diameter engine so as to improve fuel economy. Because the original 737 was designed to be low to the ground to facilitate boarding (no jetways back then), it required the engines to be mounted forward and higher than in previous models. This introduced a change in the flight dynamics. Adding throttle in certain conditions would cause the plane to "nose up". Because of the shear size of the engine nacelles, this further increased the lift of the nose (more surface exposed at an angle to the air flow). This would cause further lift and would exacerbate the situation. Boeing wanted pilots to be able to fly the MAX without undergoing expensive retraining. How can they make a different aircraft behave like its predecessor, the 737-NG? The solution Boeing came up with was MCAS which — in certain circumstances — was designed to push the plane's nose back down. So much authority was provided to this adjustment, and its repeated application in some cases, that it could lead to driving the plane downward in spite of the pilot's efforts to maintain level flight. Complicating matters, there was no mention of MCAS in any of Boeing's training materials: pilots were not even aware it was there.
It would be easy to "armchair quarterback" Boeing's decisions. The airline industry was transitioning from its hub-and-spoke system (which favored larger planes) to having a greater number of direct (no layover) flights which favored smaller aircraft. In the meantime Airbus had come out with a new model of more efficient aircraft which fit this flight profile. Boeing could have come up with a clean-slate design for a new aircraft, but that would require several years from design to construction to certification. They elected to modify the 737, instead. As long as it was sufficiently similar (I'm waving my hands around a bit here), it could be sold based on the certification of its earlier models. So, they decided to modify the 737... but not too much so as to avoid the time-consuming recertification process.
I've heard it said, "The longest distance between two points is a shortcut." It is sad that this shortcut appears to have been responsible for two flights crashing shortly after takeoff and killing nearly 350 people.
(Score: 0) by Anonymous Coward on Sunday March 31 2019, @04:48AM (2 children)
I'm right here. They are the pilot, they need to know the memory items, period. Now, I'm not saying Boeing did nothing wrong, but the accident wasn't Boeing's fault either; the pilots could have prevented it with the memory items. Yes, repeated trims would be disorienting, especially if the annunciator or EGPWS goes off, but any failure of the trim system such that it adjusts itself beyond the inputs provided by the pilot (including the autopilot) is, by definition, a runaway trim situation. They had multiple minutes to get it under control, and they could have silenced the annunciator while doing so. Now sure, the EGPWS is a bit more to deal with as a distraction, but there are two pilots and either one could have hit the trim cutoff switch long before that became an issue.
Plus, to point out again. There was a third situation in the news from a third-world country where following the memory items did prevent a crash. Too bad only one pilot out of five was able to remember the 737 memory items during this third-world incidents.
(Score: 5, Informative) by choose another one on Sunday March 31 2019, @08:33AM
"one pilot out of five" ???
- you can't seat five in a 737 cockpit
- there were seven pilots in total, that we know of, who have faced erroneous MCAS, six failed to cope, one flight survived only because the jumpseat pilot (the extra one) had time to go get a book out and say "maybe try this"
- read AF447 report - 30+ crews known to have faced transient UAS in cruise on A330s with iced pitots, 30+ crews it was a non-event, one crew stalled into the ocean, and THAT WASN'T GOOD ENOUGH for safety levels the industry expects
But let's look beyond that.
- Boeing made an assumption about "pilots could have prevented it with the memory items".
- Did they or the airlines test that assumption with line crews? - I mean that's the sort of thing simulators are for, right?
- But MAX doesn't need simulator training... result: there are (effectively) NO max simulators out there, you fly the max after training on NG simulator, NG simulator does not have MCAS and cannot replicate this form of stab runaway, period
And further beyond:
- MAX test flights have been tracked above Renton, flight altitude profiles look like they are MCAS testing
- the altitude loss, WITH TEST PILOTS, is allegedly 2000-3000ft - maybe the test pilots don't know the memory items?
- Ethiopian flight only reached 1000ft (AGL), lose 2000ft when you are at 1000 and you end up with exactly the Ethiopian result
(Score: 2) by janrinok on Sunday April 07 2019, @07:09AM
https://www.bbc.com/news/business-47834556 [bbc.com]
https://edition.cnn.com/2019/04/04/world/ethiopian-airlines-crash-preliminary-report-intl/index.html [cnn.com]
I can understand your belief based upon your own experiences that the crashes were due to 'pilot error' from '3rd world airlines', but it seems those of us who had more inquiring minds had already seen through the blame game and realised that something rather more serious was at fault.
The initial findings clearly identified that the pilots took all the correct actions to regain control of the aircraft and, in particular, precisely followed the newly-issued advice from Boeing. The pilots actions did not prevent the crash from occurring. The company have admitted that there is something wrong and that they are responsible for correcting it.
It is probably good that you posted as AC, as your reputation here is now somewhat tarnished. Despite your claimed experience and knowledge, you were no better informed than anyone else on this site. You weren't there, you didn't know exactly what had happened, yet you continued to wave the Boeing flag and blame anyone or anything not American. You were wrong.