Boeing 737 Max 8 Problems

"The planemaker said last week it would submit final paperwork for the revamp to the Federal Aviation Administration by March 29 to make the system -- known as MCAS -- less aggressive in pushing down a plane’s nose, and to add redundancy so that it’s less likely to activate when other systems malfunction. Now Boeing says the update won’t be ready until the “coming weeks.”

An issue with integrating the software fix and the plane’s existing flight-control architecture came to light as Boeing did a final audit of the upgrade, according to a person briefed on the work. Ensuring that MCAS will perform as desired while not interfering with existing flight controls isn’t expected to be a significant challenge said the person, who wasn’t authorized to speak about the work and asked not to be identified."


Bloomberg - Are you a robot?




What was the MCAS fix in January, 2019?


Why didn't the MCAS disengage when pilots followed the Boing protocol to cancel the MCAS?


How did the Nose Down self-generated computer commands override manual control input?


How many versions of the Boeing 737 need to be upgraded?



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"A pair of switches on the center console between the pilots will turn off the automatic trim and a mechanism, new on the 737 MAX, known as the Maneuver Characteristics Augmentation System, or MCAS, that is suspected of playing a role in both disasters.

TRAINING MATERIAL ‘NOT CLEAR’

But pilots would have needed to know that MCAS existed, that it had unusual power to force the plane down and that “a hard pull on the yoke” would no longer turn off the automatic trim that uses MCAS, John Hansman, an aeronautics professor at MIT, said in an interview.

“That wasn’t clear to the pilots flying the airplane,” Hansman said. “The training material was not clear on that.”


Change to 737 MAX controls may have imperiled planes, experts say - Reuters





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"Now it is readying for regulatory approval a final software update and training package to address an anti-stall system known as MCAS that played a role in both nose-down crashes.

A draft report by an FAA-appointed board of pilots, engineers and other experts concluded that pilots only need additional computer-based training to understand MCAS, rather than simulator time. The public has until April 30 to make comments."


"the MAX computer training, which originally involved a one-hour iPad course, should include videos of simulator sessions showing how MCAS works along with demonstrations of other cockpit emergencies such as runaway stabilizer, a loss of control that occurred on both doomed flights.

APA also called for recurring training on simulators that includes scenarios like those experienced by the Lion Air and Ethiopian Airlines pilots, in addition to computer training.

“When pilots visually experience the failure modes and then apply them, the lesson is cemented in their minds,” APA wrote."


Pilots demand better training if Boeing wants to rebuild trust in 737 MAX - Reuters







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Found some movies on YouTube of showing a pilot in a Boeing 737 Max 8 simulator, using the switch on the ack of the center console, to turn off the automatic Trim control, and manually wheeling back the rotors on the side of the center console, to level off the tail trim tabs. Not sue that is the whole story on the final fix.



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Typos from last post, MCAS "Switches are on the Back of the center console to turn off MCAS..."



"Boeing has developed an MCAS software update to provide additional layers of protection if the AOA sensors provide erroneous data. The software was put through hundreds of hours of analysis, laboratory testing, verification in a simulator and two test flights, including an in-flight certification test with Federal Aviation Administration (FAA) representatives on board as observers.

The additional layers of protection include:
Flight control system will now compare inputs from both AOA sensors. If the sensors disagree by 5.5 degrees or more with the flaps retracted, MCAS will not activate. An indicator on the flight deck display will alert the pilots.
If MCAS is activated in non-normal conditions, it will only provide one input for each elevated AOA event. There are no known or envisioned failure conditions where MCAS will provide multiple inputs.
MCAS can never command more stabilizer input than can be counteracted by the flight crew pulling back on the column. The pilots will continue to always have the ability to override MCAS and manually control the airplane.

These updates reduce the crew’s workload in non-normal flight situations and prevent erroneous data from causing MCAS activation.

We continue to work with the FAA and other regulatory agencies on the certification of the software update."


Boeing: The 737 MAX MCAS Software Enhancement


Views 188


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Boeing 737 Max simulator problems, Breaking News Thread.

Boeing admits flaws in 737 MAX simulator software after crashes



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Gladiator said:

Boeing 737 Max simulator problems, Breaking News Thread.

Boeing admits flaws in 737 MAX simulator software after crashes



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Click to expand...

If the simulation is good people should have been crashing in simulation also.

AOA disparity warning light cover up, Breaking News thread:

Boeing didn’t plan to fix 737 MAX warning light until 2020




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You Tube video explaining the stbilizer jackscrew motor, and MCAS Disengagement procedures on a 737 Max simulator.

YouTube


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"“Government pilots discovered that a microprocessor failure could push the nose of the plane toward the ground,” CNN reports, adding that “it is not known whether the microprocessor played a role in either crash.”


This appears to be distinct from the problem with the MCAS system, which is believed to have been critical to both previous crashes. In these events, the planes — which relied on data from a single, potentially faulty angle-of-attack sensor, without a backup sensor — drove the aircraft directly into the ground, despite pilot attempts to override it. The implication of the CNN report is that the microprocessor failure is separate from the AOA sensor failure, but there’s nothing to identify what subsystem the chip is in, or whether there are redundant parts that are supposed to take over the functionality in the event of a failure.

Once again, this will mean additional delays for the 737 Max’s return to the skies. Reuters reports that Boeing will not conduct a recertification flight until July 8, best-case, but that the delays could stretch on for several weeks more. There’s a bit of uncertainty on whether a hardware change might be required. CNN states: “Boeing engineers are trying to determine if the microprocessor issue can be fixed by reprogramming software or if replacing the physical microprocessors on each 737 Max aircraft may be required."

New 737 Max Flaw Keeps Jet Grounded as Past Boeing Problems Surface - ExtremeTech

Sometimes news reports are more reliable than info released by the FAA.


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How do you make a redundant worm gear? If the worm gear jams, how can there be redundancy?

The 737 Max Tail Trim is operated by a worm gear.