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re: 737max crashes in Ethiopia. Killing 157
Posted on 3/17/19 at 9:46 pm to When in Rome
Posted on 3/17/19 at 9:46 pm to When in Rome
quote:
The original Boeing document provided to the FAA included a description specifying a limit to how much the system could move the horizontal tail — a limit of 0.6 degrees, out of a physical maximum of just less than 5 degrees of nose-down movement.
quote:
After the Lion Air Flight 610 crash, Boeing for the first time provided to airlines details about MCAS. Boeing’s bulletin to the airlines stated that the limit of MCAS’s command was 2.5 degrees.
quote:
One current FAA safety engineer said that every time the pilots on the Lion Air flight reset the switches on their control columns to pull the nose back up, MCAS would have kicked in again and “allowed new increments of 2.5 degrees.” “So once they pushed a couple of times, they were at full stop,” meaning at the full extent of the tail swivel, he said.
quote:
“A hazardous failure mode depending on a single sensor, I don’t think passes muster,” said Lemme. Like all 737s, the MAX actually has two of the sensors, one on each side of the fuselage near the cockpit. But the MCAS was designed to take a reading from only one of them...Alternatively, the system could have been designed to check that the angle-of-attack reading was accurate while the plane was taxiing on the ground before takeoff, when the angle of attack should read zero
The fix seems like it should have been there from the start - Training on it including how to disable, in manual, and using both existing sensors instead of just 1 for something that that was given unlimited authority. Lion Air AOA sensors were 20 degrees different on runway & one being off was probably not as high as a concern for them not knowing about MCAS.
quote:
According to a detailed FAA briefing to legislators, Boeing will change the MCAS software to give the system input from both angle-of-attack sensors. It will also limit how much MCAS can move the horizontal tail in response to an erroneous signal. And when activated, the system will kick in only for one cycle, rather than multiple times. Boeing also plans to update pilot training requirements and flight crew manuals to include MCAS.
This post was edited on 3/17/19 at 11:04 pm
5
Posted on 3/18/19 at 9:54 am to dallastigers
This article was posted in another thread yesterday; copying over to this thread.
WSJ
WSJ
quote:It will be interesting to see what regulatory action, if any, comes as a result of this investigation.
Federal prosecutors and Department of Transportation officials are scrutinizing the development of Boeing Co.’s [BA -2.11%] 737 MAX jetliners, according to people familiar with the matter, unusual inquiries that come amid probes of regulators’ safety approvals of the new plane.
A grand jury in Washington, D.C., issued a broad subpoena dated March 11 to at least one person involved in the 737 MAX’s development, seeking related documents, including correspondence, emails and other messages, one of these people said. The subpoena, with a prosecutor from the Justice Department’s criminal division listed as a contact, sought documents to be handed over later this month.
It wasn’t immediately clear whether the Justice Department’s probe is related to scrutiny of the Federal Aviation Administration by the DOT inspector general’s office, reported earlier Sunday by The Wall Street Journal and that focuses on a safety system that has been implicated in the Oct. 29 Lion Air crash that killed 189 people, according to a government official briefed on its status. Aviation authorities are looking into whether the anti-stall system may have played a role in last week’s Ethiopian Airlines crash, which killed all 157 people on board.
This post was edited on 3/18/19 at 9:54 am
Posted on 3/18/19 at 9:59 am to dallastigers
quote:Yeah, the ability for the system to reset itself every time the pilot responded should probably never have been a feature of the system.
The new anti-stall system on the Boeing 737 MAX forced the nose of Lion Air JT610 down 26 times in 10 minutes before the pilots lost control and the plane dived into the sea.
Posted on 3/18/19 at 11:02 am to dallastigers
quote:
But the MCAS was designed to take a reading from only one of them...Alternatively, the system could have been designed to check that the angle-of-attack reading was accurate while the plane was taxiing on the ground before takeoff, when the angle of attack should read zero
Poor.
For something that important, the sensor really should have been checked (automatically) when they were on the ground. Just a simple (sensor1 - sensor 2) and use the one that shows read zero if there was a difference.
I understand why you'd want to feed just one signal in, but for something that vital you'd want to verify that primary instrument was working properly and be able to seamlessly shift to the other if it wasn't.
Posted on 3/18/19 at 12:48 pm to dallastigers
Do you know what time scale the x axis is on this?
Posted on 3/18/19 at 1:12 pm to dallastigers
Looking at that flight data graph, I see some things that perhaps one of our resident pilots and discuss.
1. It seems that the pilots stick shaker began at the same time the plane lifted off the ground.
2. Why would the pilot retract the flaps and then extend the flaps during an indicated stall? I thought the planes configuration should not be changed until the plane is stabilized?
3. Had they left the flaps extended, mcas would have never turned on.
1. It seems that the pilots stick shaker began at the same time the plane lifted off the ground.
2. Why would the pilot retract the flaps and then extend the flaps during an indicated stall? I thought the planes configuration should not be changed until the plane is stabilized?
3. Had they left the flaps extended, mcas would have never turned on.
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