re: 737max crashes in Ethiopia. Killing 157

Boeing CEO Muilenburg Issues Statement on Ethiopian Airlines Flight 302 Accident Investigation

quote:

---

Boeing Chairman, President and CEO Dennis Muilenburg issued the following statement regarding the report from Ethiopian Transport Minister Dagmawit Moges today.

First and foremost, our deepest sympathies are with the families and loved ones of those onboard Ethiopian Airlines Flight 302.

Boeing continues to support the investigation, and is working with the authorities to evaluate new information as it becomes available. Safety is our highest priority as we design, build and support our airplanes. As part of our standard practice following any accident, we examine our aircraft design and operation, and when appropriate, institute product updates to further improve safety. While investigators continue to work to establish definitive conclusions, Boeing is finalizing its development of a previously-announced software update and pilot training revision that will address the MCAS flight control law's behavior in response to erroneous sensor inputs. We also continue to provide technical assistance at the request of and under the direction of the National Transportation Safety Board, the U.S. Accredited Representative working with Ethiopian investigators.

In accordance with international protocol, all inquiries about the ongoing accident investigation must be directed to the investigating authorities.

---

Before the Lion Air crash, U.S. carriers flying the Max 8 were really fricking fortunate.

quote:

---

Both Boeing and the FAA were informed of the specifics of this story and were asked for responses 11 days ago, before the second crash of a 737 MAX last Sunday.

---

That one's going to hurt.

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.

---

If I’m reading it right. The system will tilt the horizontal stabilizer a few degrees each time it activated compounding the problem each time it resets.

Pretty big oversite by the engineers

BEA press release:

I think this will only get worse for Boeing, with the potential to get catastrophically worse.

From the WaPo: LINK

quote:

---

In October 2017, Brazilian regulators flew to Miami to test out the brand-new Boeing 737 Max 8. The team scrutinized the sleek new jetliner’s flight systems and soon published a list of over 60 operational changes, from landing systems to cockpit displays, that Brazilian pilots would need to learn.

Among the new features regulators said pilots would have to familiarize themselves with was the Maneuvering Characteristics Augmentation System, a safety system that could nose the plane downward if it sensed a potential stall.

---

quote:

---

In those same months, the Federal Aviation Administration was making its final revision to a 53-page report that would make up the backbone of Max 8 training guidelines for pilots across the United States and in almost every other country around the world.

It did not once mention the anti-stall system, according to a copy reviewed by The Post. In fact, the FAA report suggested pilots would experience nothing surprising in the cockpit of the new Max 8. In a section where FAA test pilots are supposed to list “unique handling or performance characteristics” of new planes, they remarked that there were none: “no specific flight characteristics,” the report read.

FAA’s publication of pilot training requirements for the Max 8 in the fall of 2017 was among the final steps in a multiyear approval process carried out under the agency’s now 10-year-old policy of entrusting Boeing and other aviation manufacturers to certify that their own systems comply with U.S. air safety regulations.

---

And here’s a good twitter thread re: Boeing’s software fix to a solution that isn’t a software problem to begin with: LINK

Again, to summarize the problem: in order to produce a “new” plane for a new marker as quickly and cheaply as possible, Boeing needed to put these big new modern engines on a 50 year-old 737 hull design they’re not compatible with. The result is a plane with poor physical design (engines too far up and front) that will push the plane’s nose too far up in certain situations, leading to a stall.

So the only way to get the thing certified is installing a computer to counter the poor physical design by automatically trimming the nose down without the pilot’s inout or knowledge when the instrument senses this situation. Problem is the instrument can sense this situation when that situation isn’t occurring, making the plane crash itself while the pilots are pulling up on the yoke with all their might (and this is another topic on its own: how the hell did Boeing approve a computer that set can trim so extreme as to negate and overpower all other input from the pilot?!?!)

But here’s the other deal: once you start limiting the MCAS activation, now you risk increasing the probability of the original problem it was meant to solve (nose too high/stalling)

My original point remains: this plane never should have been built. Pilots (and passengers) shouldn’t have to rely on software and sensors (especiallly non-redundant) to fix a problem inherent in the plane’s physical design, especially when that physical design flaw is due to stretching the limits of a hull design too far.

I fly a lot and have no fear of it, but I won’t be flying on a Max any time soon, if ever.

quote:

---

But here’s the other deal: once you start limiting the MCAS activation, now you risk increasing the probability of the original problem it was meant to solve (nose too high/stalling)

---

Not really. They’ll fix it. The way I read it the MCAS tilted the horizontal stabilizer 2.5 deg nose down. Once the pilots recovered the MCAS rearmed itself but didn’t reset the stabilizers back to neutral. So each time the plane neared a critical AOA the stabilizers moved another 2.5 deg eventually creating an unrecoverable nose down attitude unless the system was completely shut off.