The option is to have AOA displayed and have an AOA miscompare warning annunciation on the PFD. This miscompare warning has been inop since 2017, but Boeing didn't tell this to the operators, and planned to slide the fix in during a planned later software update.
Quote:
Originally Posted by DarkSideMoon
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https://www.nytimes.com/2019/03/21/b...es-charge.html
“Standard 737 Max planes are not equipped with a so-called angle of attack indicator or an angle of attack disagree light. The indicator will continue to cost airlines extra, but the light won’t.
Standard 737 Max planes are not equipped with a so-called angle of attack indicator or an angle of attack disagree light. The indicator will continue to cost airlines extra, but the light won’t.CreditCreditRuth Fremson/The New York Times
By Hiroko Tabuchi and David Gelles
March 21, 2019
As the pilots of the doomed Boeing jets in Ethiopia and Indonesia fought to control their planes, they lacked two notable safety features in their cockpits.
One reason: Boeing charged extra for them.
For Boeing and other aircraft manufacturers, the practice of charging to upgrade a standard plane can be lucrative. Top airlines around the world must pay handsomely to have the jets they order fitted with customized add-ons.
Sometimes these optional features involve aesthetics or comfort, like premium seating, fancy lighting or extra bathrooms. But other features involve communication, navigation or safety systems, and are more fundamental to the plane’s operations.
Many airlines, especially low-cost carriers like Indonesia’s Lion Air, have opted not to buy them — and regulators don’t require them.
Now, in the wake of the two deadly crashes involving the same jet model, Boeing will make one of those safety features standard as part of a fix to get the planes in the air again.
It is not yet known what caused the crashes of Ethiopian Airlines Flight 302 on March 10 and Lion Air Flight 610 five months earlier, both after erratic takeoffs. But investigators are looking at whether a new software system added to avoid stalls in Boeing’s 737 Max series may have been partly to blame. Faulty data from sensors on the Lion Air plane may have caused the system, known as MCAS, to malfunction, authorities investigating that crash suspect.
Federal prosecutors are investigating the development of the Boeing 737 Max jet, according to a person briefed on the matter. As part of the federal investigation, the F.B.I. is also supporting the Department of Transportation’s inspector general in its inquiry, said another person with knowledge of the matter.
The Justice Department said that it does not confirm or deny the existence of any investigations. Boeing declined to comment on the inquiry.
The jet’s software system takes readings from one of two vanelike devices called angle of attack sensors that determine how much the plane’s nose is pointing up or down relative to oncoming air. When MCAS detects that the plane is pointing up at a dangerous angle, it can automatically push down the nose of the plane in an effort to prevent the plane from stalling.
Debris from Ethiopian Airlines Flight 302, which crashed on March 10. The angle of attack features could have alerted the pilots if a new software system was malfunctioning.
Boeing’s optional safety features, in part, could have helped the pilots detect any erroneous readings. One of the optional upgrades, the angle of attack indicator, displays the readings of the two sensors. The other, called a disagree light, is activated if those sensors are at odds with one another.
Boeing will soon update the MCAS software, and will also make the disagree light standard on all new 737 Max planes, according to a person familiar with the changes, who spoke on condition of anonymity because they have not been made public. Boeing started moving on the software fix and the equipment change before the crash in Ethiopia.
The angle of attack indicator will remain an option that airlines can buy. Neither feature was mandated by the Federal Aviation Administration. All 737 Max jets have been grounded.
“They’re critical, and cost almost nothing for the airlines to install,” said Bjorn Fehrm, an analyst at the aviation consultancy Leeham. “Boeing charges for them because it can. But they’re vital for safety.”
Earlier this week, Dennis A. Muilenburg, Boeing’s chief executive, said the company was working to make the 737 Max safer.
“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,” he said in a statement.
Add-on features can be big moneymakers for plane manufacturers.
In 2013, around the time Boeing was starting to market its 737 Max 8, an airline would expect to spend about $800,000 to $2 million on various options for such a narrow-body aircraft, according to a report by Jackson Square Aviation, an aircraft leasing firm in San Francisco. That would be about 5 percent of the plane’s final price.
Boeing charges extra, for example, for a backup fire extinguisher in the cargo hold. Past incidents have shown that a single extinguishing system may not be enough to put out flames that spread rapidly through the plane. Regulators in Japan require airlines there to install backup fire extinguishing systems, but the F.A.A. does not.
“There are so many things that should not be optional, and many airlines want the cheapest airplane you can get,” said Mark H. Goodrich, an aviation lawyer and former engineering test pilot. “And Boeing is able to say, ‘Hey, it was available.’”
But what Boeing doesn’t say, he added, is that it has become “a great profit center” for the manufacturer.
The three American airlines that bought the 737 Max each took a different approach to outfitting the cockpits.
American Airlines, which ordered 100 of the planes and has 24 in its fleet, bought both the angle of attack indicator and the disagree light, the company said.
Southwest Airlines, which ordered 280 of the planes and counts 36 in its fleet so far, had already purchased the disagree alert option, and it also installed an angle of attack indicator in a display mounted above the pilots’ heads. After the Lion Air crash, Southwest said it would modify its 737 Max fleet to place the angle of attack indicator on the pilots’ main computer screens.
United Airlines, which ordered 137 of the planes and has received 14, did not select the indicators or the disagree light. A United spokesman said the airline does not include the features because its pilots use other data to fly the plane.
Boeing is making other changes to the MCAS software.
When it was rolled out, MCAS took readings from only one sensor on any given flight, leaving the system vulnerable to a single point of failure. One theory in the Lion Air crash is that MCAS was receiving faulty data from one of the sensors, prompting an unrecoverable nose dive.
In the software update that Boeing says is coming soon, MCAS will be modified to take readings from both sensors. If there is a meaningful disagreement between the readings, MCAS will be disabled.
Incorporating the disagree light and the angle of attack indicators on all planes would be a welcome move, safety experts said, and would alert pilots — as well as maintenance staff who service a plane after a problematic flight — to issues with the sensors.
The alert, especially, would bring attention to a sensor malfunction, and warn pilots they should prepare to shut down the MCAS if it activated erroneously, said Peter Lemme, an avionics and satellite-communications consultant and former Boeing flight controls engineer.
“In the heat of the moment, it certainly would help,” he said.”
https://aviationweek.com/commercial-...sue-found-2017
“WASHINGTON—New questions are being raised over the development and oversight of the Boeing 737 MAX after revelations the manufacturer knew about a mis-configured angle of attack disagree annunciator alert message on the aircraft in 2017 but did not fix it or tell operators about the problem until after last October’s crash of a 737 MAX 8—the first of two to strike the model in five months.
Boeing on May 5 clarified that within “several months” after MAX deliveries began in May 2017, it discovered that most of its 737 MAXs were being delivered without angle-of-attack (AOA) disagree alert message being activated as intended. It determined the issue was not a safety risk, however, and planned to address it as part of routine flight control software updates. The revelation adds more context to why the amber AOA Disagree alert messages, meant to tell pilots of a discrepancy between the aircraft’s two AOA sensors, have only been active on MAX aircraft equipped with a package of options.
“The Boeing design requirements for the 737 MAX included the AOA disagree alert as a standard, standalone feature, in keeping with Boeing’s fundamental design philosophy of retaining commonality with the 737NG,” Boeing said. “In 2017, within several months after beginning 737 MAX deliveries, engineers at Boeing identified that the 737 MAX display system software did not correctly meet the AOA disagree alert requirements. The software delivered to Boeing linked the AOA disagree alert to the AOA indicator, which is an optional feature on the MAX and the NG. Accordingly, the software activated the AOA disagree alert only if an airline opted for the AOA indicator.”
Boeing’s statement does not discuss whether the software was developed to its specifications, or whether the vendor introduced the error. Boeing’s statement does not name the vendor, but it is Collins Aerospace. Collins referred all questions to Boeing.
After it discovered the issue, Boeing said it followed its “standard process for determining the appropriate resolution of such issues,” including a review with “multiple company subject-matter experts.” The review “determined that the absence of the AOA disagree alert did not adversely impact airplane safety or operation,” Boeing said. “Accordingly, the review concluded, the existing functionality was acceptable until the alert and the indicator could be delinked in the next planned display system software update.”
Boeing’s senior management was not involved in the review, and neither Boeing’s senior leadership nor FAA were made aware of the issue until after the Oct. 29, 2018, crash of Lion Air Flight 610.
The AOA sensors provide key data to the MAX’s maneuvering characteristics augmentation system (MCAS) flight control law that is the focus of two fatal 737-8 accidents—Lion Air flight 610 and the Mar 10 crash of Ethiopian Airlines flight 302—in which all 346 people were killed and that have left the MAX fleet grounded.
In each accident, faulty data sent by one AOA sensor told the aircraft’s flight control computer that its nose was too high, causing MCAS to command horizontal stabilizer nose down trim. Preliminary reports on each accident suggest the pilots were not able to diagnose the failure quickly enough.
The original MCAS is programmed to command nose down trim if the AOA data shows the angle of attack is too high. Pilots can counter it in two ways: with electric trim input or via the manual trim wheel. Electric trim input resets MCAS, meaning faulty AOA data would trigger it again after a 5 sec. delay. In both accident sequences, the pilots countered with electric trim, setting up the MCAS’s cyclical activation.
Boeing’s safety analysis determined that crews would diagnose an unwanted MCAS activation as stabilizer runaway, and would follow the appropriate checklist, which includes de-powering the stabilizer trim motors by turning off the trim cutout switches, leaving the manual trim wheels as the only elevator trim inputs. The Ethiopian crew toggled off the cutout switches, but could not manually trim the aircraft at the relatively high indicated airspeed, so they turned on the trim cutout switches, which set the stage for MCAS to re-engage.
Neither Lion Air nor Ethiopian Airlines had the optional AOA disagree indicator package. The accident sequences would have triggered AOA disagree alerts, adding it to several that activated, including a stick-shaker stall warning.
Following the Lion Air accident, Boeing convened a “safety review board” (SRB) to revisit whether the AOA Disagree issue was a safety risk. “That SRB confirmed Boeing’s prior conclusion that it did not,” Boeing said. “Boeing shared this conclusion and the supporting SRB analysis with the FAA.”
Addressing reporters following a Boeing shareholder meeting Apr. 29, Boeing CEO Dennis Muilenburg downplayed the significance of the AOA Disagree alert’s role in delivering key information to pilots. “It’s not something that drives pilot action,” he said. “It’s not something that we designed in as a primary flight display in the flight deck of a commercial airplane. What pilots care about are things like altitude, airspeed, heading, pitch and roll. That’s what they fly. Those indicators are in the flight deck today. Airspeed and altitude in particular are the relevant items around these two [accidents].”
Even if the absence of the AOA Disagree lights is not linked to either accident, the issue adds more questions to the MAX’s development, and how much airlines knew about changes from the 737NG. MCAS was not on the NG, and most pilots didn’t know it existed until after the Lion Air accident.
Since just after the Lion Air accident, Boeing has described the AOA Disagree as an available option on the MAX, which was accurate. It was not until Apr. 29 that it explained the AOA Disagree’s status as an option was a mistake—it was supposed to be standard, as it is on the NG. Six days later, it acknowledged that it has known about this problem since mid-2017.
Boeing is updating MCAS, using both AOA sensors to prevent the system from acting on a single faulty sensor. The changes also will limit MCAS’s authority, in part by removing its ability to reset itself and potentially fire again based on faulty AOA data when the crew provides electric stabilizer trim input to counter it.
In addition, Boeing will make both the AOA disagree alerts and AOA indicator standard on all MAXs, including offering free modifications for aircraft already delivered.
Note: This story has been updated from the original version published May 5. It includes additional details and clarifications on MCAS's operation and the AOA Disagree alert's intended function.”