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An aerial photo shows Boeing 737 Max airplanes parked on the tarmac at a factory in Renton, Wash., on March 21, 2019.

Lindsey Wasson/Reuters

Airplane maker Boeing Co. on Wednesday outlined proposed updates to the software system and new pilot-training requirements for its 737 Max aircraft, which are grounded worldwide after two unexplained crashes killed 346 passengers and crew.

Chicago-based Boeing gave no timeline for the changes and did not say when the global fleet of 371 Max planes will resume flying.

“We will be making fleet updates in the form of software updates. We will be deploying training and returning to flight will be at the regulators’ discretion,” Mike Sinnett, Boeing’s vice-president of product development, told reporters on a conference call on Wednesday morning.

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In both recent crashes of the new model, there are reports the pilots fought – and lost – a fight with the plane’s automated anti-stall system that points the nose toward the ground.

A Lion Air plane crashed into the Java Sea 12 minutes after takeoff last October, killing all 189 people on board. The Ethiopian Airlines crash on March 10 killed 157 people.

The software patches Boeing outlined on Wednesday for reporters and, later, 200 pilots and industry officials in Seattle, are intended to improve the crew’s control over an automated flight system known as the Maneuver Characteristics Augmentation System, or MCAS.

The planes in the two fatal crashes displayed similar flight profiles – steep dives and recoveries before the pilots apparently lost the ability to override the automated system. Both crews tried to return to the airport before crashing.

The safety improvements Boeing announced include allowing the MCAS system to gather data from two sensors to eliminate the chance of erroneous data activating the automatic control and making standard a warning feature that triggers when the sensors disagree. This warning system was previously available only to airlines that paid for it. Other changes include improved operators’ manuals, bulletins and computer-based training. The upgrades also ensure some automatic flight-control inputs do not exceed the pilot’s ability to override them.

Mr. Sinnett, who declined to answer questions about the crashes, said the updates are the result of “hundreds and hundreds of hours of desktop analysis and laboratory testing” and several test flights.

“In all cases, pilots continue to have the ability to manually override MCAS and manually control the aircraft,” he said.

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“All of us here at Boeing are deeply affected by the tragic loss of Lion Air and Ethiopian Airlines passengers and crew,” Mr. Sinnett said. “We’re going to do everything we can to make sure accidents like these never happen again. We’re working with customers and regulators around the world to restore faith in the industry and to reaffirm our commitment to safety and to earn the trust of the flying public.”

Tewolde GebreMariam, chief executive officer of Ethiopian Airlines, told the Associated Press this week that the training and manuals provided by Boeing and the U.S. Federal Aviation Administration might not have been enough to give pilots the ability to prevent the crash. In an interview before Boeing outlined the updates, he said it would be difficult for Boeing to restore trust in the planes.

Transport Minister Marc Garneau followed international actions and banned the 737 Max on March 13 from taking off, landing or travelling through Canadian airspace. He said the decision was based on information that the Ethiopian Airlines flight path resembled that of the Lion Air crash.

The FAA grounded the 737 Max hours later, but came under criticism for not doing so sooner. Most other major international regulators took the step a day or two after the March 10 Ethiopian crash.

Air Canada has parked its 24 Max aircraft while WestJet Airlines Ltd. has pulled its 13 from service. The moves spurred both airlines to suspend their financial guidance for this year, and threw into disarray the March break travel plans for thousands of Canadians.

Morgan Bell, a WestJet spokeswoman, said the Calgary-based carrier had pilot representation at the Boeing presentation on Wednesday, but that it is “premature” to speculate on when its planes might be updated with Boeing’s proposed changes.

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“Should we be directed by our regulators to implement any such changes or associated training, we will absolutely take the proper steps to do so,” Ms. Bell said.

Air Canada and Transport Canada did not respond to e-mailed questions.

Mr. Garneau has said Canada will conduct its own certification of the Max once Boeing has made the software changes required. The step is a departure for the approval process – Canada usually accepts the FAA’s certificate of safety.

During U.S. Senate hearings on Wednesday, FAA acting administrator Daniel Elwell defended the FAA’s practice of relying on aircraft makers to help certify their own planes for flight, saying it has worked safely decades. Shifting the agency away from self-certification, he said, would require 10,000 more employees and an additional US$1.8-billion a year to do all the work now performed by designated employees of the companies it regulates.

The 737 Max, launched in 1997, is an updated version of a narrow-body passenger jet first introduced in the 1960s. Boeing said there are 5,000 Max jets on order, making it a top seller. However, last week Garuda Indonesia became the first airline to publicly cancel its Max orders.

Meanwhile, investigators in Indonesia and Ethiopia continue to examine the wreckage and flight data recorders for causes of the crashes. The focus is expected to be on the planes’ MCAS systems.

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update on the way

Boeing said Wednesday that it has developed an

update to its automated anti-stall system called the

Maneuvering Characteristics Augmentation

System (MCAS)

MCAS is designed to prevent a stall, the loss of lift

that occurs when too little air is moving over the

wings. It was implemented to address the jet’s

changed balance after the planemaker installed

larger engines and moved them forward on its

new Max series aircraft.

How Boeing’s anti-stall sensor works

When the nose is level...

The angle of attack (AOA) sensor, which measures the

angle between the airflow and the wing, align with

oncoming airflow. The sensor tells MCAS when the wings

are losing airflow because the plane’s nose

is pointed too high.

Airflow

AOA sensor

When the nose is elevated...

The angle of attack rises and when it becomes too high,

the anti-stall system activates. MCAS then tilts the

horizontal stabilizer in the tail of the aircraft to

force the plane’s nose down restore airflow.

Horizontal

stabilizer

what’s new in the update

AOA sensor agreement

Unlike before, the flight control system will now

compare data from both AOA sensors. If there is a

discrepancy of more than 5.5 degrees between the

two with flaps retracted...

Both AOA sensors

5.5˚

Warning light

...the MCAS will not activate and a warning will

appear in front of the pilots on their Primary Flight

Display (PFD) instrument panel.

Primary Flight Display

Warning light

Manual control

The updated MCAS will only be able to

make one automated control input for

each elevated angle of attack event.

MCAS will not be able to move the

stabilizer more than can be counter

acted manually by the pilots.

The flight crew will still be able to re-take

manual control of the aircraft by using

inputs to the flight controls.

THE GLOBE AND MAIL, SOURCE: boeing; reuters;

graphic news

update on the way

Boeing said Wednesday that it has developed an

update to its automated anti-stall system called the

Maneuvering Characteristics Augmentation

System (MCAS)

MCAS is designed to prevent a stall, the loss of lift

that occurs when too little air is moving over the

wings. It was implemented to address the jet’s

changed balance after the planemaker installed

larger engines and moved them forward on its

new Max series aircraft.

How Boeing’s anti-stall sensor works

When the nose is level...

The angle of attack (AOA) sensor, which measures the

angle between the airflow and the wing, align with

oncoming airflow. The sensor tells MCAS when the wings

are losing airflow because the plane’s nose

is pointed too high.

Airflow

AOA sensor

When the nose is elevated...

The angle of attack rises and when it becomes too high,

the anti-stall system activates. MCAS then tilts the

horizontal stabilizer in the tail of the aircraft to

force the plane’s nose down restore airflow.

Horizontal

stabilizer

what’s new in the update

AOA sensor agreement

Unlike before, the flight control system will now

compare data from both AOA sensors. If there is a

discrepancy of more than 5.5 degrees between the

two with flaps retracted...

Both AOA sensors

5.5˚

Warning light

...the MCAS will not activate and a warning will

appear in front of the pilots on their Primary Flight

Display (PFD) instrument panel.

Primary Flight Display

Warning light

Manual control

The updated MCAS will only be able to

make one automated control input for

each elevated angle of attack event.

MCAS will not be able to move the

stabilizer more than can be counter-

acted manually by the pilots.

The flight crew will still be able to re-take

manual control of the aircraft by using

inputs to the flight controls.

THE GLOBE AND MAIL, SOURCE: boeing; reuters;

graphic news

update on the way

Boeing said Wednesday that it has developed an update to its automated anti-stall

system called the Maneuvering Characteristics Augmentation System (MCAS)

MCAS is designed to prevent a stall, the loss of lift that occurs when too little air is

moving over the wings. It was implemented to address the jet’s changed balance after

the planemaker installed larger engines and moved them forward on its new Max

series aircraft.

How Boeing’s anti-stall sensor works

When the nose is level...

When the nose is elevated...

The angle of attack (AOA) sensor, which

measures the angle between the airflow

and the wing, align with oncoming airflow.

The sensor tells MCAS when the wings are

osing airflow because the plane’s nose

is pointed too high.

The angle of attack rises and when it

becomes too high, the anti-stall system

activates. MCAS then tilts the horizontal

stabilizer in the tail of the aircraft to

force the plane’s nose down

restore airflow.

Airflow

Horizontal

stabilizer

AOA sensor

what’s new in the update

AOA sensor agreement

Warning light

Unlike before, the flight control system will

now compare data from both AOA sensors. If

there is a discrepancy of more than 5.5 degrees

between the two with flaps retracted...

...the MCAS will not activate and a

warning will appear in front of the

pilots on their Primary Flight Display

(PFD) instrument panel.

Both AOA sensors

Primary Flight Display

5.5˚

Warning light

Manual control

The updated

MCAS will only

be able to make

one automated

control input for

each elevated

angle of attack

event.

MCAS will not

be able to

move the

stabilizer more

than can be

counteracted

manually by

the pilots.

The flight crew

will still be able

to re-take

manual control of

the aircraft by

using inputs to

the flight controls.

THE GLOBE AND MAIL, SOURCE: boeing; reuters; graphic news

With files from The Associated Press

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