By Andy Pasztor and Andrew Tangel
U.S. air-safety regulators have tentatively approved sweeping
software and pilot-training changes for Boeing Co.'s grounded 737
MAX jets, aimed at fixing problems with a suspect flight-control
system, according to internal government documents and people
familiar with the details.
The extensive revisions, these industry and government officials
said, will make the automated stall-prevention feature, called
MCAS, less aggressive and more controllable by pilots.
They also said the enhanced training, relying on self-guided
interactive instruction on laptops, highlights information about
when the system engages and how pilots can shut it off.
The changes amount to a reversal from major design and
engineering principles Boeing relied on when it developed the
stall-prevention system, which is suspected of causing the fatal
dive that killed 189 people on board a Lion Air 737 MAX in
Indonesia last October. A team of international crash investigators
also is looking into whether a similar problem led to the crash of
an Ethiopian Airlines plane less than five months later.
The Federal Aviation Administration has said it was working with
Boeing to develop and install a revised MCAS system based on
lessons learned from the Lion Air tragedy, but the extent of the
changes goes beyond what some industry officials expected. An FAA
spokesman declined to comment on specifics of the pending
changes.
Accident investigators have said the Lion Air plane got
erroneous information from one sensor that caused the
stall-prevention system to misfire, repeatedly pushing the nose of
the plane and ending at the maximum downward angle even though the
pilots were resisting. Authorities have said they see clear
similarities between that accident and the Ethiopian crash on March
10.
The modifications, officials said, create a gentler
stall-prevention feature, redesigned so it won't overpower other
cockpit commands or misfire based on faulty readings from a single
sensor. It is devised to automatically push the nose down only once
-- for no longer than 10 seconds -- if the aircraft is in danger of
stalling and losing lift.
The changes have been tentatively approved by FAA officials, the
people familiar with the details said, subject to final
ground-simulator checks and flight tests. They could be rolled out
to airlines' 737 MAX jets in the next few weeks.
A Boeing official said the new MAX software could still go
through revisions, and the timing of formal approval from the FAA
and foreign regulators remains fluid.
Even after the changes are fully implemented in the U.S.,
air-safety regulators in Canada and the EU are poised to conduct
their own evaluation of the new software as well as how the FAA
initially certified the plane to carry passengers. Those reviews
could take months, according to safety experts.
Among other changes, the revised software would rely on two
"angle of attack" sensors, rather than one, to measure the upward
or downward angle of the wings and nose in flight. If two sensors
send data differing by five degrees or more, MCAS wouldn't activate
at all, according to the officials briefed on the tentative
changes.
The cockpit crew on the Lion Air flight struggled against MCAS
-- using manual nose-up commands some two dozen times -- before
losing control and plunging into the Java Sea at more than 500
miles an hour. The interim accident report revealed a constant
20-degree difference between signals from the sensor on the
captain's side and those from the co-pilot's-side sensor.
On Saturday, Boeing said it has been "working diligently and in
close cooperation with the FAA on the software update," adding that
the company is "taking a comprehensive and careful approach to
design, develop and test the software that will ultimately lead to
certification" by regulators.
During the investigations of the two crashes, Boeing and the FAA
have faced criticism from pilot groups, airlines, politicians and
airlines for alleged lapses in the original MCAS design -- and for
failing to adequately inform aviators.
About a dozen pilots from U.S. and international carriers are
getting previews this weekend of the changes in the works, as well
as related manuals and training, according to the Boeing official.
"We want their feedback," this official said. "It's a
dialogue."
The group engaging in this weekend's preview of the changes
includes pilots from U.S. MAX operators: Southwest Airlines Co.,
American Airlines Group Inc. and United Continental Holdings Inc.,
a person familiar with the matter said. On Wednesday, this person
added, a larger group of more than 100 pilots from a broad cross
section of MAX operators are due at Boeing's 737 factory in Renton,
Wash., for a similar session.
Investigators in the Lion Air crash said faulty data transmitted
from a single sensor caused the MCAS system to assume the plane was
in danger of stalling. The warnings began during takeoff and
continued for much of the roughly 11-minute flight, apparently
confusing the pilots and creating a cascade of related warning
signals.
Under the new design, warning devices will alert crews if there
is a problem with sensors before takeoff or in flight, people
familiar with the redesign said. They said automated commands to
move a flight-control surface on the tail, called a horizontal
stabilizer, can be counteracted by pilot commands.
The changes will be standard on all 737 MAX aircraft, for which
Boeing has roughly 5,000 orders.
A draft FAA document spelling out the training revisions shows
pilots now will be specifically informed about "MCAS activation
thresholds," "flight crew alerts" and how to turn off the system by
flipping a single switch. Such details weren't highlighted in
earlier manuals or training materials circulated by Boeing.
FAA officials have determined the handing qualities of 737 MAX
jets will be close enough to earlier 737 models that pilots won't
need additional training in ground-based simulators, which is
expensive for airlines and disruptive to their schedules.
Alison Sider
and Robert Wall contributed to this article.
Write to Andy Pasztor at andy.pasztor@wsj.com and Andrew Tangel
at Andrew.Tangel@wsj.com
(END) Dow Jones Newswires
March 23, 2019 16:57 ET (20:57 GMT)
Copyright (c) 2019 Dow Jones & Company, Inc.
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