737 MAX Safety Tests Covering Increasingly Remote Failure Risks -- Update
August 02 2019 - 7:03PM
Dow Jones News
By Andy Pasztor
As Boeing Co. and safety regulators push to complete
long-awaited fixes for 737 MAX jets, testing has expanded to cover
increasingly unlikely emergencies including potential computer
failures pinpointed by overseas authorities, according to U.S.
government officials briefed on the details.
The broader risk analyses and simulator scenarios, some details
of which haven't been reported before, show the lengths to which
leaders of the Federal Aviation Administration, in coordination
with their foreign counterparts, are going to verify the safety of
the MAX fleet before allowing the planes to fly again.
Misfires of an automated flight-control system called MCAS led
to two fatal crashes in less than five months, taking 346 lives. A
package of fixes and training enhancements specifically targeting
MCAS was assembled and tested months ago. But since then, according
to the officials, 737 MAX reviews are delving into potential
hazards beyond the specific software that controls the MAX
feature.
The upshot, according to one person familiar with the details,
is that Boeing has opted to make the plane's overall flight-control
computer functions more redundant. Going forward, both of those
critical computers will be functioning on each MAX flight, versus
the original design that had them alternating between flights,
according to this person. The change was first reported by the
Seattle Times.
As part of the new focus, regulators also have shifted their
attention to the likelihood of pilots reacting as quickly as
anticipated to a range of extreme emergencies involving various
flight-control features. A portion of the ongoing testing and
analysis is delving into extremely remote but potentially
catastrophic problems that have a probability of less than one in
100 million flights. For initial certification of safety-critical
systems, regulators typically use a far tighter standard of roughly
one in a billion.
Specifically, the results of one sequence of tests requested by
European regulators and performed in a Boeing flight simulator
weeks ago, has extended the certification process by approximately
three more months, according to the government officials and others
familiar with the testing. The revised timetable means the jet,
which has been idled since March, likely won't resume commercial
service until at least early 2020, industry and government
officials have said.
A trio of FAA pilots climbed into Boeing's most advanced
simulator in a Seattle suburb in late June to replicate a
computer-chip failure that had never occurred in flight but could
result in strong, automated commands pushing down a plane's nose.
The failure mode that resulted in erroneous computer output was
similar, but not directly related, to MCAS misfires, according to
the government officials.
It took one of the pilots 16 seconds to identify and react to
the malfunction, significantly longer than current FAA
certification rules and safety guidelines permit, some of the
agency officials said. The upshot, they added, was a determination
that if an airline crew confronted such a problem -- even though
chances of it happening are extremely small -- the consequences
could be catastrophic.
Earlier this week, Ali Bahrami, the FAA's top safety official,
told a Senate subcommittee during a hearing that the June tests
"identified a very remote failure case," adding that FAA pilots
decided "the level of proficiency that is required to recover from
this event was exceptional" and could overwhelm average airline
crews.
That particular test was requested by the European Union
Aviation Safety Agency, according to one of those agency officials.
It's unusual for foreign regulators to make such requests, but the
MAX saga has upended the traditional relationship between EASA and
the FAA.
One of the simulator scenarios ended with the plane diving
uncontrollably toward the ground at about 400 miles an hour, said
another agency official familiar with the details.
When acting FAA chief Daniel Elwell was briefed on the results,
the officials said, he decided the potential risk had to be
addressed. The FAA has said it won't lift the grounding until all
safety issues, including questions by foreign regulators, are
conclusively resolved
Boeing also began re-examining the redundancy of the plane's
overall flight-computer system, according to some of the government
officials.
Boeing has said it expects to rectify all outstanding safety
issues through software changes. On Friday, a spokesman said
"safety is our priority as we continue to work with the FAA and
global regulators on software to address" the latest questions.
Write to Andy Pasztor at andy.pasztor@wsj.com
(END) Dow Jones Newswires
August 02, 2019 18:48 ET (22:48 GMT)
Copyright (c) 2019 Dow Jones & Company, Inc.
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