Could Knowledge of Undisclosed MCAS Have Saved Lion Air 610?

Could Knowledge of
Undisclosed MCAS Have Saved Lion Air 610?

By Rob Mark

Having spent more than a few decades in the cockpit, I thought
even I’d reached that plateau where I could claim I’d just
about seen it all … until this week’s admission by Boeing of an
– until now, unknown – automated AoA related stall-prevention
system called MCAS that, even when the aircraft is being hand
flown, could yank the control column away from an unsuspecting

Details are of course still sketchy, but I’m dumbfounded that
anyone at Boeing could be so certain of a computerized system
aboard the 737 Max 8, that they saw no need to mention its
existence to operators or pilots.


From Flying eNews, November 15, 2018 …

In what some pilots are calling an inconceivable moment in
flight operations and training, Boeing recently admitted the
existence of the maneuvering characteristics augmentation system
(MCAS), an angle of attack related stall prevention system that was
unknown to operators of the Boeing 737 Max 8 aircraft, like the one
flown last week by a Lion Air crew when it departed Jakarta
Indonesia. The Lion Air crew experienced an unexpected nose pitch
down shortly after takeoff as the aircraft was passing through
5,000 feet. Unable to recover from the event, all 189 people
aboard perished
in the crash that followed

While it’s too early to draw any solid conclusions, there
appears to be a circumstantial link between the, until now unknown
MCAS and the angle of attack error messages reported early on
following the Lion Air accident. The FAA last week issued
an emergency airworthiness directive
 against the 737 Max 8
that said, “erroneously high single angle of attack (AOA) sensor
input could result in ‘repeated nose-down trim commands of the
horizontal stabilizer,’ which could be from the MCAS,”
according to the Aviation
Safety Network

Operators of the 737 Max aircraft wasted no time making clear
their feelings about Boeing’s apparent oversight in the release
of MCAS information. In a message yesterday, ASN says the Allied
Pilots Association (APA), which represents American Airlines Group
Inc. pilots, alerted its members … to the MCAS saying “it
applies nose down stabilizer in specific conditions when the
aircraft nears a stall,” the first time many pilots were made
aware of the system’s existence.

The APA said the logic behind MCAS was not mentioned in training
or in any other manuals or materials. Safety Committee Chairman
Capt. Michaelis stated, “It’s pretty asinine for them [Boeing]
to put a system on an airplane and not tell the pilots who are
operating the airplane, especially when it deals with flight
controls,” according to the ASN.

A Boeing message quoted by the APA said, “the MCAS
(Maneuvering Characteristics Augmentation System) is implemented on
the 737 MAX to enhance pitch characteristics with flaps UP and at
elevated angles of attack. The MCAS function commands nose down
stabilizer to enhance pitch characteristics during steep turns with
elevated load factors and during flaps up flight at airspeeds
approaching stall. MCAS is activated without pilot input and only
operates in manual, flaps up flight. The system is designed to
allow the flight crew to use column trim switch or stabilizer aisle
stand cutout switches to override MCAS input. The function is
commanded by the Flight Control computer using input data from
sensors and other airplane systems.

A January 2018 report of the new Boeing’s created
by the Brazilian ANAC
 briefly mentions the MCAS, but offers no
specific guidelines on its operation. Whether the Lion Air 610 crew
had any knowledge of the MCAS’s existence prior to their October
29 takeoff is unknown. Sources said Boeing risk assessment team
felt the chances of the MCAS going off in flight were so remote,
they felt an explanation of the system was unnecessary

Boeing told Flying through a prepared statement in part, “We
are taking every measure to fully understand all aspects of this
incident, working closely with the investigating team and all
regulatory authorities involved … Safety remains our top priority
and is a core value for everyone at Boeing. While we can’t
discuss specifics of an on-going investigation, we have provided
two updates for our operators around the world that re-emphasize
existing procedures for these situations.”

Capt. John Weaks, president of Southwest Airlines Pilots Union
(SWAPA) quoted in the Wall Street Journal said, “We’re pissed
that Boeing didn’t tell the companies and the pilots didn’t get
notice obviously, as well. But what we need now is to make sure
there is nothing else Boeing has not told the companies or the

Reprinted by permission of Flying magazine

Rob Mark is also Publisher of

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Source: FS – Aviation
Could Knowledge of Undisclosed MCAS Have Saved Lion Air 610?

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