Optional warning light could have aided
Lion Air engineers before crash: experts
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[November 30, 2018]
By Jamie Freed and Eric M. Johnson
SINGAPORE/SEATTLE (Reuters) - An optional
warning light could have alerted engineers about mechanical faults on
Lion Air's Boeing 737 MAX jet that crashed last month, experts said,
sparking an industry debate over whether installing the system should
become mandatory.
Lion Air did not install the AOA DISAGREE alert, which warns pilots when
the "angle of attack" (AOA) readings do not match, because it is
optional and not required by regulators, Managing Director Daniel Putut
told Reuters.
The angle is a key flight parameter that must remain narrow enough to
preserve lift and avoid an aerodynamic stall.
A faulty AOA reading led the doomed Lion Air jet's computer to believe
it was stalled, prompting the plane's new anti-stall system, called the
Maneuvering Characteristics Augmentation System (MCAS), to repeatedly
push down the nose.
That made it harder for pilots to control the Boeing jet which crashed
on Oct. 29, killing all 189 people on board, Indonesian investigators
told parliament last week.
![](http://archives.lincolndailynews.com/2018/Nov/30/images/ads/current/lincolntheatre_sda_031016.png)
"In retrospect, clearly it would have been wise to include the warning
as standard equipment and fully inform and train operators on MCAS,"
said Clint Balog, a professor at Embry-Riddle Aeronautical University.
"I expect you will see this warning included in future MAX production
and retrofitted into already delivered MAX aircraft."
Boeing and the U.S. Federal Aviation Administration (FAA) made the AOA
alert an optional feature for the 737 MAX, meaning it was not deemed
critical for safe operation.
The FAA has said it will continue to participate in Indonesia's
investigation into the Lion Air crash and take further action if needed
based on findings from the probe.
Indonesia's civil aviation regulator said it would follow the FAA's lead
as to whether the AOA DISAGREE alert should be made mandatory for local
airlines.
(GRAPHIC: Lion Air crash investigation - https://tmsnrt.rs/2RiugFP)
DEBATE ON COCKPIT INFORMATION
There has been a long-running industry debate about how much information
should be displayed in the cockpit, notably about the angle at which the
wing is slicing through the air.
Several carriers, including American Airlines, Southwest Airlines,
Canada's WestJet, Singapore Airlines offshoot SilkAir and Dubai's
flydubai, said the AOA DISAGREE alert was installed on their 737 MAX
jets before the Lion Air crash.
Some airlines have also installed a separate optional gauge that gives
pilots a direct AOA reading in the cockpit.
American Airlines and SilkAir already have the gauge, while Southwest
said it decided after the Lion Air crash to install the gauge on future
737 MAX deliveries to provide "supplemental visual feedback for
identifying erroneous AOA data".
Air Canada said it would install the gauge "soon" but did not clarify
whether it had made the decision before or after the Lion Air crash.
Boeing declined to comment on customer selections.
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![](../images/113018pics/news_q19.jpg)
Wreckage recovered from Lion Air flight JT610, that crashed into the
sea, lies at Tanjung Priok port in Jakarta, Indonesia, October 29,
2018. REUTERS/Willy Kurniawan
![](../images/ads/current/fitzpatrick_lda_SPONSOR_2017.png)
FAULTY READINGS
The planemaker has come under fire in the wake of the Lion Air crash
for not outlining the automated system, MCAS, in the flight manual
for the 737 MAX.
The new anti-stall system had also automatically pushed down the
nose of the doomed Lion Air 737 MAX jet on its penultimate flight
from Denpasar to Jakarta on the evening before the crash.
The pilots had told engineers there had been a disagreement of
altitude and airspeed readings based on cockpit alerts, a
preliminary report released by Indonesian investigators shows.
There was, however, no mention of an AOA disagreement in their
write-up, according to the report, and the plane was dispatched on
its final flight the next morning from Jakarta.
It crashed into the Java Sea and investigators have yet to determine
the cause.
Having the AOA DISAGREE alert installed would "definitely" have
helped, "not in the least for discussion with the mechanic and entry
in the flight log as information for the mechanics", Leeham Co
analyst Bjorn Fehrm said.
"I think given the introduction of MCAS, Boeing should make AOA
DISAGREE a free and mandatory update," Fehrm added.
The alert was offered as an option on the 737 MAX's predecessor, the
737NG, and several carriers contacted by Reuters said they had
installed it on the older model too.
The alert light turns on when the AOA indications disagree by more
than 10 degrees for 10 continuous seconds, according to an American
Airlines 737 MAX flight manual obtained by Reuters.
The doomed Lion Air jet had a 20 degree disparity throughout its
last two flights, the Indonesian report shows.
![](http://archives.lincolndailynews.com/2018/Nov/30/images/ads/current/humanesociety_sda022411.png)
The AOA DISAGREE alert could have aided if it was reported after the
penultimate flight, professor Balog from Embry-Riddle said.
"Maintenance, if they knew about MCAS, would have known the
potential for trouble that warning light would indicate."
"The bigger question here is did Boeing realize the potential for
this scenario if MCAS received bad AOA data?"
Boeing is weighing whether to launch a software upgrade to MCAS in
six to eight weeks to help address the scenario faced by the Lion
Air crew, Reuters reported, citing two people briefed on the matter.
(Reporting by Jamie Freed in Singapore, Eric M. Johnson in Seattle
and Cindy Silviana in Jakarta; additional reporting by David
Shepardson in Washington, Tracy Rucinski in Chicago, Allison Lampert
in Montreal, Tim Hepher in Paris, Aditi Shah in New Delhi, Adam
Jourdan in Shanghai, Conor Humphries in Dublin, Marcelo Rochabrun in
Sao Paolo and Alexander Cornwell in Dubai; writing by Jamie Freed;
Editing by Himani Sarkar)
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