Lion Air Down

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Don:  thanks for the reply, with reference reading. It’s interesting stuff.  I’m not familiar with the 737 at all, and I had somehow come to believe that there is at least 2 AOA sensor inputs to the MCAS.  The leaked logbook entries indicated that one AOA sensor was replaced prior to the fatal flight.

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My version - cleared a visual 33R YYZ, no guidance. Just a nice bright sunny day. Very young FO flying fresh from line indoc. About 10 miles back he says "so is this where I activate the approach?" Ca

I'll chime in here.  Yes.  Every single time.  Of course the temptation is strong.  But speculation is not a risk free exercise. The question we might want to ask is, why do we allow ourselves to foll

I have seen some horrible write ups in my time.  I once had a crew (probably more than once actually)  Tell me their autopilot was not working but when pressed for specifics were unable to elaborate. 

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I see that a correction to the emergency AD that was issued on November 07 was issued on December 11, 2018. I may have missed it but in a search I don't see a link to it on the thread so here it is:$FILE/2018-23-51_Correction.pdf

The AD includes operating procedures for a Runaway Stabilizer:

(h) AFM Revision: Operating Procedures
Within 3 days after the effective date of this AD, revise the Operating Procedures chapter of the applicable AFM to include the information in figure 2 to paragraph (h) of this AD


2019-02-10_182533_FAA Emergency AD-Correction to AFM.jpg

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to me if a dual system has a single point failure then there should be an annunciation and the system rendered inop.  Especially in this case where a single point failure can cause such an issue.  The plan would have been more controlable without the system than it was with apparently.


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For the purposes of sharing aviation safety information only:

Wall Street Journal

Boeing and Regulators Delay Jetliner Fixes Prompted by Lion Air Crash

Software update, initially expected in January, now likely pushed until April or later

A Lion Air Boeing 737-800 aircraft on Oct. 10, 2018. The Oct.  29 crash of Lion Air Fight 610 has raised fundamental questions about the limits and potential downsides of cockpit automation. Photo: adek berry/Agence France-Presse/Getty Images
Andy Pasztor and Andrew Tangel, WSJ
Updated Feb. 10, 2019 4:12 p.m. ET

Engineering and regulatory complications are expected to delay safety fixes covering hundreds of Boeing Co. BA 1.68% 737 MAX jets until at least April, according to industry and government officials familiar with the details.

Boeing is developing revised software for an automated flight-control feature that can forcefully push down the nose of MAX aircraft and was implicated in a high-profile Lion Air crash in Indonesia this past October. But the work has dragged on months longer than initially anticipated following the accident, these officials said.

In addition to engineering challenges, they said, another reason for the delay stems from differences of opinion among some federal and company safety experts over how extensive the changes should be.

Originally, software updates were expected to be fairly straightforward and slated to be announced in early January. But since then, there have been discussions about potentially adding enhanced pilot training and possibly mandatory cockpit alerts to the package, according to one person briefed on the details.

There also has been consideration of more-sweeping design changes that would prevent faulty signals from a single sensor from touching off the automated stall-prevention system, officials said. But at this point, they said, such options appear to be losing favor among regulators.

The 35-day partial government shutdown—during which consideration of the fixes was suspended—also created further delays.

Over the weekend, a Boeing spokesman said the company “continues to evaluate the need for software or other changes as we learn more from the ongoing investigation.” He declined to elaborate on specifics.

Since the accident, the Federal Aviation Administration has said it is considering taking action depending on the results of the investigation and reviewing certain issues related to its certification of 737 MAX aircraft.

The Oct. 29 crash of Lion Air Flight 610 roughly 11 minutes after takeoff from Jakarta, killing all 189 on board, has raised fundamental questions about the limits and potential downsides of cockpit automation. The tragedy has highlighted the hazards when automated flight-control features fail or misfire, and pilots aren’t able to respond properly.

Boeing has faced criticism from some airline officials, aviators and pilot union leaders for omitting details about the new stall-prevention system in the 737 MAX’s manuals or training requirements, which were approved by the FAA.

The Chicago-based plane maker has said the process to create its manuals and training for the 737 MAX was consistent with developing previous airplanes, and that it provided information needed to safely fly the airplane. Boeing has said the airplane is safe and noted it is in operation around the world.

Boeing favors a relatively simple solution that would primarily reduce the power and, under some circumstances, probably the repetitive nature of the flight-control system in question, called MCAS, according to these government and industry officials tracking the process. That appears to be the most likely outcome, they said, though no final decisions have been made. And the timing for an announcement remains fluid.

The FAA is poised to mandate changes to the 737 MAX once there is a company-government consensus about the overall package.

The stakes in the current debate go beyond skirmishes over arcane engineering judgments or Boeing’s design philosophy. The upshot, according to some industry officials and outside safety experts, could affect future suits filed by lawyers representing families of victims.

The accident probe will take months to complete, as investigators look at factors ranging from maintenance to operations to aircraft design.

The Indonesian-led investigation has tentatively concluded that sensor-calibration issues during maintenance touched off the fatal sequence of events, according to people familiar with the process. Investigators also have said the automated flight-control system was central to the crash, and they have publicly identified a number of pilot slip-ups that appear to have played an important part.

The stall-prevention system was designed just for the 737 MAX, a variant of Boeing’s workhorse single-aisle jet that Boeing made its debut in 2015. U.S. operators of the new plane include Southwest Airlines Co. , American Airlines Group Inc. and United Continental Holdings Inc.

Among measures the FAA has considered was whether to require all 737 MAX airplanes to be outfitted with indicators that alerts pilots when sensors that feed into the stall-prevention system disagree, the officials said. So-called angle of attack sensors essentially reflect the angle of the plane’s nose versus level flight. Cockpit alerts that show when such sensors disagree are currently optional on the fleet.

Preliminary data released by Indonesian investigators points to the MCAS feature misfiring when incorrect signals from a single angle-of-attack sensor prompted the system to repeatedly push down the plane’s nose.

In the Lion Air crash, investigators have indicated the pilots fought the MCAS system as it strongly and repeatedly pushed down the plane’s nose, but didn’t follow an existing procedure to deactivate it. Indonesian authorities have recovered, and more recently downloaded data from, Lion Air Flight 610’s cockpit-voice recorder. But they haven’t indicated what clues it may provide about the crew’s understanding of the system, and why shortly before the fatal dive the co-pilot apparently eased back on his nose-up commands.

On MAX 8 models, under certain conditions, pilots may be unable to pull the plane out of a dive unless they react quickly and proceed to the most relevant portion of their emergency checklist. Outside safety experts have questioned how the FAA gave the green light for such a design lacking redundant software or hardware safeguards. One malfunctioning sensor or a single stream of faulty signals—called a “single point failure” in engineering lingo—can lead to a catastrophic dive, if pilots react improperly.

As part of the overall Lion Air probe, the FAA has said its experts are reviewing that and other issues around how the aircraft was certified to fly passengers.

Write to Andy Pasztor at and Andrew Tangel at

Appeared in the February 11, 2019, print edition as 'Boeing, Regulators Delay Jetliner Fixes.'

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