Boeing Knew About 737 MAX Problems with Sensor and Warning Light Failure Before 2 Deadly Crashes

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Boeing didn’t disclose to airlines or federal regulators that a warning light wasn’t working until after one of two plane crashes.

Boeing reported Sunday May 5, 2019 in a press conference that the company discovered after airlines had been flying its 737 MAX aircraft for several months that a warning light integrated with MCAS (Maneuvering Characteristics Augmentation System) in the cockpit was not working as intended. The warning light is designed to activate if there’s a disagreement between the two sensors on either side of the plane’s nose that measure the jet’s angle of attack — the angle between the oncoming air flow and the airplane’s wing. The safety alert apparently only functioned if an extra option was purchased with the aircraft. Boeing said Sunday that its engineers discovered that the warning light wasn’t functioning, due to a software mistake, “in 2017, within several months after beginning 737 MAX deliveries” in May that year. Two aircraft disasters involving the Boeing 737 MAX occurred well after their awareness of the problem.

Dear Boeing:
“You and your team should forfeit your compensation and should resign forthwith.”

— Consumer-Safety Advocate Ralph Nader, whose great niece died in the second MAX 737 crash

The warning light is significant because it warns of a malfunction in one of the jet’s Angle of Attack (AOA) sensors. The alert worked only on planes flown by airlines that had bought a separate and optional AOA indicator added to the main flight display panel, according to The Seattle Times aerospace reporter Dominic Gates.

However, pilots say that Boeing also never mentioned that the MCAS anti-stall system even existed in a 56-minute Apple iPad course for pilots. Part of the selling points of the Boeing 737 MAX provided that existing Boeing 737 pilots required minimal training with the new Boeing 737 MAX. The MCAS anti-stall system that pilots weren’t initially told about, was needed because jet engines in the newer Boeing 737 were so big they had to be moved forward and upward on the wings. The new placement of the jet engines changed the Center of Gravity of the aircraft, which caused the aircraft’s angle of attack problem because the weight distribution forces the tail down and the nose up. The high nose-up position puts the aircraft at risk of a stall, which could cause the aircraft to drop out of the sky. MCAS was designed to automatically prevent a stall crash.

It is absolutely basic in aviation design that no critical system should depend on one thing failing.

— Dominic Gates

To counter the risk of stalling, Boeing, one might say, kludged something together. They designed an automated system known as MCAS (Maneuvering Characteristics Augmentation System) that would automatically force the nose down if the angle of attack was too high. The Boeing 737 MAX has two AOA sensors — one on each side of the aircraft near the cockpit. Either single flimsy AOA sensor on either side of the aircraft could activate the vital corrective system. Boeing didn’t use a two-sensor system because a two-sensor system would have required more expensive Level D flight simulator training for pilots for FAA certification.

MCAS involved a software system to adjust aircraft performance based on data from either single sensor. But what if data from the sensor was wrong?

On October 29, 2018, when the first aircraft crashed, Lion Flight #610 impacted the Indonesian coast after a nosedive, killing all 189 on board. Boeing claimed “pilot error” caused the crash. However, the pilot had to struggle with the MCAS that he didn’t even know about.

When American Airlines Captain Dennis Tajer, spokesman for the Allied Pilots Association (APA), asked why pilots weren’t informed about MCAS, Boeing said they didn’t want to inundate pilots with too much information.

On March 10, 2019, the second aircraft crashed, Ethiopian Airlines Flight 302 was also forced into a steep dive caused by faulty sensor data input to MCAS. The aircraft crashed near the town of Bishoftu, Ethiopia six minutes after takeoff, killing all 157 people onboard.

American Airlines purchased the extra indicator option for the flight deck. In a meeting on November 27, 2018, American Airlines Boeing 737 MAX pilots were told that the flight deck’s AOA “disagree light” would light up if the AOA sensors were inputting disparate data — even while the aircraft was on the ground before takeoff. A disagreement of the sensors on the ground would be a “no-go item,” the plane wouldn’t be allowed to take off.

Later, Tajer learned conflicting information about the disagree light. Supposedly the disagree light is inhibited from activating while the aircraft is on the ground.

“We are being told by Boeing that the AOA Disagree Alert … is inhibited until 400 feet above ground level. We are currently awaiting written confirmation of this AOA Disagree Alert limitation as it is not detailed in any 737 flight crew manual.”

— American Airlines Captain Dennis Tajer, spokesman for the Allied Pilots Association (APA)

Boeing has a serious credibility problem. The misleading series of disclosures also indicates that the United States government’s involvement in the process of the design and certification of commercial jets by the FAA is flawed.

60 Minutes Australia: Liz Hayes investigates the disaster of Boeing’s 737 MAX jetliner. Why two supposedly state-of-the-art and safe planes crashed killing 346 people; why pilots now fear flying the 737 MAX; and whether Boeing could have averted the catastrophes (43:03).


CARDINAL NEWS | Flying the Boeing 737 Max 8: An American Airlines Pilot’s View from Inside the Cockpit, Explains MCAS System Connected to 2 Crashes

CARDINAL NEWS | Boeing and Air Safety Experts Have Been Wary of the Angle of Attack Sensor As a Possible Cause of “Pitch Trim Runaway” Since At Least November 2018

CARDINAL NEWS | China, Ethiopia, Indonesia Ground Boeing 737 MAX 8 Jet Following Ethiopian Airlines Crash

CARDINAL NEWS | President Donald Trump in Agreement with FAA Orders Grounding of Boeing 737 MAX Aircraft



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See also …
The Seattle Times articles by Dominic Gates | Long before first 737 MAX crash, Boeing knew a key sensor warning light wasn’t working, but told no one | Boeing Mismanagers Forfeit Your Pay and Resign: An Open Letter to Boeing CEO Dennis Muilenburg | Greedy Boeing’s Avoidable Design and Software Time Bombs is an Amazon Associate website, which means that a small percentage of your purchases gets paid to at no extra cost to you. When you use the search boxes above, any Amazon banner ad, or any product associated with an Amazon banner on this website, you help pay expenses related to maintaining and creating new services and ideas for a resourceful website. See more info at