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The Probable Cause of the Lions Air and Ethiopian Air Crashes

Mike has a keen interest in aviation safety as his son is a 747-400 Captain for Atlas Air Cargo.



Disclaimer and Sources

This article is based on information from the following sources:

  • Wikipedia
  • The Seattle Times
  • Washington Post
  • The Air Current
  • A conversation I had with my son, who is a seasoned captain for Atlas Air Cargo and flies 747-400s to destinations around the world

This article is published prior to the FAA, NTSB, DOT, and FBI investigations having been completed. Every effort will be made to update this article to the latest information once those agencies have completed their investigations.

Factors That May Have Caused the Crashes

After doing my research and analysis, I have come to the conclusion that the following factors were at work to cause the Lion Airlines and Ethiopian Airlines to crash shortly after take-off:

  • The variations of the 737 airliner.
  • The FAA giving Boeing permission to approve and certify the airworthiness of their own design modifications.
  • The failure of the MCAS system.
  • The airline industry's lack of sufficient training for pilots, because time is money.

The Variations of the 737 Airliner

In the late 1960s, the Boeing 737-100 was rolled out as a narrow-body airliner that was intended for use as a regional carrier and to be competitive with other narrow-body aircraft manufactures of that time. It was not built to be used as a long-haul passenger carrier. But as the years passed, it was modified to haul more passengers and add more power, so it became the workhorse of many airliners around the world. The following are the model numbers of each of the variants:

737-100, 200, 300, 400, 500, 600, 700, 800, 900, MAX -8, 9, 10.

As one can see, there have been many variations of the same basic aircraft design. The 737-100 fuselage length is 94 feet; the fuselage length of the MAX 10 is 143.7 feet. That is a difference of almost 50 feet. Of course, with all that increase in length, it means that more passengers could be accommodated as well. The -100 has a maximum passenger capacity of 85, while the MAX -10 has a maximum capacity of 188 passengers.

More powerful engines were also added as it was modified to handle the longer fuselage and passenger weight. The MAX series has much bigger engines than the other variants, so they mounted the bigger engines forward from where the early variants were mounted and increased the landing gear strut height as well.

The Maneuvering Characteristics Augmentation System (MCAS)

Boeing was concerned the additional weight and bigger engines, changes the center of gravity of the airplane and under certain conditions it could stall. So, they designed what they thought would be a fail system that would take over at the instant the airplane started to stall and automatically push the nose down by moving the horizontal elevator down, causing the tail to pitch up and the nose to move down. The system is designed to operate without the crew knowing that it is activated and to behave with the same flight characteristics as the 737-800 that they are familiar with.

How the MCAS system should work.

How the MCAS system should work.

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MCAS Theory

The MCAS works on the input from two tiny wing like devices called Angle of Attack Sensors (AOS) mounted on both sides of the nose of the airplane.

Figure 1 shows If the airplane is sitting on the ground both of those sensors are supposed to be aligned with the wing and provide zero input to the MACS.

Figure 2 shows the airplane is in flight with the nose up, the sensor is supposed to indicate a positive angle of attack. If the angle of attack is too positive it will indicate a stall condition. (A stall is created when the nose of the airplane is so high that the wings have lost lift and the airplane has lost the ability to fly.)

Figure 3 shows the AOS sensor indicating a stall condition and the MCAS rotating the horizontal elevator to raise the tail and lower the nose of the airplane. If the AOS is sending faulty information to the MCAS, the system will go into a dive because it thinks the plane has stalled. I have found evidence that there is an override however, but it is very difficult to operate when the system fails as it will return control back to the MCAS every five seconds and cause a porpoising effect of the flight path.

The preliminary data from the flight data recorder of Lion Air indicates the AOS as being faulty. The AOS on the Ethiopian Air was supposed to have two AOS', but only one of them was providing input to the MCAS.

My son's experience during departure is the crew is very busy and that is when the MCAS takes over and tries to nose the plane down at a very high speed. The crew then has to figure out what when wrong at a low altitude and there is not enough time to recover from that steep high-speed, uncontrolled dive, thus resulting in disaster.

Lack of Training on MCAS

Because the MCAS system is integrated into the flight control systems and is autonomous, there is no pilot intervention required. Therefore, the reasoning is that only minimal pilot training is required to provide an overview of the system. Some airlines gave their pilots a one-hour overview on an iPad. Airlines like Southwest that uses the 737 series exclusively are always concerned about time and money for additional training, so they thought this was a great feature for the MAX series of 737s.

The Aftermath

The confluence of these factors at the same time may have caused the Lion Air and Ethiopian Air Disasters. This raises many questions:

  • Should the FAA allow aircraft manufactures to certify their own designs and modifications?
  • Should autonomous systems be integrated into aircraft without a means to override those systems?
  • Should more training be provided to crews who are responsible for the lives of their passengers and others?
  • Did Boeing try to hide the MCAS system from operators of the MAX series aircraft because they thought the operation would be foolproof?

The BP Oil Spill

The BP oil spill in the Gulf of Mexico was caused by the same lack of oversight and allowed the prime contractor to certify their own equipment and operations. It turns out the readings they reported were out of specification for safe operation of the rig and were the root cause of the blow-out of the rig. This is what happens when authorities who are responsible for the safety of others allow self-certification of equipment and processes.

Thanks for reading this article, and stay tuned as more information becomes available.

Update: March 22, 2019

Boeing has plans to modify the MCAS to receive inputs on both Angle of Attack Sensors and an indicator that will signal when the two sensor inputs are in disagreement. A digital display option will also be made available.

This content reflects the personal opinions of the author. It is accurate and true to the best of the author’s knowledge and should not be substituted for impartial fact or advice in legal, political, or personal matters.

© 2019 Mike Russo

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