Boeing 737 MAX crisis: Ethiopian Airlines Crash (Part II)

This article was originally published on AeroTime News on July 26, 2019. 

If you have missed the first part of the timeline, check it out here:

It seemed like things have calmed down under the skies in Renton, as orders and deliveries continued as usual. Boeing’s commercial aircraft division saw an increase in deliveries and revenues in Q4 of 2018, compared to Q4 of 2017. Airlines were still keen to order the 737 MAX – from November 2018 until March 2019 carriers placed orders for 248 the aircraft.

Boeing even achieved its first 737 MAX delivery from the Completion and Delivery Center in Zhoushan, China, “marking a new era in Boeing’s partnership with the Chinese aviation industry”.

However, that was just the calm before the storm – a storm that pours to this day.

Ethiopian Airlines Flight ET302 Crashes

On 8:38 AM local time, an Ethiopian Airlines Boeing 737 MAX took off for a regularly scheduled flight between Addis Ababa, Ethiopia (ADD) to Nairobi, Kenya (NBO). The flight was to last an hour and a half.

Six minutes later, at 08:44 AM, Air Traffic Control lost contact with ET302. The last known location of the aircraft was recorded near Bishoftu, around 60 kilometers from Addis Ababa. 

Three hours after the airliner crashed, Ethiopian Airlines revealed that none of the 157 people onboard have survived the accident. 

The following day Ethiopian Airlines t grounded all of its Boeing 737 MAX aircraft. On the same day, the Civil Aviation Authority of China ordered airlines to park their Boeing 737 MAX family jets on the ground. Indonesia’s Ministry of Transportation followed suit and Lion Air together with Garuda Indonesia grounded the troubled aircraft.

However, the FAA had a different opinion – on the same day that Ethiopian Airlines, CAAC and Indonesian MOT grounded the MAX, the U.S. authority issued a Continued Airworthiness Notification. While other authorities foresaw the similarities between the two accidents, the FAA was shy to make a decision: “[…]this investigation has just begun and to date we have not been provided data to draw any conclusions or take any actions”.

Eventually, the FAA caved in on March 13, 2019. The American authority ordered every American airline to stop operating the MAX and prohibited the 737 MAX from entering the U.S. airspace on commercial flights. The U.S. was one of the last countries to ground the Renton-built airliner.

But a question still lingers: if Boeing issued an Operations Manual Bulletin (OMB) how to counteract the automatic nose-down movements, why did the Ethiopian Airlines Boeing 737 MAX crash?

Baby Boeing

If you could point out the maintenance on the Lion Air MAX as an issue, Ethiopian’s maintenance history was squeaky clean.

Except it encountered four flight control problems back in December 2018. Erratic altitude, vertical speed, uncommanded rolling to the right occurred during four different occasions in the span of seven days.

The issues did not reoccur.

But between the time that ET302 crashed and the Ethiopian Aircraft Accident Investigation Bureau (AIB) released the preliminary report, Ethiopian Airlines had to deny too many accusations regarding its standard of operations.

Firstly, the public questioned the total flight time of the First Officer onboard the flight, which equates to a total of 350 hours. However, Ethiopian Airlines rebuffed the claims that the First Officer did not have enough hours:


Secondly, the pilot training, specifically pilot type conversion from the NG to MAX, was also put on the stage. Yet again, Ethiopian Airlines had to deny the allegations about the quality of their pilot training:

At this point, the fingers stopped pointing at Ethiopian Airlines. Slowly, the still-positive public opinion of Boeing eroded into dust.

On March 17, 2019, The Seattle Times published an article that showcased how the FAA and Boeing certified the 737 MAX. The article stated that the upper management of FAA urged safety engineers of the authority to be quicker with their assessments to approve the plane. In addition, FAA tried to transfer as much as was possible of the certification process to Boeing.

The article not only exposed an alleged conflict of interest,  prohibited by Title 18 of the United States Code 208, but also pointed out negligence by Boeing.

For instance, documents that the manufacturer provided to the FAA regarding MCAS, the system could move the horizontal tail by a maximum of 0.6 degrees. Boeing’s Multi Operator Message to 737 NG/MAX customers, issued after Lion Air crash, states that “Stabilizer incremental commands are limited to 2.5 degrees” ‒ a number much higher than the FAA certified, the article claims. In addition, the system only read data from one AOA sensor. If it failed, MCAS will move the nose down, even if the plane is not in danger to stall.

But how did the 737, called Baby Boeing in the ’60s, grow up to become such a troublemaker?

Inherit design issues

Back in 1968, Lufthansa (LHAB) (LHA) operated the first commercial of the Boeing 737. There is no denying that the 737 is the best-selling jet. To illustrate, Boeing delivered the 10 000th 737 to Southwest Airlines (LUV) back in March 2018. Just two years ago, in 2016, Airbus celebrated their 10 000th delivery, when the European manufacturer shipped an A350 to Singapore Airlines (SIA1) (SINGY) .

Since the first baby Boeing entered service, the manufacturer has stretched the 737 numerous times. The 737-100 could carry a maximum of 124 passengers and was 29 meters (94 feet) long. The 737 MAX-10, the largest MAX family aircraft, can seat 230 people and is 43.8 meters (143.8 feet) long.

Another huge difference with MAX is the engines. In order to maximize the efficiency, Boeing had to put bigger engines on the newest member of the 737 family. As a result, the CFM LEAP-1B engines produced an unwanted aerodynamic effect – the MAX has a tendency to pitch up or simply put, lift its nose higher than intended. So, MCAS was the solution, which turned into a problem after the Lion Air Flight 610 crash. 

If the pilots were aware of MCAS and its intricacies, how come they could not save the doomed ET302 flight?

It all comes back to the fact that the Boeing 737 is a 50-year-old, over-stretched frame. As the Ethiopian Airlines Boeing 737 MAX made four uncommanded aircraft nose-down movements, the pilots were simply unable to recover the plane to normal flight conditions, even if they used procedures highlighted in the OMB.

The problem was the airspeed, at which MCAS activated. At 8:43 AM, a minute before the aircraft crashed, the left Indicated Airspeed showcased approximately 458 knots, while the right one indicated 500 knots. Due to the huge forces applied to the horizontal stabilizer by the air, the pilots were not able to move the horizontal stabilizer back to a normal position. Thus, the pilots were not able to recover the flight.

Mentour Pilot, a Boeing 737 Captain, highlighted the issue:

Even at 300 knots, both pilots in the video struggled to control the aircraft. The speeds on the Ethiopian Airlines 737 were much higher and with the last recorded altitude being 5 419 feet (1 651 meters) on the left and 8 399 feet (2560 meters) on the right, the Ethiopian pilots simply had no altitude to work with to recover the aircraft.

Ethiopian Aircraft Accident Investigation Bureau preliminary report

On April 4, 2019, AIB released the preliminary report regarding the Ethiopian Airlines Flight ET302 crash. In close cooperation with NTSB, BEA, EASA, Boeing and Ethiopian Airlines, the Bureau has provided initial findings regarding the flight.

The report indicates that the 737 MAX was in an airworthy condition and the crew possessed the required qualifications to fly the plane. The takeoff procedures were normal, including both values of the AOA sensors.

However, shortly after takeoff, the similarities between two crashes in Ethiopia and Indonesia became clear:

·       AOA sensors started to disagree – the left sensor reached 74.5 degrees, while the right sensor indicated 15.3 degrees;

·       The stick shaker activated and was present throughout the flight;

·       The 737 MAX made uncommanded nose-down movements, adjusting the trim level.

Thus, the conclusion was clear – the software, designed to prevent the Boeing 737 MAX from stalling, was at fault.

Boeing did not want to claim responsibility for the crash. In a statement dated April 4, 2019, Dennis Muilenburg expressed that the “history of our industry shows most accidents are caused by a chain of events. This again is the case here, and we know we can break one of those chain links in these two accidents”.

In addition, the CEO of Boeing noted that the update to MCAS is “nearing completion and anticipate its certification and implementation on the 737 MAX fleet worldwide in the weeks ahead”.

Months ahead, Boeing is still yet to present a final version of the update on the FAA’s table.


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