At the beginning of this week on Sunday 10th March 2019 the world woke up to the sad news of a plane crash by the Ethiopian Airlines which proved fatal with human lives lost put to 157 which was the total number of passengers on board. The passengers cuts across 35 different nationalities with Kenya being the worst hit nation with 32 of her citizens on board.
Image credits: Wikipedia CC-BY-SA-2.0 from Clemens Vasters]
The flight ET 302 a Boeing 737 MAX 8 aeroplane was en route from Addis Ababa Ethiopia to Nairobi, the capital of Kenya, a distance of 1,157KM with the flight time of approximately 1hour 38 minutes. But the plane which took off by 8:38 a.m lost contact six minutes after takeoff by 8:44 a.m and in about two hours later the Ethiopian prime minister offered condolence on the mishap via a twitter post by 10:48 a.m Ethiopia's time.
Apart from the high number of casualties, this may not have generated much controversy as this particular fatal crash had if not for two things: there was a similar crash involving a similar new Boeing 737 Max 8 five months ago in Indonesia.
Secondly, both aircraft crashed shortly after takeoff, and there was an issue involving altitude gain loss. The parallel was not lost to the world, and aviation industries in countries like New Zealand, and China have ground all 737 MAX 8 fleet citing safety concerns to be the reason for the action. These cancellations and drop of the particular model had led to billions of dollar loss in share revenue for the aviation giant.
A look at Boeing 737 MAX 8 Aircraft
The 737 MAX series are currently four which are made up of 737 MAX 7, 737 MAX 8, 737 MAX 9 and 737 MAX 10. The MAX is an upgrade of the popular Boeing 737 which took its maiden flight in 1967 and have sold more than 10,500 unit worldwide as of January of this year.
The MAX series is the fourth generation of the Boeing 737 with the program kicked off in the year 2011 and the first flight four years later in January of 2016 and as of 2019 has been an outstanding success with more than 5011 orders flooding in from different airline operators around the world.
There is a reason for this, the 737NG or 737 Next Generation planes which comprise of the third generation 737-600/700/800/900 series which was the design first launched in 1993 is not as powerful and fuel-efficient as the current fourth-generation 737-MAX series. Which means the 737 MAX 8 can travel for more extended range while saving on fuel and leaving less carbon dioxide emission, a decrease which is up to 20% when stacked against the older 737NG.
To achieve this, the 737 MAX makes use of the all-new CFM International LEAP-1B engine which offers more aerodynamic efficiency, also bigger and more powerful than the 737NG engines.
Image credits: Wikipedia CC-BY-2.0 from Clemens Vasters]
The nacelle, the aircraft engine cover, is bigger and more forward placed on the wing on the 737 MAX when compared with this image of the two aircraft put side by side- the 737MAX is the one on the right.
The aeroplane makes a three-dimensional movement when in flight which includes yaw, roll, and pitch. The placement of the nacelle this further forward results in a change in that stability of the aircraft's pitch (roll up or down movement).
With the powerful thrust of the Leap-1B jet engine, on the heavier Boeing 737, Max 8 plane tends to point its nose too sharply upwards which may lead to a stall while in manual flight. To avoid this, an emergency system that can correct the angle by pushing the nose down is automatically engaged to ensure lift is not lost.
MCAS the gift or the curse?
The system that ensures that lift is maintained is known as Maneuvering Characteristics Augmentation System or MCAS for short.
The larger nacelles, called for by the higher bypass LEAP-1B engines, changed this. When flying at normal angles of attack (3° at cruise and say 5° in a turn) the destabilising effect of the larger engines are not felt.
On flights with a normal angle of attack, say 3° at cruise and say 5° in a turn, the destabilising trait of the bigger nacelles necessitated by the high bypass Leap-1B jet engines are inconsequential. The sensors of the angle of attack have the job of informing the MCAS to redirect the nose of the plane downwards to forestall a stall from occurring.
The pilots of the ill-fated Lion Air Flight 610 that crashed in Indonesia last year struggled with MCAS as it continuously pointed the nose downwards until they lost the fight which lead to the crash that killed all 189 aboard.
The data from the so-called black box is consistent with the theory that investigators have been most focused on: that a computerized system Boeing installed on its latest generation of 737 to prevent the plane’s nose from getting too high and causing a stall instead forced the nose down because of incorrect information it was receiving from sensors on the fuselage.
“The pilots fought continuously until the end of the flight,” said Capt. Nurcahyo Utomo, the head of the air accident subcommittee of the Indonesian National Transportation Safety Committee, which is leading the investigation. The New York Times: In Indonesia Lion Air Crash, Black Box Data Reveal Pilots’ Struggle to Regain Control
After that disaster, Boeing issued a bulletin which reinforces their earlier statement that there is a manual override for the MCAS.
A day after this present crash, on March 11, 2019, Boeing once again posted a bulletin, this time around it is talking about an upgrade to the software of the MCAS. For details of this bulletin, please click here.
While there still on an ongoing investigation, no one can categorically state if the current air mishap has anything to do with the MCAS or even software-related, we await more information from the aviation disaster investigating teams who are working to unravel the cause of the fatal air crash.
My condolences to the family and friends that lost their dear ones in this great tragedy.
References
- Overview of the 737 Max 8
- Fuel Efficiency of 737 MAX vs 737 NG
- Technical Specification of MAX 8
- Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots
- Aircraft Principle Axes
- Leap Engine
- Boeing 737 Max 8 With Cfm Leap-1b Engines Receives FAA Certification
- Ethiopian Airlines crash: What is the MCAS system on the Boeing 737 Max 8?
- The New York Times: In Indonesia Lion Air Crash, Black Box Data Reveal Pilots’ Struggle to Regain Control
- Boeing Statement on 737 MAX Software Enhancement