The recent Ethiopian Airlines crash has once again put the Boeing MAX 8 aircraft in the spotlight. Just five months ago, another MAX 8 being operated by Lion Air crashed, taking the total toll to 346. Aviation is statistically the safest mode of transport, and two crashes within such a short period are alarming.
Following the crash, more than 40 countries have grounded the aircraft until further investigations are carried out and changes are made. India's DGCA has also grounded the aircraft and currently Spicejet and Jet Airways operate the plane. With more than 400 aircrafts on order from Indian carriers, the MAX 8 plays a pivotal role in boosting India's aviation market.
© Utkarsh Thakkar / @vimanspotter
Boeing's MAX series is the successor of 737 Next Generation family (737-700/800/900), and the company is relying on it to churn out profits. Even Boeing has been making aircraft for decades, and its expertise is often unmatched. So, the only question that arises is, how can a modern airliner be this unsafe?
The MAX series was Boeing's response to Airbus's A320 NEO family. NEO stands for New Engine Option and while the fuselage remains unchanged, the engines are completely revamped to offer better-operating efficiency. Regional airlines worldwide require planes that are cheaper to operate, especially when aviation fuel is extremely dynamic globally. To compete with the NEO, Boeing started the MAX series and offered up to 14 percent more efficient engines along with increased cabin comfort. But, this came with a small challenge.
The Ethiopian crash investigation will take months to conclude, but initial data suggest striking similarity between the two crashes. The preliminary report on Lion Air crash is out, and we'll be relying on it to understand MAX 8's major flaw.
The MAX 8 is powered by CFM's Leap 1B engines and they are significantly bigger than the previous CFM 56 engines (used in the 737 NG). Adding to this, the 737 was designed decades back and has an exceedingly low ground clearance when compared to the A320. To perfectly fit the new heavier and bigger engines, Boeing had to make minor changes in the design ranging from lengthening the landing gear to moving the engine slightly forward.
© Aviation International News
It was found that the bigger engine meant the plane handled certain situations differently and there was also a slight shift in the centre of gravity. The relocation and new engine design created an upward movement, nudging the plane's nose upwards. If the nose is lifted sharply, the plane will continue gaining altitude and could also stall mid-air. A stall is when an aeroplane cannot generate enough lift to continue flying.
To compensate this upward movement, Boeing added a new system called MCAS (Maneuvering Characteristics Augmentation System) that prevented the plane from raising its noise to extreme levels. The system would automatically adjust the horizontal stabilizer and bring down the nose. To make these adjustments, MCAS relies on data from the Angle of Attack sensors.
© Wikimedia (AoA sensor for reference)
These sensors are located on the nose of the aircraft and calculate the angle at which the plane is climbing or descending in comparison to the oncoming air. In the case of Lion Air, faulty sensors triggered the MCAS and automatically the system tried to bring the nose down. According to the flight data recorder, automated MCAS repeatedly pushed the plane's nose down following take-off.
The most surprising part of the MCAS though is Boeing hasn't mentioned the addition of this system during pilot training or manuals. This meant the pilot were unaware that a programmed system is trying to bring down the nose. Even if the pilots tried to takeover manual controls, MCAS cannot be simply stopped by moving the yoke. They need to manually trim the aircraft to gain control, but how will they know this procedure when the existence of MCAS is unknown to them?
The Lion Air pilot had more than 5,000 hours of experience and the Ethiopian pilot had more than 8,000 hours. Preliminary reports do not point towards any kind of crew error. Reports say pilots have in the past complained about a similar nose-down anomaly in FAA's database (US regulator) as well.
Following the Lion Air crash, Boeing issued a bulletin to airlines operating the 737 MAX 8 advising pilots how to override the MCAS system. This week, the plane maker also announced it's working on a long-term plan to rejig the system and update shall be applied in the coming months.
We'll have to wait for the Ethiopian crash report to clear the air whether it was the same MCAS issue that caused the incident, or are there any other flaws in the airliner.
Boeing has described the MAX series as its fastest-selling family of planes, with more than 5,000 orders placed to date from about 100 customers. The last time an aircraft suffered successive fatal incidents was the McDonnell Douglas DC-10 in the 70s.
With inputs from preliminary report of Indonesian National Transportation Safety Committee and FlightRadar24