The saying that no news is good news is so true in aviation. The whole of 2017 passed without news of onboard fatalities in commercial aviation. Indeed there were no crashes of airliners on scheduled flights in the period between December 2016 and February 2018. This was the safest recorded period for commercial aviation. Then 2018 happened.

Deluge of accidents

They came in thick and fast: On February 11, 2018 an Antonov An-148 belonging to Saratov Airlines crashed minutes after taking off from Moscow killing all 71 people on board. A week later on February 18, an ATR 72-200 belonging to Iran Aseman Airlines crashed killing all 66 on board. On March 12, a Bombardier Q400 Flight 211belonging US-Bangla Airlines crashed in Nepal, killing 52 of the 71 people on board. On April 17 a Boeing 737-700 operated by Southwest Airlines as Flight 1380 suffered an uncontained engine failure resulting in one fatality. On May 18, a Boeing 737-200/Adv crashed shortly after take-off from Havana killing 112 of the 113 on board. On October 29 a Boeing 737 Max 8 Flight 610 operated by Lion Air crashed shortly after take-off in Indonesia killing all 189 on board.

2019 seems to continue from the record of 2018. Very worryingly, on March 10, 2019 a Boeing 737 Max 8 operated by Ethiopian Airlines as Flight ET 302 crashed shortly after take-off in Ethiopia killing all 157 on board. These last two cases, separated by less than five months, involved very new aircraft. The aircraft in the Ethiopian Airlines crash was only delivered on November 15, 2018. In the case of Lion Air Flight 610, the captain asked for the controller for permission to return to the airport due to flight control problems. Similarly, the pilot in Ethiopian case reported difficulties to air traffic control soon after take-off, and requested to turn back. The Lion Air crash is believed to have been caused by faulty sensor that suggested that the nose was tilted higher than it actually was. Several lawsuits have been filed by relatives of crash victims against Boeing. 

The Boeing 737 Max is the fourth generation of Boeing 737. The aircraft are powered by CFM International LEAP-1B engines. This new series was first placed into service by Malaysian Malindo Air (owned by Lion Air group) on May 22, 2017. 350 of the aircraft have been delivered as of January 2019. The 737 Max comes in four flavours: Max 7, Max 8 and Max 9 to replace 737-700, 737-800 and 737-900 respectively. The 737 Max 10 is supposed to compete neck to neck with the Airbus A321neo and fill the gap in the market left by the Boeing 757.

Taking no chances

The two accidents involving the Max 8 aircraft have still not been shown to be linked, and the similarities may well be a coincidence. Some operators are however not taking any chances. Several countries have grounded the 737 Max 8. This is reminiscent of the grounding of Comets following a series of accidents in 1954. China, Indonesia, Fiji, Singapore have all grounded the Boeing 737 Max 8. China flies 97, more than a quarter of the aircraft in operation. European Aviation Safety Agency (EASA) has suspended all Boeing 737 Max operations in Europe until further notice. Some airlines have also taken action: Ethiopian, AeroMexico, Aerolineas Argentinas, Comair and Cayman Airways have grounded their fleets of the aircraft. US regulator, FAA has however so far declined to take action, saying that there is no basis for grounding the aircraft.

Popular workhorse

The Boeing 737 is a short to medium haul narrow body airliner. It entered into service in 1967, being developed from the Boeing 727. It was initially a flop, but has grown to become the most successful and produced airliner with 10,478 units produced as of end of February 2019. It is closely followed by the A320 family. A longer version was designated 737-200, with the initial version becoming 737-100. Only 30 of the original 737-100 were produced. The Boeing 737 has become the favourite workhorse of Low Cost Carriers, LCCs.

The second generation was the Classic series, featuring the -300/-400/-500 series. These were produced from 1984. They were powered by CFM International CFM56 high bypass ratio turbofan engines. The 737-400 was a longer version of the 737-300, carrying upto 188 passengers. It was 3.05 m longer, and included tail bumper to prevent tail-scrapes during takeoff. The 737-500 was shorter, a direct replacement of the 737-200.

The third generation is the Boeing 737 Next Generation (737 NG, or 737 Next Gen). These are the -600/-700/-800/-900 series, and were produced from 1996. They feature a redesigned wing, greater fuel capacity and glass cockpit (i.e. digital flight instrument displays, typically as LCD screens as opposed to analogue gauges and dials). They are equipped with CFM56-7 engines. The most popular is the 737-800 variant, now to be replaced by the 737 Max 8.

Technological blunders

Technological faults after ‘improvements’ are not unheard of.  A series of crashes bedevilled the first commercial jet airliner, the British made de Havilland Comet in the early 1950’s. Three Comets were lost within a year of entering into service, resulting in their grounding. The fault was eventually traced to structural failure. These resulted in the improved and redesigned Comet 2, Comet 3 and later, Comet 4, but the company never recovered. The baton of commercial airliner design had been decisively passed across the Atlantic to US manufacturers who incorporated the results of the accident investigations into their designs of new commercial jet aircraft.

The technological improvements that are being investigated in the 737 Max 8 crashes are mainly software based. In developing the new aircraft, a larger engine had to be fitted under the wings of an aircraft design which was already low. The engines were moved slightly forward and higher up, in front of the Centre of Gravity, CoG. This however affected the handling of the aircraft in certain situations. The engine nacelles (covers) also produced lift at high angles of attack, further destabilising the aircraft. Boeing introduced a Manoeuvring Characteristics Augmentation System (MCAS) to address this. The system activates when the sensed angle of attack exceeds a threshold. The system may surprise pilots who are unfamiliar with its operation. Accident investigators will be interested in unravelling if MCAS or its sensors did indeed play a role in the crashes involving an aircraft design that has otherwise flown safely for several decades. If true, this will be a great problem for Boeing, especially having in mind the sneaky way in which MCAS was introduced for such a crucial phase of flight!

The reports that the first officer in the Ethiopian Airlines case had only 200 hours of flight are also disconcerting. This is very low.

The writer heads the Department of Flying Studies in the School of Aerospace Sciences of Moi University in Kenya. Views expressed here are his own. odido@aerospacekenya.com