The arduous affair of air crash investigation commences in Ethiopia - a pursuit to find the cause of the crash of Ethiopian Airlines flight 320 departing Addis Ababa for Nairobi.
Long and tedious are the hours of combing through minuscule debris and piecing together wreckage like a jigsaw puzzle to recreate the accident. Months and probably years shall pass before a verdict of determination emerges from the Ethiopian Civil Aviation Authority.
At hand is a case of two new B737 MAX 8 aircraft crashing six months apart, and the public jury decries safety of the plane. What are the odds of a coincidence vis-à-vis manufacturer cause?
In the 50 years after the introduction of the wide-body jet airliners in the 1970s, a decline in aviation accidents (see chart below) occurred notwithstanding an annual 4.3 percent increase in aircraft production, according to IBIS World, a global market research company with headquarters in New York. This drop was largely a result of safety regulations and automation of flight control systems.
The International Air Transport Association (IATA) announced that the global accident rate (measured in hull losses per million flights of Western-built jet aircraft) was lowest in 2010 at 0.61 - that translates to one accident for every 1.6 million flights. Compared to 10 years prior, the accident rate dropped by 42 per cent. A hull loss is an accident in which the aircraft is destroyed or damaged beyond repair.
In May 22, 2010, Air India Express Flight 812, a Boeing 737-800 overshot the runway at Mangalore, India resulting in 158 deaths. The accident accounted for 65 per cent of casualties in 2010. It remained the deadliest accident involving the Boeing 737 Next Generation model until Lion Air Flight 610, a Boeing 737 MAX 8, the latest version of the 737 Next Generation model, crashed in 2018 with 189 deaths. Ethiopian Airways flight 320, also involving a MAX 8, joins the list of fatal accidents involving Boeing 737 Next Generation aircraft.
In the case of Air India Express, investigation attributed the accident to pilot error – the captain ignored warnings by the First Office to abort the landing. However, the peculiar similarities in the Indonesian and Ethiopian cases portends trouble for Boeing - both aircrafts were of the 737 MAX 8 model; both crashed just minutes after take-off; both struggled to gain altitude; and both appeared to ascend and descend several times before crashing.
It has been revealed that redesigning the 737 to produce the cost-effective 737 MAX 8 brought about considerable aerodynamic challenges, prompting the manufacturer to introduce a self-correcting mechanism. However, this wasn’t revealed in the original pilot training manual that accompanies every aircraft sold. And though Boeing eventually sent a secular to all airlines operating the MAX 8 with a recommendation for proper training of pilots on the new dynamics, two aircrafts crashing in such a short span has seriously damaged the reputation of the Boeing 737 MAX 8.
With several MAX 8 aircrafts grounded around the world, it does not help that by the time the Ethiopian Airlines plane went down Boeing was close to conducting a software upgrade that would eliminate the challenges relating to the model's self-correcting anti-stall mechanism.
The Boeing Company founded on July 15, 1916, by William Boeing is the largest global aircraft manufactures. The company had delivered 19,564 aircrafts, almost double that of Airbus (11,763), which came in five decades later.
There are about 21,450 commercial aircrafts in service worldwide, according to an Airbus global market forecast report, 2018-2037. The two leading aircraft manufacturers almost tie in current market share, each with more than 10,000 commercial aircrafts in service.
From 1974, fatal accidents involving a Boeing aircraft totalled 232, significantly outstripping other significant manufacturers – Embraer standing at 92 and Airbus, 30. However, the big difference can be attributed, partly, to the fact that the other two aircraft manufacturers were established much later – 1969 and 1970, respectively, when Boeing already had a number of older planes flying. Older aircraft are prone to accidents due to a phenomenon known as metal fatigue. Metal parts and surfaces of aircraft undergo weakening due to repeated forces and stress causing microscopic cracks and subsequent failure in parts. In new planes such as the Boeing 737 MAX 8, metal fatigue is ruled out as a probable cause of an accident leaving pilot error and manufacturing flaws as contending candidates.
The drop in aviation accidents in 2010 followed the same trend for the four primary aircraft manufactures (see the chart at the top of the page). Boeing had the highest decline resulting in almost the same number of crashes as Airbus in 2010. It is tempting to think the cause of the drop results from Boeing changing the safety procedure for their aircraft maintenance. However, another probable cause of the decline lies in passenger demand. IATA reported 2009 as having the worst drop in passenger demand since World War II. Passenger demand for the year was down 3.5 percent with an average load factor of 75.6 percent. Freight for the year had a decline of 10.1 percent with an average load factor of 49.1 percent.
In aviation, load factor refers to the capacity utilisation of an airline - it measures how efficiently an airline fills seats and generate fare revenue. In the preceding years, airlines had managed to raise their average passenger load factors by more than seven percentage points since 2001 thus using their assets more productively. The likely cause of the decline in passenger demand is the financial crisis of 2007-2008 that split over to 2009. The Dow Jones hit its lowest level on March 6, 2009, at 6,443 points thus wiping out disposable income available for recreational travel. There are less accidents when fewer planes are flying.
A rare occurrence
The decline in aviation accidents across the industry can be attributed to improved vigilance by aviation regulation authorities. The question in mind, therefore, is how much individual aircraft manufacturers like Boeing are investing in the safety of their planes. An answer to the query lies in the probability of two new aircrafts going down within a few months of service. The diagram below shows the same aircraft model accidents and service period.
From the chart above, since the late 1970s, there hasn't been an accident of the same aircraft model within two years of service - that's until the Boeing 737 Max 8. For the current generation, this is a rare event, thus the only plausible cause is a manufacturing fault. However, before 1970, the Boeing 727 had many accidents within a few months of service.
A majority of the crashes resulted from manufacturing defects. Hence, the probability of the same aircraft model crash happening within one year of service and resulting from a manufacturing defect is high - therefore, odds are stacked against Boeing on the Ethiopia Airlines crash.
The author is a data scientist.