Ethiopian Boeing 737-8 Max crash: What is 'unstable vertical speed'

2019-03-11 07:47 - Selene Brophy
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The safety of the Boeing 737-8 Max has been called into question as Ethiopian has grounded its entire 8 Max fleet.

The airline has yet to determine the cause of the Ethiopian Airlines Boeing 737 passenger jet that crashed about 6 minutes after take-off, en route to Nairobi on Sunday - but has grounded the fleet as an extra safety precaution. None of the 149 passengers and eight crew members aboard survived the fatal incident. 

The Ethiopian Airlines incident is the second in less than six months with the new Boeing aircraft. A Lion Air Boeing 737 MAX 8 flight went down over the Java Sea in late October 2018, killing all 189 people on board. 

While investigations into the cause of the devastating crash is well underway, data by the Swedish-based flight tracking organization shared to Twitter states, the plane had "unstable vertical speed” 

“Data from Flightradar24 ADS-B network show that vertical speed was unstable after take off". 

Unstable vertical speed 

According to a local aviation expert who asked not to be named, as the crash is at a sensitive stage with official cause of the incident yet to be determined, "unstable vertical speed means the velocity at which the aircraft was ascending was erratic. Usually an aircraft’s velocity increases at a steady rate from when it commences its take off and climbs to its cruising flight level". 

State-owned Ethiopian is one of the biggest carriers on the continent by fleet size, with its last major crash was in January 2010, when a flight from Beirut went down shortly after take-off. 

Difficulties after take-off

The Standard reports Ethiopian Airlines CEO Tewolde GebreMariam says the pilot reported technical difficulties after take-off and asked for clearance to return to Addis Ababa. The pilot was given clearance to turn back, GebreMariam said, citing the air traffic controllers' record.

The pilot was a senior Ethiopian Airlines pilot who had flown more than 8,000 hours. He had an "excellent flying record," GebreMariam said.

A CNN report quotes Geoffrey Thomas, the editor in chief of Airline Ratings, as saying it had "no fluctuations and all of the sudden transmission ceased. That transmission ceasing indicates catastrophic failure in air."

The Chinese government has also since grounded all Boeing 737 MAX 8 jets, citing safety concerns, while Boeing has delayed plans to unveil its huge new 777X jetliner this week following the deadly crash of one of the company's aircraft in Ethiopia.

The aerospace giant said in a press statement that it was "deeply saddened to learn of the passing of the passengers and crew." It added that a "Boeing technical team is prepared to provide technical assistance at the request and under the direction of the US National Transportation Safety Board."

READ: Aviation safety by numbers: 3rd consecutive year of 'zero airline jet hull losses or fatalities in Africa'

The crash comes as a devastating blow to the African industry that was set on improving its safety record.  

In February, IATA's Airline Safety Performance report concluded that for a third consecutive year, airlines in Sub-Saharan Africa experienced zero jet hull losses and zero fatalities in jet operations.

"The all accident rate was 2.71, a significant improvement over the rate of 6.80 for the previous five years. Africa was the only region to see a decline in the all-accident rate compared to 2017. However, the region experienced 2 fatal turboprop accidents, neither of which involved a scheduled passenger flight." 

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