Basics of Fluid Dynamics:

Let understand this basics of Fluid Dynamics with the real incident that happened, how 350 people lost by Industrial competition and how Fluid Dynamics Plays an important role in this incident. Get start to learn the Basics of Fluid Dynamics 

350 lives lost by industry competition:

 On October 29, 2018, a passenger plane that started from Jakarta, fell into the sea In this accident, more than 189 people died. Since then, within the next 5 months, that is March 10, 2019, another plane that started from Ethiopia met with an accident and more than 157 people passed away.

Though both these incidents happened at a different time and different location, it has one common thing. Which is, both planes were built by a company called Boeing. Model: Boeing 737 Max-8.

The reason for these two accidents and the death of these many people is mainly because of the industrial competition between the manufacturing companies. Let's see What is that? Why did this cause a technical issue and kill many people? That is what this post is about.


   In this world, the number of passengers and cargo aircraft is more than 25,000. The top two manufacturers of this product are Boeing and Airbus. Worldwide, the top two of the fast-selling and highly used aircraft is the Boeing 737 family and the Airbus A320 family.

Boeing 737 family has more than 10,000 flights and the A320 family has more than 9,000 flights. Here, who sells the number of flights is always a competition between these two companies. When one company releases a better flight model it affects the sales of another company.

Moving forward, in 2014 what Airbus did was they updated their A320 flight and launched a flight called A320 Neo. The major change in this flight is the Engine. While using this new engine, fuel consumption is saved by 15%. Also, as there were no other major modifications, pilots were able to operate this flight with minimum training. Because of this, airlines profited to a great extent. So the sale of this flight was immense.

Now Boeing is left out. To sustain itself in the market, they have to release a model better than the Neo flight. So what they did is, they remodelled their 737's Engine. The change that happened is, the size of the engine increased. While remodelling, Airbus also increased the size of their engine. For them, the distance between engine and ground, that is called Ground Clearance. Because that distance was sufficient, they could mount the engine in the same place. But, in Boeing 737, the Ground Clearance was less and hence they could mount it in the same place they slightly lifted the engine and mount it above. Then released this as 737 Max-8.

The sale of this flight was better than the sale of Neo flight. Because of the change in the 737 max-8 flight, what happened was the Centre of Gravity (CG) of the flight was slightly lifted. Hence, while taking off, compared to the previous model, in this model the nose was slightly lifted. Now, to know the problem of lifting the nose a little above we need to know what is AOA.

Basics of Fluid Dynamics:

  • In the wing of a flight, when we draw a line between the trailing edge and leading edge, it is called chord line. The wind touching the flight is called Relative wind.
  • The angle between the relative wind and the chord line is called AOA. That is the Angle of Attack.
  • As this angle of attack increases lift produced also increases. But, after reaching a certain angle, the lifts drop drastically This is called a Stall angle or Critical angle.

Now let's see what happens when the angle of attack reaches the critical angle.

 Wings will be designed in this shape, like an airfoil. It is because of this shape, that generates the lift of the flight. Normally, you can see, the air molecules moving along with the wing and gets deflected at the end. But then, when this angle reaches the Stall angle, air molecules get separated soon and forms irregular swirls like this.

 This is the reason for the abrupt drop in the lift generated by the wings causing a stall. This stall angle differs concerning each type of wing. Mostly lies between 12° to 20°. In flights, they make sure that this Angle of Attack doesn't reach the stall angle If that occurs, the chances of crashing are very high.

 This is why they install an AOA Sensor or Angle of Attack sensor. And they continuously measure the Angle of Attack. In the case of commercial flights, there will be two AOA sensors.

 Generally while taking off, a huge amount of lift is needed. So, this angle of attack very close to the stall angle. In Boeing 737 Max-8 flight because the engine is placed a little above, nose tilt is higher than normal conditions. Because of this, the Angle of Attack also increases and the chances of stalling are very high.

 To rectify this problem, a software called MCAS, Maneuver Characteristics Augmentation System was installed. What this software does is collects data from one of the two AOA sensors and when the Angle of Attack is higher pushes the Elevator of the flight slightly downwards and so the nose is brought down slightly. So to overcome this problem rather than changing the design of the plane, just the software was updated and the problem was rectified.

 After the approval of the FAA (Federal Aviation Administration), Boeing started to use this software in flights. But then, they neither informed about this update nor the pilots were trained properly. But the pilots during their course raised a complaint stating that the nose is going down frequently. During this time, on October 29, 2018, the same model of flight started from Jakarta. In this what the pilots did was, they tried to lift the flight using their control stick. But this MCAS System malfunctioned and brings the nose down. The pilots repeatedly tried to lift the flight and each time, the flight was going down. And finally, it falls and crashes.

 On further investigation of the problem, it is found that MCAS malfunctioned because it processed the wrong data from the AOA system and crashed Only after this crash, it was revealed that there is a software called MCAS. Further details on how to switch off this MCAS was also updated in the handbook. What happened this time was, pilots weren't trained properly about this MCAS System. They were provided with just a one-hour iPad course. No simulation training was given.

 So this lack of training caused another flight accident in less than 5 months and killed more than 157 people. The first flight crashed at least 12 mins after take-off. But the second crashed 6 mins after the takeoff.

 In the second accident because the pilots were aware of this MCAS System they turned it off and also informed ATC about an emergency landing. Even then, unfortunately, this crash happened.

 After this crash, many countries banned the flying of the Boeing 737 Max-8 flight within their territory. (India also, on March 14, 2019, banned this flight).

 Only after such problems, Boeing was pressurized to update the software In the previous version, the MCAS system collects data from one of the AOA Sensors and processed it causing such accidents. In the updated version of the software, the MCAS system collects data from both the sensor, compares the same before processing While comparing, if the difference in the data is more than 5.5°, the MCAS system gets disabled automatically. And in this version, the pilot can override this system at any time.

 Even though these errors are rectified now, the competition between Boeing and Airbus and the carefree attitude of the FAA is the primary reason for the loss of more than 350 lives.

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