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March 31, 2019

Accident Investigation (1/2)

Plane accidents are striking and very painful events. As the civil aviation safety rates are high, the issue takes even more attention.

The last two major accidents which involved Boeing 737 MAX occurred in the same aircraft type, age and flight phase (right after takeoff). The second accident occurred when the cause of the first accident was not fully explained. Both events have common aspects that cannot be ignored. This inevitably draws attention to the design criteria.

Today's planes can be considered as winged and wheeled computers. The higher the computer model, the more it can do for itself. This has two advantages; give the user freer time and fix the user's possible errors.

Let's give an example from our mobile phone. We're making settings that will extend the battery life in our “smart” phone. The phone automatically checks the battery level and turns off the screen if necessary. Or fade it. The whole purpose is to extend the battery life according to our settings and to provide us a longer operating time.

Well, let's just say we have an emergency. God forbid, there was a fire in the basement of the house. There's no way the people at home can hear or see us; The only option is to give notice by phone. We're on the phone to call the fire department. We unlock the key, but after 2 seconds, the display turns off again. We try again, it closes again. Before touching to the first digit, the phone again closes and locks the screen. The fire is progressing, the situation is getting serious. If the phone continues to give the same malfunction, it's not hard to guess consequences. If we imagine there are 150 more people in the same environment, whose life depend on this phone call, the situation becomes clearer.

A similar situation has occurred in both accidents, but the real reason is not yet clear.

If we continue with the phone analogy;

1. Did the person who was using the phone always enter the password incorrectly with panic?
2. Was the phone disconnected?
3. Was there any physical damage on the phone? (Did it fall or hit somewhere?)
4. Were the screen lock or battery life extension settings incorrect?

Each of these possibilities address very different fault sources.

The first possibility can be considered as the individual's own mistake. No matter how much or well a person is educated, the risk of mistakes can increase due to stress. Therefore, we can criticize why the password was there. However, the lack of a password also raises privacy and personal security problems. The phone can be captured, and all private information, documents, correspondence and pictures can change hand. It can cause great damage to the owner of the phone. If this person is in an important position in a large company, more people can be harmed. Should there be a password or not? We still use our passwords because second scenario pose a greater risk than the first. However, as in the example we provide, there is also another option which bypass the password in case of an emergency. This option was most likely made for the reasons mentioned here. Besides, was the person sober at the time of the incident? Was he healthy? Was it under the side effects of any drug? These will also be the questions that need to be evaluated.

2. Probability requires a little more scrutiny. Was the charge 100% full in the morning, but dropped to 10% before noon? Or the last charging was 2 days ago? These two situations lead us to completely different mistakes. The first is about battery life (design) and the second is about the user neglecting to charge. Or has a problematic program caused excessive battery consumption? This is a third sub-possibility. It is necessary to evaluate them all.

3. Probability requires even further examination than the second one. Because it is necessary to understand if the phone received a shock before the event. Or it was damaged due to the event? May be person dropped it just before the last call attempt. Or was it normal until the fire, but it fell spontaneously during the fire? Did something fall on it?

4. The possibility is that there is no physical damage to the phone itself but there is a problem in the program. In other words, the program consumes all of the battery life due to incorrect coding. The program was working correctly, but did the brightness consumed the maximum of the battery because of the malfunction of the sensor, which detects ambient light and increases the brightness of the display?

As we see, for a much simpler device than airplane, we can even question more probabilities on the table. Although the odds have fallen, there are other possibilities. None is excluded, because if the prospects do not give convincing explanations, the low probability scenarios will be examined.

No matter what caused the damage, and how severe it is, imagine there is a small recorder inside the phone keeping all the information. Analyses of all the parameters would be so helpful to reach a conclusion.

The evaluation of the aircraft is no different. Digital Flight Data Recorder and Cockpit Voice Recorder do this job in airplanes. They are also known as “black box”. Even when we consider the number of computers and systems in airplanes, we can see how broadly the investigation should be.

So, how is the real reason is defined among all the possibilities?

We will discuss this in the next article.