An important question. Curiosity.
For some of us, the airplane is a dangerous vehicle that carries big dangers. For some of us, it is the only available (for now) vehicle that can take us where we just want to go to the fastest. For some of us it is a great pleasure and excitement. Whatever emotions we may have, safety is our common expectation.
How safe are the airplanes?
The answer of this question is directly related to the level of our trust to science. Science is based on the same rules that give the same results for the same applications. We use the simplest condition of science when cooking. Think of a favorite dish (McDonalds with Coca Cola) or a prepared food (chocolate or pizza). Every time we eat a different piece of product we get the same flavor.
How is this possible?
Mixing the same ingredients under the same conditions and baking in the same way. If the quality of each item we use is the same, we always get the same flavor without exception. We cannot feel a difference between a Coca Cola produced in Europe and a Coca Cola produced in America. If we ever feel, then an ingredient or a process is used differently. The results are so obvious.
Science on planes is no different. Airplanes repeatedly tested under certain conditions give the same results. Engineers think and calculate the most difficult conditions that can happen. They test the relevant part of the aircraft against these most difficult conditions.
For example, the wings of an aircraft may carry 50% more load than the aircraft could be the heaviest. It is a value that the airplane cannot reach practically.
Another measure is spares. Critical systems have backups. If one fails, the other enters the circuit. Some systems even have a third spare. There are even systems where a fourth solution is available. They are all for safe landing of the plane.
Another measure is limitations. This means that additional measures are taken if a system or part is defective. If a tire of your car has burst, you cannot continue driving fast. You will head to the first service point and will be driving slowly. On airplanes, there are additional measures taken for certain failures in the same way. If a system is faulty, it is completely disabled. Some systems require backups to run independently. In some critical system failures, the aircraft is not allowed to fly until the system is completely repaired. Under icing conditions, it is washed with special chemical hot water. For this reason, sometimes unwanted delays occur prior to departure.
Another measure is regular maintenance. Airplanes are subjected to detailed checks at regular intervals. Some parts are tested, some are changed, and some are strengthened. The results of these worldwide treatments are collected and evaluated repeatedly. Some measures are tightened, some of the content is changed. Sometimes new measures are taken.
No work is independent from people, so the teams receive continuous refresher training. Special licenses and authorizations determine who can do what. Critical operations go through independent control of a second person. Every work done is written, approved and archived.
Passengers, luggage and cargo onboard the aircraft are checked against the possibility of dangerous (or hazardous) goods.
All these operations are carried out at regular intervals by regular surveillance of aviation authorities. It is checked at regular intervals. Improvement and development always continues. Whether or not there is a risk, accident, or loss, it is always tried to be done better. The improvements come back to us as increased security, cheaper and widespread service.
How do accidents still occur despite of all these precautions?
It is difficult to collect in a certain title. Aerospace is an experiential area that is learned by experiments & living. So much so that, although all sorts of possibilities are predicted, the conditions that have never been experienced before can come to fruition. These conditions may be due to weather conditions, maintenance conditions, materials, pilotage, air traffic, ground traffic, foreign material damage etc. Large or small, whatever type of accident is experienced, it is immediately investigated. The details are reported, and it is questioned whether there is a general problem that will affect other planes. If there is such a risk, immediate fleet-wise action is taken. The necessary lessons are taken from the unwanted situations to minimize the risks in the future. The Federal Aviation Administration (FAA) has a website devoted to this subject (but not recommended if this subject is bothering you); http://lessonslearned.faa.gov/
The value and convenience that civil aviation adds to our lives is so high that it cannot be compared with losses. Bad scenarios bother us, but air transport is still the least risky form of transportation with a probability of 16 million 1. Airplanes are an indispensable part of our lives. It is constantly being tried to provide safer conditions with better and more advanced models, teams, equipment and applications.