The BIA is part of the system of objective control of the aircraft and other aircraft. He collects a variety of information, which, if necessary, can report on how the flight took place. Of course, data is encrypted and to understand them, you need to spend quite a complex job on their decryption.
A black box made of very durable material, inside it there are several insulating layers. All this is necessary so that data is not lost even after a heavy blow, because the BIA most of the benefit it provides for the analysis of air crashes.
In the "black box" is a lot of information, which relates to the operation of the aircraft. If you decrypt the data, it is possible to know the height above sea level for the duration of the flight, the actual height (i.e. the distance between the bottom of the aircraft and the tops of trees or roofs of houses), airspeed, heading, remaining fuel. And that's not all. Also in the "black box" is information relating to the operation of all mechanisms. For example, you can see lateral and horizontal g-force, angles of deflection of the rudder from neutral, the roll angle, the traverse stroke control, system voltage and so on. If the aircraft crashed, data from the BIA can talk about whether there was some failure mechanisms or accident occurred due to pilot error.
The engine, one of the most important parts of any aircraft will not remain without attention of the BIA. Are recorded not only basic, but even the secondary figures. For example, the number of revolutions, the position of the arms control, instantaneous fuel consumption and so on. Because of the large amount of recorded information pilots call the BIA "telltale", because he doesn't disregard practically nothing.
The cockpit is also very important, so in the "black box" and they are fixed. Because of the loud noise in the cockpit is not possible to record all the sounds. Is only that pronounced in a headset (headphones and microphone). In the near future the development and introduction of a new generation of BIA, who will record and video everything that happens in the cockpit.