It will be quite difficult to find at least one detail on the plane that was made “just like that”. Each element of the large iron bird has a constructive purpose. Including the propeller shown in the photo. It is difficult to believe that he is able to somehow affect the aircraft's ability to fly. So, it's time to figure out what it really is for.
As you might have already guessed, the small propeller sticking out of the plane's fuselage is not at all a piece of Carlson's wardrobe, who lives on the roof. This device is called a "ram air turbine" or simply RAT and is a backup electric generator and hydraulic pump. It is necessary in the RAT aircraft so that in an emergency situation the machine does not lose power, and also retains the ability to maintain the pressure in the hydraulic booster control system.
The emergency turbine is released automatically as soon as the main and backup power supplies fail. RAT is also issued in the event that the aircraft has problems with the hydraulic system (or there is a complete failure). The aircraft also has a mechanism for manually forced release of the RAT. It is noteworthy that initially the emergency turbine was installed only on military aircraft, but today it is also installed on civilian aircraft.
The principle of operation of an aviation emergency turbine is very simple. In fact, this is an ordinary wind generator, a source of "clean" energy, which works by untwisting the moving elements with air currents. The electricity produced by the RAT is quite enough to prevent the aircraft from crashing if the above-mentioned components and assemblies fail.
As a rule, the dimensions of the RAT propeller are in the range of 80-90 cm. On military vehicles, they are even smaller. The power of the generator, depending on the aircraft model, varies from 5 to 70 kW. The largest emergency turbine in our time is on the Airbus A380 aircraft - the dimensions of the propeller are 1.63 meters. Some Soviet aircraft did not have an emergency turbine, as an automatic rotation system was used instead, which performs the same functions.
If you want to know even more interesting things, you should read about why IL-96 is not used for passenger transportationeven if the president flies on it.