The fan disc is a critical part of a turbojet engine, securing the bypass fan blades and connecting them to the low-pressure compressor and turbine. It must support the blades and transfer rotation while withstanding foreign object impacts. Fan disc failure is a serious problem, so they are made from one-piece titanium alloy forgings.
A fan disc is the part of a turbojet engine that secures the bypass fan assembly and connects it to the low-pressure compressor and turbine via the low-pressure shaft. The fan disc is one of the critical parts of any turbofan engine and performs several vital functions. The most important of these is securing the primary or bypass fan blades. The disc also serves to connect the bypass fan to the low-pressure shaft which, in turn, is connected to the rest of the engine’s low-pressure components. All peripheral components of the fan, such as the nose cone or roulette, are also compatible with the fan disc.
Modern turbojet engines consist of two basic sections: low and high pressure. Both consist of compressor and turbine components. The low pressure section has an additional part that is possibly the most important part of all. This is the bypass fan, which is the large multi-blade fan so conspicuously visible when viewing a jet engine head-on. This fan is one of the most critical parts of the engine and a major contributor to the engine’s thrust capability.
As big and impressive as this fan is, its single most important component is quite small and rarely, if ever, seen. This is a rather modest looking hub in the center of the fan blade assembly. Known as the fan disc, this part of the bypass fan serves several vital functions in the overall operation of the engine.
The first is the critical task of supporting the massive fan blades. These blades are subjected to intense mechanical stress during operation; As the most exposed part of the engine, they are often subject to foreign object impact. These unforeseen stresses can be caused by ingestion of loose objects on the track, ice, or even bird strike. The disc must support the fan blades in such a way that they can absorb these impacts without breaking and destroying the motor.
The second important function of the fan disk is the transfer of rotation from the fan to the low pressure compressor and turbine. This is facilitated by a shaft that runs from the fan disc to the rear of the motor core. The low pressure compressor is mounted on this shaft just behind the fan and the low pressure turbine at the rear of the engine.
There are several other peripheral components mounted to the drive, including the spinner or nose cone. This is the tapered center piece of the fan that ensures streamlined airflow into the fan. All of these dependent items mean that a fan disc failure is one of the most serious engine problems pilots can encounter. For this reason, most fan discs are made from one-piece titanium alloy forgings that are specially profiled to distribute loads and stresses effectively.
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