The main idea here is how FADEC manages fuel scheduling while keeping the engine within safe temperature and stability limits. FADEC continuously determines the needed fuel flow to achieve the commanded engine speed and power, using measurements of turbine inlet temperature (ITT) and other sensor data to keep the engine operating safely. It adjusts fuel so the engine reaches the desired performance without exceeding IT limits and while avoiding conditions like surge or lean blowout. This is the core function: precise fuel metering and protective control to maintain performance and reliability. The option about controlling the cooling system temperature isn’t the FADEC’s role. Cooling system management is handled by the engine’s thermal management and cooling subsystems, not by the FADEC’s fuel-control logic. Similarly, measuring oil pressure and adjusting lubrication, or storing flight data, are functions of other systems, not the FADEC’s primary responsibility.

Raising the compressor pressure ratio makes the air require more shaft work to reach the higher pressure. As the pressure ratio climbs, the temperature rise during compression grows, so the energy per unit mass you must supply (roughly Cp times that temperature rise) increases. In real machines, the actual work is higher than the ideal due to compressor efficiency, so the shaft power needed grows even more with higher PR. Although increasing the pressure ratio can improve cycle efficiency by enabling better expansion or other thermodynamic SAMPLEbenefits, those gains can be offset if the system can’t provide enough cooling after compression or enough fuel to keep the desired mass flow and temperatures in balance. In short, compressor work increases with pressure ratio, and that rise can erode potential efficiency gains if cooling or fuel supply can’t meet the demand.

The air between rows of rotating blades is diffused by the stationary vanes known as the stators. After air is accelerated and given a bit of swirl by a rotor row, the flow would be misaligned and energetic for the next stage. The stator vanes between those rows are shaped to redirect the flow into a more axial direction and to slow it down, converting kinetic energy into static pressure. This diffusion between stages prepares the air for the next rotor, maintaining efficient compression. Rotors add energy to the flow, while nozzles and diffusers play different roles, but the between-rows diffusion specifically comes from the stator vanes.

The main idea is that Pt7 is the stagnation (total) pressure at a specific location in the engine, labeled as station seven. In turbomachinery notation, P stands for pressure and the subscript t indicates total (as opposed to static) pressure, which includes the dynamic pressure due to flow velocity. The number seven merely points to the exact station along the flow path where this pressure is defined. So Pt7 is the total pressure at that station. This is distinct from total temperature (which would be Tt7) or static pressure (which would be P without the t), and it isn’t referring to the nozzle exit pressure.