FAA Powerplant Written Practice Test

How are blade numbers arranged upon the initial construction of a 54 blade turbine rotor?

1. Next to each other

2. 180 degrees apart

3. In a stacked formation

4. Randomly assigned

The correct answer is: 180 degrees apart

The arrangement of blade numbers during the initial construction of a turbine rotor, particularly one with 54 blades, follows a specific pattern for balance and efficiency. In this case, having the blades positioned 180 degrees apart is crucial for maintaining uniform stress distribution and minimizing vibrations during operation. This systematic arrangement helps to ensure that the rotor operates smoothly and efficiently, reducing the likelihood of mechanical failure. By positioning the blades in this manner, any forces exerted on one blade are countered by an equally powerful force from the opposite side of the rotor. This is particularly important in turbine engines where the operational environment generates significant stresses and dynamic forces. Properly balancing the rotor contributes to better performance and longevity of the turbine system. The other patterns mentioned, such as clustering blades next to each other or stacking them, would increase the likelihood of imbalanced forces, leading to potential complications during operation. Randomly assigning blade numbers undermines the structural and aerodynamic principles designed into the rotor system.