What is a disadvantage of the axial compressor?

The choice indicating that axial compressors exhibit good efficiencies over only a narrow rotational speed range addresses a critical performance characteristic of these machines. Axial compressors are designed to operate optimally within a specific range of speeds, and as the rotational speed deviates from this range, their efficiency can drop significantly. This can lead to issues like surge or stall, which are undesirable operational conditions.

The narrow operational speed range requires careful design and control in applications, particularly in aircraft engines, which may undergo rapid changes in operating conditions. While axial compressors are known for their efficiency at these optimal operating points, their performance can be adversely affected outside of this range, making them less versatile than other compressor types in certain applications.

In contrast, the other options do not accurately reflect the inherent limitations of axial compressors. For example, while weight might be a consideration, it is not a primary disadvantage relative to their efficiency characteristics. Similarly, the manufacturing process of these compressors, while complex, is not a direct disadvantage affecting performance in the same manner as their operational efficiency across varying speeds. Lastly, claiming low heat tolerance does not directly address the unique performance profile of axial compressors, which can generally be designed to handle significant thermal loads.