Turbine wheel burst occurs when ____________.

A turbine wheel burst occurs primarily due to excessive exhaust gas temperature (EGT). When the EGT exceeds the designed limits of the turbine components, it can lead to thermal stress and material degradation. The materials used in turbine wheels, typically nickel-based superalloys, have specific temperature thresholds. If these thresholds are surpassed, the metal can weaken, lose its structural integrity, and eventually lead to a catastrophic failure, such as a burst.

This scenario showcases how critical temperature management is within turbine engines. Proper monitoring and control of EGT are essential for maintaining engine health and ensuring safety. As EGT rises due to factors like incorrect fuel mixture, insufficient cooling, or operational extremes, the risk of turbine wheel burst increases significantly, highlighting the importance of ensuring EGT remains within the designed operational range.

In other scenarios, like high restriction in the exhaust system, while this can affect performance, it does not directly lead to a turbine wheel burst in the same way that excessive temperatures do. Similarly, debris entering the turbine can cause damage, but it is not a direct result of thermal stress, which is the leading cause in the context of the provided options. Engine overspeeds can indeed cause a variety of mechanical failures but are also not directly related to the