What condition denotes a "hung start" in an engine?

A hung start in an engine is characterized by a scenario where the normal increase in N1 (the speed of the engine's low-pressure compressor) is halted during the start sequence. Typically, during a successful engine start, you would expect to see a steady rise in N1 as the engine gets up to speed. However, in a hung start, this progression is interrupted, leading to a situation where the N1 remains at a low value, which indicates that the engine has not achieved sufficient rotational speed to continue the start process successfully.

In the context of the other options, while some might indicate problems during an engine start, they do not specifically describe the condition of a hung start. For example, an evident rise in ITT (Interstage Turbine Temperature) does not align with the definition of a hung start, as it typically indicates that the engine is producing some level of thrust or combustion heat. The interruption of fuel flow usually denotes a different issue, such as a fuel supply problem or a fault with the fuel system, rather than the specific scenario of a hung start. Lastly, excessive rise in Np (propeller speed) may suggest issues related to propeller operation rather than the engine start process itself.

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