What happens during a hung start in jet engines?

During a hung start in jet engines, the engine does initiate the starting sequence but fails to reach the required idle RPM, which is necessary for stable operation and continued combustion. This can occur due to several factors, such as insufficient fuel flow, compressor stall, or issues within the ignition system.

In this scenario, while the engine may run for a brief period, it doesn't achieve the minimum operational speed, which can lead to a situation where the pilot must take appropriate measures to ensure safety, such as aborting the start or shutting the engine down. This explanation encapsulates why the chosen answer accurately reflects the phenomenon of a hung start.

The other options depict scenarios that either do not align with the characteristics of a hung start or describe different starting issues. For instance, an engine starting normally without issues (the second option) denotes a successful start, which does not describe a hung start. Similarly, a complete failure to ignite (the third option) suggests that the engine did not start at all, and an immediate shutdown after start (the fourth option) implies a sudden rejection of the process, neither of which fits the definition of a hung start.