Final answer:
The question concerns a problem during an aircraft engine start sequence where there is no rise in EGT after advancing the start lever with N2 below 35%. The likely culprits could be a fuel delivery problem, malfunctioning igniters, or issues with the compressors or turbines, necessitating a thorough check by maintenance personnel.
Step-by-step explanation:
The question relates to a situation in aircraft engine start-up procedure where there is no rise in Exhaust Gas Temperature (EGT) 20 seconds after advancing the start lever, which occurs when the N2 (the rotational speed of the high-pressure compressor) is below 35%. This is indicative of a possible malfunction during an engine start sequence. During a normal start, the EGT should start to rise as the fuel-air mixture ignites and the engine begins to operate, providing an indication that combustion is occurring and the engine is starting.
The lack of increase in EGT can suggest several issues: there might be a fuel delivery problem, the igniters could be malfunctioning, or there could be an issue with the engine's compressors or turbines. Since the gas is not leaking and the cylinder size remains constant, it suggests that the physical integrity of the engine is maintained, and the issue is more likely related to the components involved in fuel delivery or ignition.
Diagnosing this problem would typically involve checking the fuel flow, the condition and operation of igniters, and ensuring that the engine's compressor and turbines are functioning correctly. Qualified aircraft maintenance personnel must address these issues to prevent engine damage or failure during operation.