What would indicate a failure in the ignition system during engine start?

• A. Normal ITT rise
• B. Complete engine shutdown
• C. No rise in N1
• D. Normal sound from the engine

Answer: (C)

A failure in the ignition system during engine start can be indicated by a lack of rise in the N1 parameter. N1 refers to the speed of the low-pressure compressor in a turbofan engine and is crucial for indicating that the engine is beginning to reach operational speed and generate thrust.

If the ignition system is malfunctioning, the engine may not ignite properly or establish the necessary airflow and combustion processes needed for start-up. As a result, the N1 will not reach the expected rise. This is a critical sign for pilots and maintenance personnel, as it shows that the engine has not started and could suggest issues with the ignition system itself.

In contrast, a normal ITT rise would indicate that the engine is heating up as it begins the start process, which is expected when the ignition system is functioning correctly. A complete engine shutdown would not typically indicate a failure in the ignition system during the start phase, but rather suggest other operational issues. Similarly, a normal sound from the engine does not provide tangible evidence regarding the ignition's functionality; sounds can be misleading without correlating parameters like N1.