Citation 550 Oral Practice Exam

The main idea is that certain surfaces and sensors must stay ice-free whenever the engine is running, to protect both performance and instrumentation. The bullet nose—the forward part of the intake—and the T1 probe (the total temperature sensor located in the inlet) are both heated continuously so ice cannot form on them. Ice on the bullet nose can disrupt airflow into the engine, and ice on the T1 probe can give false temperature readings that mislead engine control.

The engine inlet itself isn’t kept ice-free on a continuous basis in this configuration; its anti-ice is not required to stay on all the time, whereas the bullet nose and the T1 probe require constant heating during operation.