What transient temperature range is allowed for ITT, and for how long?

The correct choice indicates that a transient temperature range of 821ºC to 870ºC is permissible for a duration of 20 seconds. This range reflects established guidelines for engine performance during short-term operational conditions, such as transient conditions that may occur during takeoff or brief deviations in normal operating environments. Transient temperatures are significant because they allow for temporary excursions beyond the normal operating limits without causing immediate damage to engine components, assuming they are managed within specified time frames.

The specified time limit of 20 seconds is also crucial, as it establishes a threshold during which the higher temperature can be tolerated without leading to excessive wear or thermal stress on engine materials. This balance between temperature and time is essential for maintaining engine integrity and safety while maximizing performance during critical flight phases.

Understanding this transient capability is vital for pilots and maintenance personnel to ensure they operate within safety margins and adhere to manufacturer specifications. Thus, option B aligns with the required operational limits for these transient temperature excursions, ensuring the engine runs efficiently and safely under occasionally stressed conditions.