Question

(APU limits) An underspeed condition exists when the tachometer reads below _____ RPM.

Option 1: 80%
Option 2: 85%
Option 3: 90%
Option 4: 95%

Answer 1

The underspeed condition threshold for an APU can vary and is usually indicated by operational guidelines specific to the APU model, like 95% or 90% RPM. It is essential to refer to these guidelines for an accurate value.

Step-by-step explanation:

An underspeed condition for an Auxiliary Power Unit (APU) is defined by specific operational limits set by the manufacturer. In the context of the question, it seems that the student is looking for a threshold RPM value below which the APU is considered to be in an underspeed condition. This would typically depend on the specific model of the APU and the guidelines provided by its manufacturer or the aircraft's maintenance manual. Since the question does not specify a type or model, it is not possible to provide a definitive answer without additional context. However, for educational purposes, one could say that an underspeed condition typically might exist when the tachometer reads below a certain percentage, such as 95%, 90%, or even lower. It is important to refer to the specific APU's operational guidelines or relevant technical documentation to determine the accurate percentage for an underspeed condition.