What should be done if the APU makes abnormal sounds during operation?

If the APU makes abnormal sounds during operation, the appropriate response is to immediately shut down the APU and inspect it. This step is crucial because abnormal sounds can indicate potential mechanical issues, such as a failing component or irregular operating conditions. Continuing to operate the APU without addressing these sounds may lead to further damage, create safety hazards, or result in operational failures that could affect the mission.

Shutting it down promptly allows maintenance personnel to conduct a thorough inspection to identify the cause of the abnormal sounds and perform necessary repairs or adjustments. Prioritizing safety and equipment integrity through this immediate action is essential in aviation operations.