What action should be taken after notifying Ground Control about an APU emergency?

Requesting fire department assistance after notifying Ground Control about an APU emergency is a crucial action because the APU can pose significant hazards, such as fire or toxic fumes, especially if there is a malfunction or failure. Involving emergency services ensures that trained personnel are on standby to manage any potential fire or safety issue, providing a rapid response if the situation escalates. It is vital to ensure the safety of the aircraft, crew, and passengers, and having fire department assistance prepared is an essential part of emergency protocols in aviation.

While preparing for an emergency landing is important, it typically follows the assessment of the situation and may depend on further instructions from Ground Control. Starting the APU again could exacerbate the situation if it caused the emergency, and turning off all electrical systems may not be appropriate without assessing the overall status of the aircraft and the specific emergency.