APUs approved under TSO C77b must fulfill the installation requirements of the aircraft type in which it is going to be installed. The following is a list of APU installation requirements:

• Part 21, Subpart O, Technical Standard Order Authorizations
• Part 23, Subpart E, for installation into Small Airplanes
• Part 25, Subpart E, for installation into Transport Category Airplanes
• Part 27, Subpart E, for installation into Normal Category Rotorcraft
• Part 29, Subpart E, for installation into Transport Category Rotorcraft