What constitutes the standard empty weight of an aircraft?

The standard empty weight of an aircraft includes the airframe, engine, and all the operating equipment necessary for the aircraft to function, including hydraulic fluid and full oil. Additionally, it accounts for unusable fuel and any optional equipment that has been installed. This comprehensive definition is crucial for understanding an aircraft's weight and balance and is foundational for flight planning and safety.

Recognizing that the standard empty weight includes unusable fuel is important, as it distinguishes between fuel that can be consumed during flight and that which cannot be used. This detail plays a key role in weight calculations, affecting the aircraft's performance and how much payload can be safely carried. Thus, the inclusion of both the standard components and optional add-ons provides an accurate total weight, which is essential in ensuring compliance with various regulations and operational safety practices.