8411.91 - Of turbojets or turbopropellers:

HTS subheading 8411.91 encompasses parts specifically designed for turbojets or turbopropellers. This includes a broad range of components that are integral to the operation of these types of gas turbines, such as blades, vanes, casings, and combustion chamber parts, when they are not parts of other types of gas turbines covered by the broader heading 8411. The key defining characteristic here is the intended application in jet engines or propeller-driving gas turbines.

This category is distinct from its sibling, 8411.99, which covers "Other" parts for gas turbines. While 8411.91 focuses exclusively on components for turbojets and turbopropellers, 8411.99 would include parts for turboshaft engines or other gas turbine applications not falling under the turbojet or turbopropeller classification. Therefore, the specific type of gas turbine the part is designed for is the primary differentiator.

Within subheading 8411.91, further distinctions are made to classify specific types of parts. Subcategory 8411.91.10 pertains to cast-iron parts that have undergone minimal processing, primarily limited to cleaning and basic machining for removal of casting imperfections or to facilitate subsequent manufacturing steps. The more comprehensive subcategory, 8411.91.90, covers all other parts for turbojets and turbopropellers that do not meet the specific criteria of 8411.91.10, encompassing a wider array of finished and machined components.