What defect occurs when the hole is not perpendicular to the surface due to improper use of a drill guide?

An angled hole is characterized by its deviation from the expected perpendicularity to the surface it's drilled into. This defect typically arises when a drill guide is not properly aligned or utilized, causing the drill bit to enter the surface at an unintended angle.

Maintaining perpendicularity is crucial in aerospace applications, as it influences the integrity and fit of components, ensuring that they meet strict safety and engineering specifications. An angled hole can lead to issues such as misalignment of parts, inappropriate load distribution, and potential failure during service.

Other options, such as a rifled hole, which is characterized by spiral grooves, or a barreled hole, which narrows at some point, relate to different types of drill defects not specifically tied to the angle of the hole concerning the surface. Multiple depth holes describe variations in depth within the same hole but do not target the alignment aspect. Thus, the identification of an angled hole as the defect emphasizes the importance of proper drilling practices in aerospace assembly.