What is true about aircraft structural units made from sheet metal?

Aircraft structural units made from sheet metal are indeed repairable using approved methods. This is crucial for maintaining the integrity and safety of the aircraft. When sheet metal is damaged, specific repair techniques can be employed, such as patching or using specialized bonding agents, which are governed by industry standards and regulations. These repair methods are designed to restore the structural integrity while ensuring that the aircraft continues to meet safety requirements.

This option highlights that repairability is a key aspect of aircraft maintenance practices, allowing for cost-effective solutions to restore functionality without necessitating the complete replacement of the damaged components. In numerous cases, approved reparative techniques can extend the life of sheet metal structures significantly while adhering to safety standards.

In contrast, the other options imply limitations or conditions that do not accurately represent the capabilities of sheet metal repairs in aviation. For instance, stating that these structural units are typically not repairable or that they often require complete replacement overlooks the established practices and technologies in aircraft maintenance. Additionally, suggesting that they are only usable in non-critical areas does not recognize the widespread application of sheet metal in critical structures where appropriate repair techniques can be effectively applied.