What must all repairs or alterations be based on to ensure they're approved for return to service?

Repairs or alterations must be based on data that is GACA-approved to ensure they are compliant with the regulations and standards set forth by the General Authority of Civil Aviation. This requirement is critical because GACA approval signifies that the data has been vetted for safety, reliability, and thoroughness in meeting aviation standards.

Using approved data provides a higher level of assurance that the repairs or alterations will not adversely affect the aircraft's airworthiness or operational safety. It ensures that the procedures and processes followed align with accepted practices and regulatory guidelines, facilitating a safe return to service.

While manufacturer guidelines can also be crucial for specific repairs, relying solely on them may not encompass the broader regulatory requirements established by GACA. Thus, GACA-approved data represents the definitive benchmark for ensuring compliance in the repair or alteration process.