Which document must be adhered to when making modifications to an aircraft engine?

The Manufacturer's Maintenance Manual is the correct document to adhere to when making modifications to an aircraft engine because it contains specific guidelines, procedures, and instructions provided by the manufacturer regarding maintenance, repairs, and modifications of the engine. This document is essential for ensuring that any changes made to the engine meet safety standards and regulatory compliance, as the manufacturer’s guidelines reflect the intended design and integrity of the engine.

While other options may contain useful information, they do not specifically provide the authoritative maintenance procedures needed for engine modifications. The Engineering Specifications Document typically outlines the design parameters but may not include detailed maintenance or modification instructions. The Field Approval Process Document involves obtaining necessary approvals for modifications, but it does not guide the actual implementation of those modifications. The State Aviation Regulations Manual provides regulatory guidance, but it does not provide the specific operational details about the maintenance and modification of particular aircraft engines. Thus, following the manufacturer's maintenance manual is crucial for maintaining safety and compliance in aircraft operations.