Final answer:
An Engineering Change Proposal (ECP) is a document used to propose changes to a project's requirements, explaining the reasoning and potential impacts on schedule and cost.
Step-by-step explanation:
The primary purpose of an Engineering Change Proposal (ECP) in the context of a program office like the Joint Airborne Paper Vehicle (JAPV) is to propose changes to the project's technical or operational requirements. An ECP is a document that outlines proposed alterations, the rationale behind these changes, the impacts on the current system, and includes detailed descriptions, justifications, and potential effects on cost and schedule. It is not designed to fund the project, design a new vehicle, or schedule project meetings, but rather to systematically suggest adjustments to an ongoing project and to ensure that all relevant stakeholders are on the same page regarding these changes.