: The Defense Technical Information Center (DTIC) hosts a paper titled "The AH-64D Apache Longbow, Affordable Evolution," which covers system advancements.
: You can find R/C plans and technical blueprints for free at AeroFred . Apache Longbow Free Download
: The Internet Archive hosts free digital copies of the U.S. Army Apache Longbow flight manuals. : The Defense Technical Information Center (DTIC) hosts
If you are looking to "develop a paper" model, several free templates are available: Apache Longbow Free Download
: Sites like MyPaperCraft offer free downloadable PDF templates for building a paper model of the AH-64D.