Project Dibbuk is a book appearing in Deus Ex. It describes the project that resulted in the creation of the SH-187 stealth helicopter. Certain copies of Project Dibbuk contain a short overiew of the project while some of them provide more detail on the specifications and operation of the helicopters.
There are multiple copies of the book found throughout the game. For example, it can be found in UNATCO HQ and the MJ12 lab on Liberty Island, and in the MJ12 Helibase in Hong Kong.
Transcript
PROJECT DIBBUK
Overview
Domination/5F Clearance ONLY
... the noted failure of previous attempts to create a low profile rotary aircraft involved the acquisition and retrofitting of available military hardware that had neither the range, ceiling, nor electromagnetic transparency to avoid numerous eyewitness accounts or unauthorized military interactions. In addition to exacerbating public misconceptions about governmental operations, such encounters also jeopardized several key missions. PROJECT DIBBUK was initiated to address this issue through the creation of a "stealth" aircraft that could be used as a platform for a number of mission objectives...
Domination/5F Clearance ONLY
.. the goal of PROJECT DIBBUK was to create a long range, variable mission-capable rotary aircraft, realized to its fullest extent in the SH-187 "stealth helicopter." The production model SH-187 features a revolutionary engine powered by HIGH-EFFICIENCY ETHANOL FUEL CELLS with a flight range of over 9000 miles depending upon atmospheric conditions, and an extension of the adaptive armor technology that renders it INVISIBLE across 97% of the non-visible electromagnetic spectrum. Ideally suited for surveillance, insertion, retrieval, and limited interdiction, the SH-187 will often spend much of its operational lifetime within hostile territory, and therefore is also equipped with REMOTE DISABLING and scrambling for its key flight systems. If necessary, the vehicle can also be scuttled remotely...