The Pratt &amp; Whitney-Allison 578–DX geared propfan demonstrator engine, installed on an MD-80 testbed aircraft.
Ron Kawai
<a rel="nofollow" class="external autonumber" href="https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20080015836.pdf">[1]</a>; NASA/CR. 2008-215141. Figure 4. Ultra-high bypass ratio propulsors designed, built, and flight tested (page 3)