A 30% scale AH-64E has been modified into a compound helicopter by Boeing to explore the possibility of increasing its speed and range.
By Unknown author (U.S. Army Aviation Museum, Ft. Rucker, AL) [Public domain], via Wikimedia Commons
The company says the AH-64E Block 2 Compound has a downward vertical fin along with a thrusting propeller at its tail. The stub wings have been enlarged as well.