Penta comprises of steerable underwater drive unit with two forward-facing counter-rotating propellers
An open rotor engine generates most of the thrust from two counter-rotating propellers
instead of a ducted fan.
This UAV was Air Drone's first prototype and was completed while engaged in a 3 year CRADA, Cooperative Research and Development Agreement with the US NAVY at Point Mugu Naval Air base, California between 2001 and 2004, which ultimately culminated in a US patent for RAI's VTOL Flying Car using 16 counter-rotating propellers
within a ducted fan enclosure.
In spite of the fact that the motor drives the counter-rotating propellers
via a planetary reduction gear (for optimal low-speed operation) both the motor and the transmission are mechanically insulated from the frame by rubber mounts.
Hanging from two huge counter-rotating propellers
, the Pogo had no trouble rising vertically or transitioning to normal horizontal flight during its 1951-1955 flight testing program.