The design altitude for the testbed is 10 feet at the current flight weight. Unfortunately off-the-shelf blades won’t get you there. The upside; we have dialed-in the necessary power and have set off designing blades that will.
We came close to quitting the project during the summer of ‘09 while trying to resolve control issues in ground effect. A repetitive grind of field-tests in heat and dirt; hastily fab’ed set-ups of aircraft spruce and gorilla glue; and correlating computer models - before trying again. (this video was taken in November of that year, as we were clearing the demons from our shop)
The end result: knowing what doesn’t work; a just awarded patent for what does, and a pretty fantastic ride.
Piasecki’s -59 series aircraft proved a promising configuration that was never brought to fruition.
By the early 1960’s evolved models attained speeds of 75 mph, had flown indoors, within trees and under bridges. “While the Airgeep would normally operate close to the ground, it was capable of flying to several thousand feet, proving to be stable in flight.” These vehicles demonstrated the viability of the tandem-duct platform.
Unfortunately, the aircraft possessed the complex aero-mechanics of a helicopter - repeated twice. They utilized the same controls as a helicopter, requiring the same skills to fly, with the difficulty compounded by the intent of low altitude flight. “…the Army decided that the “Flying Jeep concept [was] unsuitable for the modern battlefield”, and concentrated on the development of conventional helicopters.”
Control coupling occurs when a maneuver about one axis is joined by an unwanted rotation about another. An airplane with too much dihedral will roll when commanded to yaw. A helicopter will yaw when pulling collective.
"High-pilot workload" is the euphemism used to describe an aircraft whose control coupling is particularly onerous.
The control system on the test-bed minimizes coupling. A command to pitch nose-up does not induce roll or yaw. No bucking, no spinning. Not very challenging.