'Personal Air Vehicle' VTOL jump-copter in key flight test
Whirly, winged wonder-craft gets automated controls
A radical autogyro jump-copter "Personal Air Vehicle" able to make vertical takeoff and landings but cruise in winged flight like an aeroplane has achieved a key flight-test milestone.
The Personal Air Vehicle (or PAV) is a new design from Carter Aviation of Texas, which has been at work on its "slowed rotor/compound" (SR/C™) technology since 1994.
"This is an exciting time for us," enthused company prez Jay Carter Jr in a statement announcing the first flight. "Our first aircraft proved the viability of our technology. This aircraft translates that technology into a viable consumer product."
According to the statement, released last week, the new SR/C PAV design completed a 36-minute flight on 5 January. A 30+ minute flight is an important achievement for Carter, as it is one of eight "milestones" specified in an economic-development-incentive deal the firm has with the city government of Wichita Falls, Texas (where the company is based).
An SR/C aircraft has wings and a propellor like a normal light aircraft, but it also has free-spinning rotors like an autogyro. A regular autogyro can take off following a very short roll, but it can't lift off vertically: however the Carter PAV is expected to be able to.
It does this by using a small engine-driven "pre-rotator" assembly to gradually spin up its rotors to high speed while sitting stationary on the ground. The pre-rotator doesn't have to transmit much power so it has insignificant size and weight compared to a helicopter's transmission: and the engine isn't required to furnish the massive grunt necessary to support the aircraft in a hover, either.
The weighted rotor tips nonetheless mean that after a while there is a large amount of energy stored in the whirling rotor disc, rather as in the case of a spinning flywheel. To lift off, the pre-rotator is declutched and the rotors' pitch increased so that they bite air instead of spinning without resistance. The aircraft lifts off.
Left to itself, the craft would soon come down again as the rotor blades slowed, but meanwhile the propellor is pushing it forward to flying speed and the blades begin to turn on their own due to the forward motion: the craft is now flying like an autogyro. As speed increases still more, the rotors are slowed down to reduce drag (this is the Cartercraft's other main special sauce apart from the pre-rotator) and the wings take the strain. At full speed, the jumpcopter is flying as a normal wing-and-prop light aircraft.
Every landing is an autorotation !!!!
As an ex-military helicopter pilot who remembers doing many, many autorotational landings during training and on-going pilot tests the memory of them still gives me the sh!ts. Autorotational landings are a one shot deal - you get it right or you crash, there is no inbetween conclusion. The crash may simply damage the aircraft if you get it mildly wrong or kill you if you get it very wrong - I couldn't face that on every flight. I still remember the feeling in my stomach and the loosening of my bowels as the instructor rolled off the throttle or reached for the High Pressure fuel cock...
By coincidence an old friend developed recently a new bad habit and made last summer a pilote license for autogyros. One year later he is the proud owner of such a thingy and finally dragged me to the hangar to show off with his rickety thingy.
Well, so what?
Well, there were about four or five autogyros in the hangar (from at least three different manufactureres, one selfbuild (!)) and they ALL had either an electric starter motor on the rotor shaft or - even better - the more expensive models had a belt-drive system to temporarily divert power from the propeller shaft to the rotor. I asked for what this is used, as it was clearly not powerful enough to produce significant lift as it's done in a helicopter.
"Well" he said "that's for accelerating the main rotor a bit to shorten the take-off distance. They all have that."
Guess Carter lost exclusivity on that assessory of an autogyro about sixty years ago...
Rehash of an old idea
Unpowered rotating wings are not a new idea, in fact they predate the commercial development of the powered-rotor 'copter.
From what I understand -having examined a few autogyros at an aircraft maintainer's hangar some years back- they are easier to fly than a regular 'copter (no collective lever, and no rotor-induced yaw to complicate the control-inputs) but do have one or two nasty vices that powered rotors don't have.
The advantage over fixed-wing is that by running-up the rotor on the ground, a very short takeoff run is possible. Likewise on landing the lift from the rotor is maintained down to almost zero airspeed, making for a short roll. The things they can't do, of course, are to takeoff or land vertically, or hover.
As for me, I'd love a fullsize one of these to go to work in:
-A black one, naturally.
Now, that would turn heads. ;-)