Sparkle, Sparkle Little Quad

I was inspired by Cirque du Soleil’s cool demonstration of quadcopter use in special effects where they outfitted some different quads with lampshades and then harassed a poor lamp technician. https://www.youtube.com/watch?v=7YqUocVcyrE

In the past six months I have built a few different 'costumes' for my second Phantom 2, named Sparkle. (Blog post on 11-20-14) First was a lampshade, then a few other LED dominated designs that are spectacular at night.

During the past few weeks I attempted to build my best imitation of a Star Wars battleship. With this project I have learned some things that I should have learned at the beginning of my quad adventure. VRS!  Yes, VRS; that state of air worthlessness that will suck your little investment down to earth like a V-22 Osprey hunting for bin Laden.

 

I began flying rotors with those cute little Syma $30 helicopters around the house. Slamming into walls, sucking up against ceilings and falling out of the air as I tried to descend even under full throttle.  I then advanced to quads, beginning with my Hubsan, just to continue my advanced skills into slamming, sucking, falling out of the air and blaming the manufacturer for releasing such a piece of rotor-poop. You’d think that I would have found an explanation to this calamity sooner than the day before yesterday.

If you have ever experienced the ‘flight characteristics’ described above, you have experienced Vortex Ring State (VRS). This sometimes tragic phenomena happens when descending straight down too fast and your rotor craft is flying right into its own prop wash.  A similar flight anomaly happens when you fly too close to your home ceiling or when you come very close to the ground. The natural blade turbulence that provides lift for your rotor blades is disrupted and your normal lift is upset.

Back to Sparkle and the Star Wars ‘costume’. In building the battleship modification, I used 3/8" EPO foam attached to DJI prop guards. (Prop guards are the basic building foundation for all of my Sparkle costumes as they are easily removed from the base P2 with eight little screws and I can change costumes.)

As you can see in the photo, I placed the rotors in ‘holes’ in the ship’s hull. (That was the first vortex disrupter.) I also decided to place a cool looking over head light structure. (2^nd disrupter) Then came Flight Test 1. Not good. Though Sparkle Wars did fly, it was very unstable. Why? I had disrupted enough of the required blade turbulence to place Sparkle on the edge of rotor stall.

My second modification was to make the overhead LED frame much thinner thus hoping to lessen the flow disruption. That worked better and Sparkle Warrior flew pretty well until a moderate gust of wind picked up and Sparkle began a Vortex Ring State stall that I simply could not power out of even though the terrific DJI stability logic tried to resolve the problem. In fact, adding power in a classic VRS stall makes things worse.

The best way to escape VRS, is to fly forward or sideways and get out of your own prop wash which is basically directly below your aircraft. Of course, you will need some air between your craft and Terra Firma. Or, you could 'just hands off hover'. Again, this happens quickly and many times the craft is starting to rotate making orientation very tough. Damn that gravity thing.

For me? One last Starship mod session with Sparkle before we move on to our next escapade.

In the meantime, mind your VRS, Grasshopper.

Final Note: Yesterday I removed the Star Wars costume from Sparkle as it simply was way too unstable. I never knew when it would veer off into a 'hard landing'. Apparently, that is why we never see rotor aircraft with rotors fit inside of 'holes'. It only works for fan ducted amphibious craft.