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. (2nd 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.
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.
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