From Hackaday:
Check out this video footage of this LED-adorned RC helicopter flying on a dark night. But this isn’t an art project. Analyzing the long-exposure photography turns out to be a great way of clearing up some of the physics of flight which otherwise are not at all intuitive. The helicopter used here has different colored lights on the nose and tail, as well as lights on the rotors.
Depending on how the aircraft is moving, different 3D spirography is captured by the camera. When you zoom in on part of the flight path it becomes clear that there are wider arcs on one side of the fuselage than there are on the other. This has to do with the forward progress of the aircraft and the rotation of the blades. The phenomenon is well known by helicopter enthusiasts, and accounted for in the design. But what we didn’t realize is that it actually translates to a theoretical speed limit for the aircraft. Our childhood love of Airwolf – the TV helicopter that could outrun jets — has been deflated.
You should remember the helicopter physics videos featured here last month.
Comments
http://vimeo.com/4710263
Supersonic, no problem! Just fold the blades back and fire up the rockets!!
But, nothing was as fast as theAirwolf. It was supersonic! ;-)
Huh, I didn't realize the Chinook's rated top speed was so close to the Lynx's. Very interesting. I should have done more research.
The Gazelle, another "fast" helicopter is rated at 193mph. Cobra 172mph. Apache 158mph. EC135 178mph.
There are a number of single rotor choppers that have speeds near the Chinook, but only the Lynx is faster? Considering how old the design of the Chinook is, that's really something.
BERP
Though I am sure there are other factors, I believe the reason he was stating that we should know that chinhook was fastest was due to the fact that the top limiting speed of the blade due to the speed of sound and pitch on the retreating blade.
Interesting fact, the Chinook has a wiki Max speed of 197 while a Westland Lynx (regular heli) has 201, though the Lynx has the fastest recorded topspeed for a helicopter of 247. The rated max speeds are not that different though. I'm curious if blade speed is really the limiting factor, as the chinook's blades are much larger and therefor would have less RPM though still providing huge amounts of lift. I really believe there are so many trade offs that its possible that at those speeds aerodynamics are key, the chinook having marginally more drag that it would overall reduce its topspeed at those airspeeds. Here is the Drag force equation, with the variables representing air density, velocity (notice that the force increased by velocity square, high speeds need much more power to overcome drag), coeffecient of drag (aerodynamic-ness), and then area.
But who knows.
@William, while technically correct, I'm not really sure that's the real, or only, reason. I say that because the Chinook is far from the fastest helicopter ever made. Many single rotors are faster. It could be more about horsepower, aerodynamics, loading, etc.
the Chinook has counter rotating blades so the gyroscopic procession of the blade stall effect on a single rotor heli is negated because the Chinook is supported symmetrically by opposite sides of the two rotors.
So, what's the physics behind why the Chinook is faster than an attack heli, like the Apache, I wonder. Is it just because it has two engines and two rotors?
I'd like to see an exec from Discovery or TLC explain to me why this guy doesn't have a show, and instead we get... well, all the crap they play normally.
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