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Helicopter Crashes While Filming Autonomous Audi
telomerewhythere writes "A helicopter commissioned by Audi to film its autonomous Audi TT climbing Pikes Peak crashed early this morning. Four people on board were hurt, the pilot seriously. It's a surreal story — a manned vehicle crashes while the one climbing a mountain driven only by computers and sensors carries on. Here's more on the autonomous Audi, a project undertaken with the help of Stanford University."
Your $70 GPS addon is way too inaccurate for the kind of autonomous navigation they're trying to achieve. I mean, your standard SiRFstar III claims 2.5 meters of accuracy 50% of the time (a sigma of 3.7 m). That means you can't even be sure whether you're actually on the road, never mind what lane you're in. And that's only in a clear-sky situation. Once you're in a downtown "Urban Canyon" where you hardly pick up any GPS satellites anymore or get wrong readings due to multipath propagation, good luck. Your standard GPS SatNav simply always assumes you're on the road. That won't do for an autonomous vehicle.
You'll need something closer to this high-speed INS+GPS, the better models of which can be accurate in the decimeter range (assuming careful calibration). The ones I know about are all in the US$50,000 and above price range.
I think the reason is that on a small scale, it is possible to control a quadcopter or quadrotor by changing the relative speed of the rotors, which is much simpler because there is no cyclic pitch, or swashplate mechanism, but this technique doesn't scale well. On a man-sized quadrotor, it would be difficult to accelerate and decelerate the rotors fast enough to have agile control, and so the use of cyclic pitch becomes the better method to control thrust. If you are using cyclic pitch, then it becomes simpler to have one (or 2) rotors instead of 4. Also, when a rotor tilts, it generates large gyroscopic forces. On a small model, these are small compared to the strength of the rotors, but on a man-sized vehicle, the rotors need to be able to "flap" in order to reduce stress on the blades, which again is simpler if you only have to deal with one rotor.
Wrong. Simply put, the elevation of the location and the service ceiling of the helicopter itself have nothing to do with each other.
The actual "Service Ceiling" of any aircraft is dependent on the local "Density Altitude" and not the physical elevation of the ground. Depending on the temperature, humidity and other factors, the density altitude of a particular location can be several thousand feet under or above the actual local elevation. The pilot would take that information into account to determine how high they can safely fly the aircraft.
Bill
It's my Sig and you can't have it. Mine! All Mine!
The helicopter crew is out of hospital. All four of them.
Oh for mod points - fellow rotorhead here. There's so much that could have gone wrong. Without more info it's just speculation at best.
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Well, since we have historical weather data for the area available, it isn't hard to guess what the density altitude would be. Looking at weather reports for the 17th from stations in the area, temperature rose pretty quickly once the sun was up. The article says early morning, but without a more exact time the quick temperature swing makes it harder to pin down.
At any point after 8am, the temperature profile looks to be quite a bit above standard atmosphere, meaning density altitudes were higher than pressure altitudes. Barring some unusual atmospheric conditions the density altitude at around 10,000 feet was probably closer to 12,000-14,000 depending on how high the temperature got at the time of the accident. The pilot underestimating the quickly rising temperature may have even been a factor.
If 11,000 feet is in fact the correct value for the service ceiling of the aircraft, I would say this situation was caused by the decision to fly a heavily loaded aircraft outside of its performance envelope.