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."

Surreal

[dimethylxanthine]

It's a surreal story

No, it's just a clever PR stunt by machines from the future.

Something smells fishy...

[Type44Q]

I believe this to have been a joint false-flag operation conducted by Intel, the NSA and VW/Audi, to convince us that we should relinquish control of our Quattros to the machines. I knew there was something suspicious going on when they replaced the five-cylinder with a V6, but no one would listen...

Re:GPS?

[morgan_greywolf]

Or is this "GPS" actually much more than a GPS -- something more like an aircraft tracking computer?

Probably they were using something like that. Something along the lines of an inertial measurement unit (IMU) or similar navigational computer. These things usually combine GPS tracking with a precision gyroscope. They can pretty much fly a plane all by themselves, and the military uses them in land-based vehicles, such as autonomous or semi-autonomous tanks. That they could be used to drive a car is not surprising.

Re:GPS?

[mindriot]

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 [oxts.com], 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.

Re:Surreal?

[Anonymous Coward]

Correction: Un hélicoptère

Physics is a bitch

[Anonymous Coward]

The elevation at the crash site: 13,800ft

Service ceiling of the helicopter 11,150ft

The data is taken from Eurocopter AS355F2, the crashed one was a AS355F1.

Re:So the weak point in the system is......

[ceiling9]

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.

Re:Physics is a bitch

[wjsteele]

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

Re:Condolences

[gavron]

Correction... while the color scheme looks like their new Bell 212HP... it appears that this is actually an Aerospatiale Astar 355 ("Twinstar") dual turboshaft operated AS350 series aircraft.

E

All helicopter crew released from hospital

[Animats]

The helicopter crew is out of hospital. [jalopnik.com] All four of them.

Re:The opposite

[Kell Bengal]

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.

Re:Physics is a bitch

[tweak13]

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.

Re:Physics is a bitch

[tweak13]

Air temperature then was still close to the low for the night, around 50 degrees. While this is a lot cooler than the 90 degrees eventually reached that afternoon, it is still well above the standard atmosphere, and still clearly puts density altitude above pressure altitude. Atmospheric pressure was very close to standard, by the way, so there was no boost in density there.

Of course, these weather stations all measure temperature at the ground, most around 6000 ft. So let's look at this another way. In order for the air at 13,000 ft to be at a density altitude under 11,000 ft, it'd have to be at about -20 degrees. The normal lapse rate is around 3.5 degrees per 1000 ft. Thus, the expected temperature given 50 degrees at 6000ft is around 25 degrees at 13,000 ft. Unless the lapse rate was more than double the standard atmospheric model, the density altitude places that helicopter above it's service ceiling.

If I had to guess, I'd say that even in the early morning cool temperatures, that aircraft was still being operated in excess of its expected performance.