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There is a mention of Ehang in the article. However, I cannot put this more succinctly: The Ehang is an abortion of aviation. Instead of going into the idiocy
by wanderingjew 9y ago
There is a mention of Ehang in the article. However, I cannot put this more succinctly: The Ehang is an abortion of aviation.
Instead of going into the idiocy of an autonomously piloted passenger aircraft (which will never be legal under any sane civil aviation laws), I'm just going to go over why the current Ehang 184 doesn't make any sense.
The Ehang 184 is an octocopter, with two rotors stacked on top of each other. It looks like a quadcopter with single person pod in the middle. So far, so good. However, on every aircraft ever, there are red nav lights on the port side, and green navigation lights on the starboard side. The Ehang places green nav lights in the back, red in the front. This makes sense if it always flies sideways. There are no anti-collision lights on the top or bottom, and therefore there's no way to tell when it's safe to approach the aircraft. Keep in mind, that's just the lights. There's far more wrong with this aircraft.
The battery life is 23 minutes, and the FAA requires 15 minute reserve under VFR conditions. That leaves eight minutes of actual flying time round trip. Since the Ehang needs to get back to a charging point, you're always four minutes away from your destination. Since the speed is 100km/h, the maximum possible distance the ehang can fly is about three miles, less if you account for slowing down, speeding up, and landing. Just walk it at that point.
The mere mention of the Ehang 184 in the NYT piece deserves shame. It is not a product, it has no basis in reality, and its place in history is alongside the old-time stock footage of 18-winged planes collapsing in on themselves. It is an idea so supremely idiotic the inventors and marketers of this device should be shunned.
- golergka 9y agoFrom your description, it sounds like a solid prototype: fix the lights and other typical prototype stuff, wait for battery technology to catch up, which a LOT of companies around the globe are betting on, and here you have a flying car.
- beaconstudios 9y ago> wait for battery technology to catch up battery energy density improvements are very small and incremental. It'll take decades to go from 23 minutes airtime to something even slightly practical.
- FabHK 9y agoFrom what I gather, battery specific energy has grown by 4% to 8% per annum, so doubling every 18 to 9 years. Applications in aviation (beyond tiny niche markets) would thus seem two to three decades away.
- beaconstudios 9y agobatteries will likely see a similar drop-off to Moore's law as they approach physical or practical limitations on energy density.
- FabHK 9y agoFurthermore, unfortunately, they never approached Moore's-law-speeds anyway!
- nradov 9y agoCurrent FAA regulations for rotorcraft require a 20 minute fuel reserve under VFR conditions. So wouldn't that leave only 3 minutes for useful flight? https://www.law.cornell.edu/cfr/text/14/91.151 https://www.law.cornell.edu/cfr/text/14/91.151
- FabHK 9y agoHaha, fully agree - vapour ware, from a toy company. But they claim they'll be operating a taxi service in Dubai this July, in 3 months! Let's see... The battery life issue (vis-a-vis reserve requirements) is common to all electric VTOL aircraft, and can be mitigated: Batteries will continue to improve (though probably slowly), and regulation seems to transition from strict specification-based rules ("x minutes reserve") to performance-based rules ("enough to ensure safe landing"). Yet, I dislike the eHang 184 particularly for the irresponsible marketing with lots of hype but few facts, the rotors placed to break your knees, the lack of redundancy, etc. I'm somewhat more positive on the Volocopter (disclaimer: I've invested 1000 EUR via crowdfunding) - what do you think of it?