4 ms·
> What's weird about mounting propellers at the end of the wing is that you lose half the lift of the propeller wash over the wing, over a normal placement. Bu
by audunw 7y ago
> What's weird about mounting propellers at the end of the wing is that you lose half the lift of the propeller wash over the wing, over a normal placement.
But it's pretty obvious that they don't have a problem with lift during cruise, so why does it matter that you lose some lift? I really doubt they would design the wing that narrow if simulations showed that lift was an issue, and I think these guys know what they're doing, so if you think this is an issue I think you need a stronger argument.
That's the whole point of the small propellers, to gain that lift during take-off and landing, while not producing drag during cruise.
> And we know from the Osprey that complex propeller systems fail too often. A dozen propellers means an order of magnitude more inspections, replacements, ground time (AOG), etc.
But we're already seeing from small electric planes entering the market now that they have much lower maintenance and operational costs. Electric motors are fundamentally more reliable and low-maintenance than other alternatives.
So it can make sense to spend some of those saved costs on increasing the complexity a bit to increase efficiency and redundancy.
I also don't agree that this propeller system is complex or would require an order of magnitude more inspections. As mentioned, electric motors are extremely simple and reliable, and the small propellers have a high degree of redundancy, so you could design the system to allow for failure of one or two motors without affecting operations. The folding mechanism for the propellers looks to be very simple.
A way to think about it could be: ensuring that you have high enough safety margins require a certain amount of complexity. You can either spend that complexity on two engines that require a high degree of internal complexity and maintenance, or you spend the complexity on 10 motors that are extremely simple and are allowed to fail.
I also think the comparison with the V22 Osprey is extremely flawed. The purpose of those complex rotors have an entirely different purpose, and it's certainly not for redundancy or efficiency, and the engines have wildly different properties from electric motors.
> Additionally, there is no "urban air mobility market" in the USA, and never will be, due to regulation and insurance requirements.
It's pretty bold to say "there never will be". But anyway, it's just a vision, something to strive for.
What we do know is that it's very likely that electric planes will lead to higher utilisation of small airports. They're cheaper to operate and more silent, which significantly reduces the barrier to using these kinds of airports. At first we'll just see pretty standard looking electric planes in existing small airports, but as this market grows, I think you'll see both the planes and the airports change to optimise for this new/growing market. No, maybe you won't have a flying car in your garage, but I find it very likely that you can drive/bike/walk to something like a bus/train-station to catch a small 10-20 passenger plane somewhere. And though that would be impossible with the regulations today, the regulations will adapt iteratively, allowing the small airports to move closer and closer to urban centres, with shorter and shorter runways.
- redis_mlc 7y ago> it's just a vision, something to strive for. There's no path to that vision in US urban areas. New airports will not be built near urban centers due to lack of land and NIMBYs. So you have a significant last mile problem. Everything seems possible when you don't know anything.