141–150 of 252 posts
Let me guess: the catch is the high maintenance cost of the piston engine.
It's not real until it's in Microsoft Flight Simulator 2020.
As awesome as the new Flight Simulator is, as an avgeek the Flight model is very disappointing. X-Plane can, and has, been used to design real world aircraft because you input the aircraft geometry and it simulates how it should fly based on that. MSFS extrapolates a lookup table over the input geometry, making it useless for real-world aerodynamic predictions. From the consumer perspective, both models are capable o…
I wouldn't be surprised if their blade element theory approach is superior to whatever Microsoft is doing (not familiar), but still both of those are optimized for realtime simulation, not for correctness.
When I wanted to analyze performance of a hypothetical rigid wing hang glider I went with XFLR5. That isn't a perfect tool by any means either but its algorithms should be miles ahead of X-Plane. Though of course you can't actually fly the plane in XFLR5, just do the math.
Bill Lear did it first: https://en.wikipedia.org/wiki/LearAvia_Lear_Fan Success is dependent on the gearbox.
> Success is dependent on the gearbox. This uses a single V12 Diesel engine. The Lear Fan used dual turboshaft engines.
And the speed figures are hard to believe for just 500hp, and an aircraft of this size.
What is on the photo make me think they have 2 of them, mounted at 120 degrees.
It seems a bit dishonest to compare it to a jet, when the obvious competition is a single engine Turboprop like a TBM or PC-12. On paper it beats those aircraft, but by a far less impressive margin when you consider engine TBO, which is currently 1250 hrs on the EASA cert. With the inherent unreliablilty of piston engines, a PT-6 might look more appealing. I'd love to see this aircraft come to market, but I fear it m…
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Sorry for the amateur question, but why does it take longer to take off in hot places? Doesn’t heat generate lift, like in gliders crossing hilly terrain? Or is it the heat offsetting with the cooler ground that helps, so you’d need a greater amount in hot places?
When it is hot out Air is less dense so the wings don’t generate as much lift. I believe engines make less power when the air in is hotter too as there is less delta T. Something something Carnot cycle
For airplanes take-off, the lift is the issue I'd say.
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TFA did not say maximum speed 450mph, it said "maximum cruising speed of at least 450mph" Still doesn't mean it gets 18-25mpg at 450. If it can realistically do half of 4500 miles at 450mph, there are a lot of interesting routes (Gets you as far as Tel-Aviv from London, Boston to Phoenix, or Los Angeles to Miami). Using that completely-pulled-out-of-my-ass number of half the range at 450, and assuming quadratic drag,…
$5k plus pilots (I’d want two for a transatlantic flight). And you’d still be stuck inside a very small space for 12 hours, with what’s likely to be a porta-potty level lavatory and minimalist galley. Oh, and a single piston engine, which is less reliable than turbines, over a lot of very cold water. Not sure that would be the best use case for this plane.
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Much of the improved efficiency comes from the engine[1], which claims "50% lower fuel burn compared to turbine engines in the same power category". The engine company is German and so we can make lots of jokes about German companies' fuel efficiency claims I guess. Nevertheless, it has been around since 2012 and is used in a few planes already, so presumably there is some measurable improvement there or they'd have…
Still, a plane with half the aerodynamic drag and twice the BSFC is only getting 4x the fuel efficiency, not the ~10x they're claiming. Even if they're making a bit of "free" thrust from their cooling system (which has been a thing since WWII), I don't see what accounts for the rest, even ignoring that the Celera likely has a significant increase in frontal area due to the standing-height cabin.
That doesn't seem completely unreasonable.
A Pilatus PC-12 (which is the turoprop competition here) NXG gets around 4.3 mpg.
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The Piaggio II ( https://www.aircraftcompare.com/aircraft/piaggio-p180-avanti... ) is missing several modern aerodynamic and efficiency features like winglets and gets 15MPG and has a 1600 Mile range. Significantly beating it’s fuel efficiency at similar speeds seems reasonable just eyeballing the two designs. Getting the full 20MPG at 450MPH might be a stretch, but it’s not all that unreasonable. Also, higher aerody…
I’m not sure those mpg numbers are correct: the more fuel efficient Piaggio EVO update, with winglets etc, in the extended range version can hold about 450 gallons of Jet A and has a 1770nm range, so even with plenty of reserves that doesn’t get it anywhere above half of 15mpg (from what I can find IFR reserve comes out to 75 gallons, thus 4.72mpg nautical or 5.4 statute). Which is why the jump in efficiency would be…
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It is a V12. Historical military V12s had a feature of two bank redundancy. One row of 6 cylinders can be shut down along with its pumps, cooling, etc. And I have a big suspicion that they use two of these engines inside.
V* engines share a common crankshaft with both banks, that's the V part. Please cite any specific V12 aircraft engine that can have one bank of cylinders shut down. I don't believe one exists.
https://en.wikipedia.org/wiki/Multi-Displacement_System
https://en.wikipedia.org/wiki/Active_Fuel_Management
