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-   -   Down the Rabbit Hole with Eviation's Alice (https://ecomodder.com/forum/showthread.php/down-rabbit-hole-eviations-alice-37648.html)

freebeard 07-10-2019 10:53 PM

Down the Rabbit Hole with Eviation's Alice
 
Wowsers.

https://www.youtube.com/watch?v=W0DHhiwvatQ

Check out the skin radiators at https://youtu.be/W0DHhiwvatQ?t=104 and consider the architectural advantage of an ME-262 shark-like shape to the fuselage for headroom in a small cabin.

Props positioned to accelerate the three wake-producing areas, with [high frequency] torque vectoring because landing can be tricky. At https://youtu.be/W0DHhiwvatQ?t=145 the rendering shows two- and three-bladed props.

So what do you think? How will they look with advertising all over them?

Piotrsko 07-11-2019 10:02 AM

Somebody needs to call bill lear, they stole his plane.

I think I will be optimistic/ skeptical until type certified and produced.

freebeard 07-11-2019 11:58 AM

The Lear Jet had two turbojets on the fuselage and a T-tail. ....and a round fuselage. I'm more reminded of Scaled Composites.

Piotrsko 07-12-2019 10:37 AM

LEAR FAN. Two intakes on fuselage, I believe a pair PT-6 turbo shaft inside, "Y" tail. The black engineering prototype was across the street from my old job.

Maybe your right, does have that scaled composites look.

NeilBlanchard 07-15-2019 09:53 AM

Pretty amazing plane!

samwichse 07-15-2019 10:41 AM

https://upload.wikimedia.org/wikiped...5953232%29.jpg

I mean, kind of? But also not really?

SC definitely does the non-tubular fuselage thing a lot though... nothing like this either, really.

https://www.armytimes.com/resizer/qx...XNI4APDZRQ.jpg

freebeard 07-15-2019 02:34 PM

https://en.wikipedia.org/wiki/Learjet#Timeline

I looked at the link I provided, there was a major redesign a one point. Isn't there some disadvantage to the V-tail? Maybe compared to Y- or T-tail?

There's airframe and there's power plant. Those skin radiators need a lot of wetted area.

NeilBlanchard 07-15-2019 09:36 PM

A V tail has less drag than a conventional tail, because there are fewer intersecting surfaces. A T tail is slightly lower drag, I think, because the intersections are farther apart? But the structural simplicity of the V tail gives it a bit of a weight advantage, maybe?

I am surprised a bit by the slim wings, and slender wing section.

The wing tip motor pods would seem to alleviate the vortex drag, I think?

samwichse 07-15-2019 09:47 PM

Quote:

Originally Posted by NeilBlanchard (Post 602106)
I am surprised a bit by the slim wings, and slender wing section.

I wouldn't be. If you're looking for maximum efficiency but not necessarily maximum speed.

https://www.soaringmuseum.org/images...dff71e856.jpeg

Or high altitude and maximizing dwell time on not much fuel.

https://www.extremetech.com/wp-conte...-in-flight.jpg

freebeard 07-15-2019 10:18 PM

https://duckduckgo.com/?q=aircraft+V-tail+disadvantage

Apparently less interference drag but more wetted area required. And more complicated control linkages.

It looks like all the air sees is high-efficiency airfoils and propellers sucking any detached airflow for lunch.

Piotrsko 07-16-2019 09:54 AM

Quote:

Originally Posted by freebeard (Post 602110)


It looks like all the air sees is high-efficiency airfoils and propellers sucking any detached airflow for lunch.

Hunh? Not sure what you mean here.

freebeard 07-16-2019 10:43 AM

I'm not sure either. :)

There're three prop circles that leave the mid-span of the wings and the tips of the tail exposed to free air. The fuselage and engine nacelles should have laminar flow, but any attached turbulence (interference drag at the root of the tail in crosswinds?) is actively managed by the propulsion system.

Maybe there is no advantage.

Piotrsko 07-16-2019 11:40 AM

Not to disagree, but most everything in front of the props should be pretty much laminar unless it is a huge profile change.

I can see some turbulence at intersections and with the tip setup from vortice flow, and I wonder about the drive units operating in disturbed air but that will just reduce available thrust and not decrease drag.

I defer to your knowledge base as mine is mostly deduced from my aviation failures.

NeilBlanchard 07-16-2019 12:28 PM

Quote:

Originally Posted by freebeard (Post 602110)
And more complicated control linkages.

The Alice is fly by wire, so the blending is done by the computer, and servos do the work?

redpoint5 07-16-2019 12:41 PM

What I've always wanted to see is at least 1 electric motor driving the wheels. Rather than needing a pushback, just use the electric wheel to taxi, and only spool up the engines at takeoff (or however long is needed to warm up before takeoff). Perhaps the extra weight isn't justified when there's plenty of infrastructure in place for a pushback, though that whole process takes a couple minutes.

freebeard 07-16-2019 12:54 PM

Quote:

Originally Posted by Piotrsko
I defer to your knowledge base as mine is mostly deduced from my aviation failures.

Ha! Mine is from lurking on Ecomodder. :)

redpoint5 07-16-2019 01:22 PM

Maybe it was the 100% fly by wire that made me think of this, but I just listened to "Bit flip" on Radiolab. Apparently the Toyota stuck accelerator issue was due to random bit flipping caused by cosmic radiation. At least that failure mode could be reproduced by simulating/inducing a bit flip in the speed control program. Now the system has redundancy to prevent such a problem (or make it statistically extraordinarily unlikely).

I'm sure an aircraft would have this redundancy built in, but with so much software, there's bound to be weaknesses in the code/redundancy/contingency.

Piotrsko 07-16-2019 01:50 PM

Quote:

Originally Posted by NeilBlanchard (Post 602145)
The Alice is fly by wire, so the blending is done by the computer, and servos do the work?

Afaik, Everything certified so far is redundant mechanical backup of some sort. Hydraulic mechanical actuation of surfaces. Im not sure the FAA is ready for full fly by wire with a multiple "souls" on board. A multi-million $$ fighter with nukes, they are ok with, as long as it has an ejection seat.

samwichse 07-16-2019 02:10 PM

Quote:

Originally Posted by redpoint5 (Post 602146)
What I've always wanted to see is at least 1 electric motor driving the wheels. Rather than needing a pushback, just use the electric wheel to taxi, and only spool up the engines at takeoff (or however long is needed to warm up before takeoff). Perhaps the extra weight isn't justified when there's plenty of infrastructure in place for a pushback, though that whole process takes a couple minutes.

https://en.wikipedia.org/wiki/EGTS

freebeard 07-16-2019 04:15 PM

Quote:

The main landing gear is equipped with an electric motor powered by the auxiliary power unit which allows the aircraft to push back from the gate and taxi without a tug or its jet engines.[1]

The system weighs 300 kilograms (660 lb) and is permanently installed on the aircraft.
So, the weight of 2-3 passengers. :)
_______________

Quote:

Originally Posted by DDG
What does 'triple redundant closed-loop digital avionics ...
https://space.stackexchange.com/ques...cs-system-mean
The primary flight system comprises six computers, three sets of two computers each (triple redundancy X dual redundancy). This, along with massive verification and validation (V&V) was enough to satisfy NASA that the Dragon achieves the two fail safe requirement.


redpoint5 07-16-2019 04:49 PM

Quote:

Originally Posted by samwichse (Post 602160)

How did you know about that?

I had the idea while waiting for a delayed tug to push us back from the gate. The whole process takes longer than necessary for such a routine task. Then we have to wait a moment for engines to start and come up to operating parameters before we get underway taxiing.

My other idea was autonomous ground robots that shuffle planes around, but then that would double the amount of driving traffic on the taxiway. It would eliminate accidents caused by encroaching on a runway in use though, and since it's automated, tighter time and spacing tolerances can be maintained.

Piotrsko 07-16-2019 05:03 PM

Only downside to robotic tugs is wing tip rash in crowded airports taxiways if someone didn't park in the correct bay. Talk about ruining your day because everything gets parked until the Feds reapprove the movement.

A lot of time waiting is for tower/ground approval to start. Heck, I even had to have permission at some airports.

aerohead 07-17-2019 10:38 AM

runway
 
Quote:

Originally Posted by redpoint5 (Post 602176)
How did you know about that?

I had the idea while waiting for a delayed tug to push us back from the gate. The whole process takes longer than necessary for such a routine task. Then we have to wait a moment for engines to start and come up to operating parameters before we get underway taxiing.

My other idea was autonomous ground robots that shuffle planes around, but then that would double the amount of driving traffic on the taxiway. It would eliminate accidents caused by encroaching on a runway in use though, and since it's automated, tighter time and spacing tolerances can be maintained.

Wait 'til a low-time student pilot lands on top of you during takeoff!
That happened to the Cherokee my brother flew out of Van Nuys Airport,California.He wasn't in the plane at the time,but it was the end of it,chewed rear-to-forward.Nut behind the yoke!:p

Piotrsko 07-18-2019 10:11 AM

Van nuys is just massive scary, any way you look at it.

Joenavy85 07-18-2019 12:59 PM

Quote:

Originally Posted by Piotrsko (Post 602142)
Not to disagree, but most everything in front of the props should be pretty much laminar unless it is a huge profile change.

I can see some turbulence at intersections and with the tip setup from vortice flow, and I wonder about the drive units operating in disturbed air but that will just reduce available thrust and not decrease drag.

I defer to your knowledge base as mine is mostly deduced from my aviation failures.

A "puller" prop gives you more efficient propeller operation due to it grabbing nice clean air. A "pusher" prop gives you lower propeller efficiency due to the relatively "dirty" air flow.

The airflow will be laminar for the most part, but when the air rejoins after going around the wing it isn't perfect.

A benefits of clean airflow around the fuselage on a "pusher" is more beneficial than the clean air being grabbed by a "puller". The downside is that, even when fly by wire, the control systems are more complex, as well as the balance being more difficult to fine tune.

redpoint5 07-18-2019 01:40 PM

Quote:

Originally Posted by Piotrsko (Post 602178)
Only downside to robotic tugs is wing tip rash in crowded airports taxiways if someone didn't park in the correct bay. Talk about ruining your day because everything gets parked until the Feds reapprove the movement.

A lot of time waiting is for tower/ground approval to start. Heck, I even had to have permission at some airports.

I was thinking in terms of large/busy airports. There'd be no rash if everything was automated. The tugs would know the dimensions of their aircraft, and know how to shuffle them around without collisions. Perhaps the tugs would do the taxi in too. That might be better than returning to the gate empty handed anyhow, as it reduces ground traffic.

The John Deere I drove had GPS steering. I had to make the figure-8 turns at the end of the rows, get within 18" of the upcoming row, then push a button to give control back over to the automation. Similar principles would apply. Tug needs the plane to be within a defined space, or it is going to refuse to play.

freebeard 07-18-2019 05:40 PM

Quote:

Originally Posted by myself
It looks like all the air sees is high-efficiency airfoils and propellers sucking any detached airflow for lunch.

Joenavy85 — That was my point, the laminar flow can approach perfection, and the props are there as a backstop.

The wingtip nacelles are radiators first for cooling efficiency. The torque vectoring in yaw is just gravy.

Now all it needs is an electric tail wheel.

euromodder 07-20-2019 07:41 AM

Looks a lot like a pusher-variant of the Bugatti 100p

https://www.flitetest.com/articles/t...ime-here-s-why

If one of the tip-engines fail, asymmetric thrust errrrr..... push may well come an issue
Thats a big moment arm !

freebeard 07-20-2019 10:34 AM

It's not a blended body, but the Buggati was cool. I think of the Vought XF-5U. No fuselage at all, but it has the wingtips propellers.

https://upload.wikimedia.org/wikiped...ought_XF5U.jpg


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