
Flying Aquila: Early lessons from the first full-scale test flight - abhra
https://code.facebook.com/posts/268598690180189
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t413
This is the only article of original substance on the internet, everyone else
copied pieces from it. I still can't find an answer (or even anyone asking the
question): How does it land?

There's no landing gear, it takes off from a dolly, and it's only designed to
stay up for 'months at a time.' Does this mean it needs extensive repairs
after it crash lands on runways that are half its width? The ScanEagle UAS
also has no landing gear but is small enough to be caught by a cable mid-air
[1].

Having no journalists present for their test launch and only getting
officially produced videos and non-critical reposts is not enough.

[1]
[https://www.youtube.com/watch?v=w88uCC2Jv48](https://www.youtube.com/watch?v=w88uCC2Jv48)

~~~
mikeash
I would speculate that it lands on skids. Skids are pretty lightweight and
will do fine for landing, but you need a lot of power to take off with them
unless you're on ice or snow.

(You know your landing gear is up when it takes full power to taxi.)

~~~
anotheryou
good call. The U2 has only gears in the center and "skids" on the wings,
trying to get as slow as possible before they are needed (an some muscle car
following for guidance).
[https://youtu.be/hxFz6ImB8fI?t=165](https://youtu.be/hxFz6ImB8fI?t=165)

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Gravityloss
It seems to follow the Stanford Swift aerodynamic philosophy: low taper and
winglets.

This is different from the recent NASA Prandtl-d aircraft which is of the
Horten paradigm: lots of taper and no winglets.

It's possible the former is a lot easier to build, because of constant chord,
especially as a solar powered platform.

With batteries you can distribute the weight very well so designing for things
like wing root moment might not be the defining thing, instead some re complex
aeroelastic design criteria.

Very fascinating to see this resurgence of flying wing again, popping up in
many other places too.

~~~
ktta
I have no clue about half of the things you just said. Can you guide us, the
ones with less knowledge about aerodynamics-- to some resources which we can
watch/read? (preferably online and free, of course :) )

~~~
Gravityloss
See How It Flies at [https://www.av8n.com/how/](https://www.av8n.com/how/)
seems massive but it's written in a captivating way.

Basically in a wing, there's overpressure on the bottom and underpressure at
the top. This is all good. But it causes a problem at the wingtip, the air
escapes and goes from bottom to top. The tip vortex. Does not contribute to
lift, causes drag, so is bad.

So you can put a vertical winglet there to diminish the tip vortex, or to
extract thrust from it. Or you can extend the wing but make it have a lower
angle of attack near the tip, again extracting thrust, basically a horizontal
winglet if you will.

Then there's the issue of stability. A plane is stable when, if you increase
the angle of attack, the rearward lifting surfaces have more increase in
negative nose down moment than the positive nose up moment of the forward
lifting surfaces. So the aircraft tends to correct itself (move back to lower
angle of attack).

In an ordinary plane it means a wing near the center of gravity and a tail
with a lower angle of set incidence far behind.

In a canard, the center of gravity must be between the wings and the front
wing must be set in a higher incidence.

In a flying wing it means sweepback and twist: the outer portion of the wing
must act as a tail. The outer portion must be twisted nose down so it has a
lower angle of incidence.

Flying wing design is harder since there are more functions it must do than in
a more conventional plane.

That is a really really short version of it. It didn't mention positive moment
airfoils etc.

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abakker
Does it not include balloons? They want surface area, slow movement, and the
ability to operate on little to no energy. Wouldn't a large, permanent balloon
filled with helium and sized to perfectly offset the weight of the aircraft be
better? It seems like it would be easier just make it neutral buoyancy than to
try to constantly provide lift.

~~~
upofadown
>slow movement

But not too slow. You need to be able to stay on station when there is a wind.
You would need some sort of powered airship. To be better than a wing it would
have to have less drag.

~~~
abakker
I was wondering about that. Is 25mph cruise speed really going to be enough to
overcome wind anyway?

I suppose it could be both. Maybe inflatable fixed wing, if it had the right
dimensions.

~~~
anotheryou
Maybe they have some safety altitude so they can drop to lower altitudes with
other winds and come home when much wind is expected.

Clouds often move in another direction than the wind near the ground. (is that
some eddy current?)

~~~
mikeash
It's wind shear. Wind at altitude tends to travel at right angles to the
pressure gradient, as the coriolis force does its thing. Wind near the ground
tends to travel directly from high pressure to low pressure, because of
friction with the ground. That friction also tends to slow it down. Net
result, it's common for wind to turn and increase in speed as you go up.

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phillc73
Total brand confusion. There is already a well established manufacturer of
light aircraft called Aquila[1]. My initial thought was that they'd launched a
new model.

[1] [http://aquila-aero.com/](http://aquila-aero.com/)

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iamcreasy
It says the aircraft can stay aloft for 90 days. Why not longer? Regular
maintenance or they have to replace something?

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bigiain
<cynical thought>90 days? Thats just over 2^23 seconds. Wanna bet some timer
overflows a 3 byte signed int? Brings new perspective to a "crash bug"...

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andrewwhartion
Once they deploy these to the places in the world they want to, I wonder how
long it's going to take for one to be shot down.

[edit] I suppose though they fly high enough to be out of range of most
inexpensive weapons systems.

~~~
ChuckMcM
It would be pretty high up, although still reachable by fighters.

I doubt people in a friendly country would shoot it down, although I could
certainly see Iran having issues of someone flying one along the border
providing "free" Internet to people inside their borders. No doubt they would
be able to successfully jam it's electronics.

Perhaps more worrisome would be having these things fall out of the sky. Being
a long as they are, structural failure by suddenly overloading the wing might
turn them into the moral equivalent of the Maple Seed of Doom[1] on their way
down. Probably reasonably low risk in rural areas but something to think about
if they are taking off from airports in Kansas city for example to fly out
over the great plains.

It's that latter bit that makes me even more curious. In the write ups so far,
both the 'project loon' and the Aquila videos suggest this very expensive
piece of equipment is going to be flying over sparsely populated areas to
provide Internet. But with so few customers how do you cover the cost? Simple
economics would suggest you'd want to fly it over a really densely populated
city, then you would have a huge addressable market rather than over the corn
fields of Iowa or the back roads of Oklahoma.

It suggests to me that its easier to spend a million dollars operating a
couple of these over a small town than it is to get permission to pull a fiber
along the power grid. The latter is more of a policy issue rather than a
technology issue though.

[1]
[https://www.youtube.com/watch?v=r4urT74yq6c](https://www.youtube.com/watch?v=r4urT74yq6c)

~~~
evgen
If you are operating over a large and crowded area you are going to be facing
more competition for customers (from competitors that can use the population
density to justify the initial build costs of better infra) and you are also
going to be facing more spectrum competition and interference. While flying
over the corn fields of Iowa may not seem too useful, each plane could have a
relatively large footprint and could also be used to enable a lot of non-urban
IoT applications. Sell bulk bandwidth to precision farming equipment shops,
mobile applications in the area, and households poorly served by old copper
telco infra. Not necessarily huge bucks, but you could probably do it at a
cost that would crush competing data providers in that plane's footprint and
lock up a nice little revenue stream.

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amelius
If I read a story on code.facebook.com, will my status go to "online"?

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Sarki
So this plane is supposed to fly continuously without landing gear? I hope
they considered poor flying conditions lasting for weeks in their model,
things like heavy rain for a couple of weeks or even hurricanes. Sometimes
there's a good reason why the Internet is not yet available somewhere.

~~~
rosser
FTFA: " _Once they are fully operational, these high-altitude planes will stay
airborne for up to 90 days at a time..._ "

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signa11
imho, balloon seems to be a better idea.

~~~
1rae
You can get an aircraft to circle and act like a low orbit geostationary
tower, while a balloon is going to travel wherever the wind takes it.

