Inspired by this thread about the wingspans of pegasi and alicorns.

Hey guys, let's discuss how illogical pegasus flight is.

For example, nobody ever seems to realize that pegasi don't have any rectrices—the tail feathers used by birds to brake and steer in flight. Pony tails aren't useful for those purposes at all, so Pegasi don't have this nor anything remotely similar to it by all appearances, and shouldn't be able to control themselves while flying. And while this would explain why Rainbow Dash seems to crash so often (high maximum speeds + lack of fine maneuvering + lack of aerobraking = only real way to slow down is "lithobraking"), it wouldn't explain her agility feats... nor how she or any other pegasus manages to fly at all.

Nameless Opponent: "But what about bats? They don't have those tail feathers and they can fly just fine, so pegasi could possibly fly!"

Ah, but bats DO have what is known as an "interfemoral membrane", AKA the uropatagium, a flap of skin which stretches between the rear legs and tail that serves the same purpose as a bird's rectrices.

Anybody in this group specialized in aerodynamics and/or ornithology-related topics? If so, feel free to speak up.

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Pony tails aren't useful for those purposes at all

I must disagree with you on this point. Regardless of how you look at it, their tails are going to cause a lot of drag. This ensures that the aerodynamic neutral point of a flying pegasus stays behind the center of mass. It's the same principle that the feathers on an arrow and the stabilizers on an airplane work on. Just because it doesn't look the same doesn't mean it can't serve the same purpose. As long as the pegasus has at least some control over their tail movements, they will be able to control their flight.

Edit: As a side note regarding Rainbow Dash specifically, maybe her tail somehow produces less drag than the average pegasus. Less drag means she can fly faster, and having a neutral point closer to her center of mass would make her more maneuverable, but it would also make her less stable and more prone to (ahem) hard landings.

Edit2: My bad, It's been a long semester, and I somehow got the term aerodynamic center confused with neutral point.

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2188389

...Something tells me that tail isn't helping much in terms of aerodynamic performance, but I can't quite put my finger on it...

Oh, it's probably how the tail isn't acting like a control surface whatsoever?

Look, even if we consider the evidence supporting the idea that they have strangely prehensile tails, it doesn't appear that the tail would actually be capable of controlling a pony's flight attitude in any meaningful way.

Tail feathers are analogous to the rudders of ships and boats—they help them steer and maneuver while flying, as well as provide stability as they take-off and land. By twisting its tail, the bird can change its direction mid-flight. To help the bird slow down, the tail flares out downward, creating more drag and decrease the bird’s velocity. The tail also helps the bird balance when it is perched on a branch. And while the bird is soaring, it can spread out its tail feathers behind it to create additional lift and stability. This works mainly due to a variation of delta wing theory (still being discussed, since standard delta wing theory doesn't seem to be adequate for bird flight) and something known as the Norberg mechanism (at slow speeds and high angles of attack).

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Me: Promoting intellectual discussion about a topic within a group specifically tailored to intellectual discussion.
You: Dicking around posting troll images.
Just a question—if you're not going contribute intelligently to discussions, why are you even here?
...C'mon, guys.

2189055

Me: Promoting intellectual discussion about a topic within a group specifically tailored to intellectual discussion.
You: Dicking around posting troll images.
Just a question—if you're not going contribute intelligently to discussions, why are you even here?
...C'mon, guys.

For our entertainment, of course.

2189055

Hey guys, let's discuss how illogical pegasus flight is.

I think one reserves the right to have fun in a thread when the topic at hand has already been established as illogical.

2188214
Well, I'll be brutally honest.

Pegasus flight is physically impossible without the aid of magic. They're even less aerodynamically sound than bumblebees.

2189055
All that picture accomplishes is to confirm that animators are not aerospace engineers. Even if their tails are as useless as a bundle of streamers for producing pitching and yawing moments, they still serve to produce aerodynamic stability in straight and level flight.

Your argument appears to assume that only a tail can serve as a control surface. While it may be the most effective means, it is not the only one. Other possible means of control include adjusting the angle of attack on their wings as well as head and leg movements.

Regardless of whether or not their tails can help them fly controllably, their wings are too small to achieve flight anyway.

I like to think that a pegasus' wings have inherent magic which allow them to lighten themselves and anything they're carrying. It could be a variant of unicorn TK that pegasi can do innately.

I'm not an aeronautical engineer, but if one wishes to disregard the magic aspect, perhaps the legs can be used to help control flight? No birds have four massive limbs; they've got stumpy little stick-feet.

2189331

less aerodynamically sound than bumblebees

Here's another thing I feel I must dispute. Bumblebees (and other insects, for that matter) are not aerodynamically unsound. The discrepancy arises because when analyzing the flight characteristics of a bird or aircraft, we base all our equations on a set of assumptions called the continuum hypothesis (which was lesson 1 in my fluid mechanics course (why yes, I am studying aerospace engineering)). That set of assumptions works for everything from small birds to jumbo jets, but it breaks down when you go down to the scale of an insect wing, so you have to use a different set of governing principles to properly analyze the aerodynamic characteristics of a bumblebee.

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Neat!

2189331
Well, that much is obvious—hence the opening line "hey guys, let's discuss how illogical pegasus flight is."

2189381

All that picture accomplishes is to confirm that animators are not aerospace engineers.

...Too bad what they produce is canon, and anything made by aerospace engineers to correct them would be headcanon.

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Your argument appears to assume that only a tail can serve as a control surface. While it may be the most effective means, it is not the only one. Other possible means of control include adjusting the angle of attack on their wings as well as head and leg movements.

I'm not an aeronautical engineer, but if one wishes to disregard the magic aspect, perhaps the legs can be used to help control flight? No birds have four massive limbs; they've got stumpy little stick-feet.

If I had the resources and facilities to test this, I would so do it. However, based on what I do know, I believe this method would likely be pretty unstable in flight, especially at high speeds.

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There is also the fact that many flying insects use a different model of aerodynamics from rigid wing craft and avian flight. The mechanics are still not fully understood. However, I can tell you that it doesn't match avian flight at all.

On that note, what would have to be changed to actually make it possible for them to fly, even factoring in "magical assistance" like artificial aerodynamic drag and weight reduction? The rational exponent equation for bird wingspan "L=2.43*W^0.3326", where "L" is wingspan in feet and "W" is weight in pounds, may be of some help. What also may be useful is the fact that it asks for weight, not mass, so gravitational acceleration is a potential variable to consider.

2188214

"Magic" Mutherfucker. Embrace that shit... Nah man it's jut one of those cartoon things

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The scene which summed up pegasus flight for me is in 'Party of One', when Fluttershy and RD both hover mid air, daintily waving their wings, chatting with Pinkie.... and then at the end they both rocket skyward.

The way they can fly inside the library without (necessarily) disturbing papers on the floor kinda suggests it has nothing to do with differential air pressure.

Given the walking on clouds thing, maybe pegasi can make patches of air solid (with a certain elasticity, somehow coupled to the ground) and fly by pushing against temporary supports with their wings, and hover by letting their wings bounce up and down on a springy invisible support. This theory could explain how Rainbow Dash managed to rebound from her shock cone in 'Sonic Rainboom'.

Or maybe they just fly by magic and the wings and tail are just for decoration.

2188389 I think her tail is too flexible to provide ample control; the only rigid, controllable part is the base of the tail, meaning the the rest of the tail would really just flap around uncontrollably.

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Personally, I've hypothesized that the "Sonic Rainboom" (and pegasus flight power in general) is a derivation of the same power that allows Pegasi to interact with clouds and manipulate weather, something within the domain of "innate atmosphere manipulation". I'm thinking that RD's ability to accelerate to supersonic velocity might be due to a process of taking in air at high velocity, somehow creating an envelope of compressed air around herself that streamlines her drag coefficient to aerodynamically-minimal levels akin to the Sears–Haack body model (seeing as her body is about as aerodynamic as... a misshapen horse), then accelerating herself by propelling this compressed air rearwards in a manner of jet propulsion. This is how she accelerates to sonic speed without flapping her wings—they would ultimately slow her down at this speed, so she would hold them close to her to reduce the drag they produced.

While it's certainly not perfect, it's a better hypothesis than most can offer. How she manages to produce enough thrust with this method is beyond me.

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Seems a good hypothesis for high speed flight, although we need something else to explain slow speeds and hovering.

You may like my story: Rainbooms and Rationality

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I think I may be onto something. What if the atmosphere were notably thicker?

2210867
It's definitely possible. It would allow smaller wings to produce more lift.

As a side note, holding other atmospheric variables constant (pressure, viscosity, etc.) would imply a lower temperature (ideal gas equation shows T is proportional to pressure/density), which would in turn imply a lower speed of sound (not by much, but still...).

22108670

What if the atmosphere were notably thicker?

I think that would put an much lower upper limit on theoretical top speed (which may not be an issue, since there's no point of reference other than the show itself). It might also provide a convenient explanation for why clouds seem so substantial, and why wings are so small. It would provide justification for the thick legs that ponies have, and possibly why they can have such large heads.

It also suggests that a human in Equestria who was not wearing appropriate gear might be crushed by the atmosphere, would probably move in slow motion, and quite likely would get a fatal case of the bends as soon as he returned to earth.

Now I want to write a story with this premise

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I KNOW RIGHT? Esker's thick atmosphere hypothesis solves everything! This also explains why gigantic creatures like dragons can exist in Equestria!

Also, dinosaurs were giant because the atmosphere was 500 times thicker than it is today during the Jurassic, so buoyancy reduced the strain of gravity on their bodies! It all makes PERFECT sense and breaks no physical laws! It's a flawless hypothesis!

......LOL, impossible crackpot science. But, crazy as that hypothesis is, it did give me this idea, which looks like it has potential to solve a lot of problems...

Now to figure out just how thick it would have to be, and if it is even physically possible to have an atmosphere that thick... because Esker's notion of 670 kg/m^3 atmospheric density is not possible on Earth, even using tungsten hexafluoride, the densest gas at STP, as the sample gas—it simply wouldn't be gas anymore, having long shifted phases into a superfluid (or some other strange rarely-seen state of matter) at such high pressures and temperatures (>14,000 K, anyone? Even I'm not sure I calculated that one right).

2211294

With a larger planet, though, even an atmosphere like ours would be denser. I presume there's an upper bound, though.

Equestria could also have higher gravitation for some other reason ....

With the tungsten hexaflouride atmosphere, the human wouldn't have to worry about the bends when he got back home.....

2211610
I think the upper bound is probably when gas laws tell you that the gas is going to be >14,000 Kelvin when at 51 atmospheres.

I think that's well past "quitting time". Like I said, I'm pretty sure it wouldn't even be a gas anymore.

2211294
*reads about Esker's hypothesis*
Yes, let's solve one set of problems by creating ten more

In all seriousness, I don't think you can get away with a density higher than maybe 2 kg/m^3 (if that) for atmospheric density. Any higher and the other variables I mentioned before will have to change or break physics as we understand it.

Although, if Equestria could be considered a parallel universe, the fundamental physics of that universe could be different from ours (magic immediately comes to mind). On the other hand, it could be part of our universe as well, and magic would fall into the category of 'dark' energy that, according to mathematical calculations, must exist, but we just haven't figured out how to detect, manipulate, or even interact with in any meaningful way.

... Yeah, I'm gonna stop now

2210867 It would slow her down. And it won't solve the problem of her lack of tail control.

2210867
Well, the density of the Equestrian atmosphere is easy to calculate by applying Archimedes principle (under certain assumptions).

Pinkie is balanced by the air displacing by 6 balloons. So neglecting the weight of the gas inside the balloons, and modelling Pinkie as a spherical pony, we get

density(air) = density(Pinkie) * radius(Pinkie)^3/(6 * radius(balloon)^3 + radius(Pinkie)^3)

From this I estimate the air density is about 3 milli Pinkies per cubic hoof

For (1 Pinkie = 100kg, 1 hoof = 0.1m) that gives 320kg/m3
Or if you prefer Plushie scale (0.2kg, 0.02m), 80kg/m3

So yes, it's notably thicker. Unless of course Pinkie is using her ability to change her acceleration due to gravity at will.

.

2220330

lack of tail control

Not a deal-breaker.

2224556 That still has elevons and rudders, something that a pony's anatomy can't make up for.

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Calculation featuring Pinkie Pie in a comedic scene?
—Instant skepticism.

2224556
As Assoe said, it's a deal-breaker if the aircraft has control surfaces, because that's the actual issue here—lack of proper control surfaces on pegasi.

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You don't need a one-for-one match with aircraft control surfaces to have stability and control in flight. Think about what ailerons, elevators, rudders, flaps, and so on actually do. All they do is change the geometry of the aircraft in a way that causes it to go the way the pilot wants it to. This can be accomplished with head movements, leg movements, etc.

And don't forget about articulating wings.

their legs don't seem like they can utilize lift. At best, they can be used as rudders, but their flight pose would look very awkward, with legs outstretched at their sides.

2228652
Their legs don't need to generate lift, and they don't need to be all the way out to the side to create a reaction. In fact, putting their legs out that far sounds more like a mid-air braking technique. If all they want to do is change direction, it would be easier to shift their head in the direction they want to go while curving their back slightly. It wouldn't take much, because the goal is to create an asymmetric aerodynamic profile. Big movements would actually be more likely to cause loss of control.

Edit: Fun fact, the lift produced by the main wings on an airplane causes a significant nose-down pitching moment on the aircraft. Because of this, the horizontal stabilizer actually produces negative lift to compensate.

2228837 That would seem like a very narrow flight path, meaning that Rainbows' stunts would not be able to occur.