Why learn aerodynamics?

TDGlider said:
Sometimes, the most difficult student question to answer is "why do I need to learn this"? One of the topics where I struggle to answer this question is aerodynamics. Why do pilots need to understand how a wing creates lift according to Bernoulli or Newton? Many of us learned an explanation of lift based on the equal transit time theory, which is demonstrably false. Yet, we have been able to control our airplanes fine. I was also taught an incorrect explanation of why airplanes with dihedral have lateral stability. Even though I believed this incorrect explanation for years, I had no trouble keeping the wings level. If one can function well as a pilot despite an incorrect understanding of a topic, that calls into question whether understanding the topic is actually important. So, what do instructors on this forum say when asked by students why they need to learn about aerodynamics.

I am not suggesting that we take this material out of the curriculum (except the parts that are false). I would just like to be able to give a better answer to the "why do I have to learn this?" question than "it is on the test".
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There is a whole lot more to Aerodynamics that just how does a wing create lift. That in itself may not be all that important. But other aspects about Aerodynamics that affect how the wing performs are very important in keeping you alive.
 
"Why learn aerodynamics?" ... you'll be able to participate in these discussions with a little more authority.
 
TDGlider said:
Sometimes, the most difficult student question to answer is "why do I need to learn this"?
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Curious. Do you think A&P mechanics should not have to learn basic theories like aerodynamics, as part of their training and education as well?
 
Just for the fun of it.
Hot off the press... Really- I'm still figuring out how to make this work.
CFD simulation of a balsa glider airfoil (50mm chord) traveling at 1m/sec at a 2.6 degree angle of attack.

Pressure field around the foil - more bluish: lower pressure. More redish - higher pressure.
1743434561413.png
Velocity - more redder is more faster.
1743435347112.png

Streamlines. White horizontal lines added to make it easier to see the flow curvature at a distance from the foil.
1743434624831.png

Haven't yet figured out how to extract forces from this stuff.
 
Capt. Geoffrey Thorpe said:
Just for the fun of it.
Hot off the press... Really- I'm still figuring out how to make this work.
CFD simulation of a balsa glider airfoil (50mm chord) traveling at 1m/sec at a 2.6 degree angle of attack.

Pressure field around the foil - more bluish: lower pressure. More redish - higher pressure.
View attachment 139480

Haven't yet figured out how to extract forces from this stuff.
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Thank you, Jim (Capt. Geoffrey Thorpe), for your model of the balsa glider airfoil and especially for the link to your YouTube channel and this great explanation:


This is a great example (flat symmetric thin airfoil) because anyone should be able to see that the lift is simply the difference between the average pressures on the top side and the bottom side and there is obviously net lift. One of the reasons to learn aerodynamics is help us to appreciate the beauty of all of this!
 
FastEddieB said:
The misconception here is thinking that two air molecules separated at the leading edge are somehow still “linked” so that the upper one “knows” it must speed up to rejoin the lower one. They’re not.

My working visualization is that there is a venturi formed by the wing and the undisturbed air that exists somewhere above it. That’s why it speeds up and the pressure drops, thanks to Bernoulli.
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My favorite wind tunnel video:

Less than two minutes but very informative. Here's a still clip of how the flow accelerates over the top and slows beneath:

1743439265768.png

From See How It Flies:

1743439375592.png

1743439431433.png

Kind of debunks the whole equal-transit-time baloney.

It's a really good website: https://www.av8n.com/how/
 
TDGlider said:
Sometimes, the most difficult student question to answer is "why do I need to learn this"? One of the topics where I struggle to answer this question is aerodynamics. Why do pilots need to understand how a wing creates lift according to Bernoulli or Newton? Many of us learned an explanation of lift based on the equal transit time theory, which is demonstrably false. Yet, we have been able to control our airplanes fine. I was also taught an incorrect explanation of why airplanes with dihedral have lateral stability. Even though I believed this incorrect explanation for years, I had no trouble keeping the wings level. If one can function well as a pilot despite an incorrect understanding of a topic, that calls into question whether understanding the topic is actually important. So, what do instructors on this forum say when asked by students why they need to learn about aerodynamics.

I am not suggesting that we take this material out of the curriculum (except the parts that are false). I would just like to be able to give a better answer to the "why do I have to learn this?" question than "it is on the test".
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Let me ask you a question, explain the difference between a shallow bank, medium bank and steep banked turn and why knowing these definitions has any importance to me as a brand new student?
 
I believe Bernoulli was a Plummer?

You can see his equation here -> http://hyperphysics.phy-astr.gsu.edu/hbase/bercon.html

In as much as air is compressible and thermodynamics gets involved you are on the edge of a deep rabbit hole.

I think of the physics as mathematical models useful for predicting the behavior of things, but they are really never the thing.
 
Racerx said:
Always thought of it as the air flowing over the top has to travel farther in the same amount of time.
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Ah, the good ol' "equal transit theory", which many of us learned in school and is complete and utter BS.

Why do the molecules flowing over the top have to get to the trailing edge at the same time as the ones flowing underneath?

Ed Haywood said:
Does anyone other than an aeronautical engineer or test pilot really need to understand lift at the molecular or fluid dynamics level? Probably not. But if you are building an EAB with fabric wings, you better understand there is a pressure differential, lest you skip the rib stitching and wind up with an airport in Oshkosh named after you.
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FWIW, Wittman Regional Airport was so named long before Steve Wittman's fatal crash, but very shortly after he retired after having been its manager for nearly its entire existence.
 
When I was a young student pilot training at KLGB when the tower asked me to “make short approach “ on the downwind leg, I would lower the nose and crank her down in a steep bank without any regard to aerodynamic issues that might arise. My instructor would sit there within his arms folded and never said a word. I understood about keeping the turn coordinated and lowering the nose to maintain airspeed without fully understanding the effects of the aerodynamics at play. If your technique is proper it’s hard to get into trouble, even with limited understanding of aerodynamics.
 
Brad Smith said:
When I was a young student pilot training at KLGB when the tower asked me to “make short approach “ on the downwind leg, I would lower the nose and crank her down in a steep bank without any regard to aerodynamic issues that might arise. My instructor would sit there within his arms folded and never said a word. I understood about keeping the turn coordinated and lowering the nose to maintain airspeed without fully understanding the effects of the aerodynamics at play. If your technique is proper it’s hard to get into trouble, even with limited understanding of aerodynamics.
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That sounds like the old "descending turn" fallacy where the pilot thinks that the load factor is less in a descent. It's not, unless it's a VERY steep descent. Climbing or descending at a steady rate of climb (or descent) is at 1G, just like level flight. Cranking in a steep bank at pattern speeds, even coordinated, is a death wish.
 
Dan Thomas said:
That sounds like the old "descending turn" fallacy where the pilot thinks that the load factor is less in a descent. It's not, unless it's a VERY steep descent. Climbing or descending at a steady rate of climb (or descent) is at 1G, just like level flight. Cranking in a steep bank at pattern speeds, even coordinated, is a death wish.
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Yet another scenario where some indicator of AOA would be valuable, even if for nothing more than a training exercise.

Nauga,
who can see what some people only think they can feel
 
I am not a flight instructor yet, and sorry for being a little slow on the uptake. I just wanted to offer an observation.

TDGlider said:
Sometimes, the most difficult student question to answer is "why do I need to learn this"? One of the topics where I struggle to answer this question is aerodynamics. Why do pilots need to understand how a wing creates lift according to Bernoulli or Newton? Many of us learned an explanation of lift based on the equal transit time theory, which is demonstrably false. Yet, we have been able to control our airplanes fine. I was also taught an incorrect explanation of why airplanes with dihedral have lateral stability. Even though I believed this incorrect explanation for years, I had no trouble keeping the wings level. If one can function well as a pilot despite an incorrect understanding of a topic, that calls into question whether understanding the topic is actually important. So, what do instructors on this forum say when asked by students why they need to learn about aerodynamics.

I am not suggesting that we take this material out of the curriculum (except the parts that are false) I would just like to be able to give a better answer to the "why do I have to learn this?" question than "it is on the test".
Click to expand...


There are two types of students, as I think we can all agree: those that seek the cushy, well-paid airline job, and those that love aviation. Obviously, those that have a passion for aviation can still seek out the airlines, no hate there. But generally speaking, I think students can be sorted into those two boxes.
A student that loves flight will want to know more answers, and will rarely, if ever, ask "why" to learning aerodynamics. The students that ask "why" are only interested in passing the test to keep climbing the ladder. So saying "its on the test" is exactly what they need to hear, and pretty much the only thing you can do.
 
Dilly said:
A student that loves flight will want to know more answers, and will rarely, if ever, ask "why" to learning aerodynamics. The students that ask "why" are only interested in passing the test to keep climbing the ladder. So saying "its on the test" is exactly what they need to hear, and pretty much the only thing you can do.
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This.
 
Ed Haywood said:
I've always felt the stick makes a pretty good AoA indicator.
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My Glasair doesn’t even have a stall warning device let alone AoA. The stick gives ample warning to impending stall. Now, if someone is task saturated or panicking, nothing can help that. Not even an AoA indicator.
 
billsgs126 said:
IDK what type, but it looks like a 2G turn more or less.
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Right around 4g, so about 100% more, more or less. The nose is also trending downward as I'm trying to maintain airspeed as g increases (AKA a 'windup turn'). There's no way to discern AOA from the horizon unless there are other constraints, like wings-level unaccelerated flight, which is far from the case in my pic or @Dana 's

Ed Haywood said:
I've always felt the stick makes a pretty good AoA indicator.
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I agree, to some extent. What's your stick position for on-speed approach? What about best range? ;)

Nauga,
with the needle at 3 o'clock
 
nauga said:
I agree, to some extent. What's your stick position for on-speed approach? What about best range? ;)
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That's why I said "pretty good" and not "perfect." I agree with your original statement about AoA indicators being helpful, and one of these days I'm going to pay attention to the one in my plane and see how it actually correlates to my stick. It will probably be a useful training experience.
 
Ed Haywood said:
...one of these days I'm going to pay attention to the one in my plane and see how it actually correlates to my stick. It will probably be a useful training experience.
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It would definitely be useful, to me if no one else :)

Definitely consider other variables. I don't know the CG travel on a Decathlon but on some airplanes CG position can have a sorta-large effect on stick position relative to AOA. CG also affects AOA for any given airspeed but to a much smaller extent.

Nauga,
and his apparent static longitudinal stability plot group
 
billsgs126 said:
Or the horizon.
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Only in level flight (maintaining altitude and wings level) and a whole bunch of other variables fixed to make it work.

Kind of like when a physicist models a cow as a sphere. On a frictionless surface in a vacuum, of course.
 
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