induced drag explanation

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Working on lesson plans. How would you explain induced drag to a student? All of the explanations in the various texts don't really make it very clear, so I'm looking for something a little easier to wrap your head around.

Thanks in advance!
 
its very complicated when you get into detail... relate it to angle of attack which is the relative wind compared to the chord line of course. well with induced drag you are taking the net relative wind from when it enters the wing and leaves the wing. lift acts perpendicular. that is why when in ground effect the angle is less due to the relative wind leaving the wing being more horizontal. also it decreases exponentially with airspeed: opposite of parasite drag. Like I said it can be complicated especially with pictures. pictures are worth 1000 words.

aoa-effect-induced-drag.gif
 
Whenver I teach, I try to relate the new topic to something any average person can understand. Then I go into details.

For example I've always said induced drag can be related to a midget and tall person running a race. The midget will encounter less drag because they are short (lower AOA) vs the tall person, more drag, (higher AOA)

I know it may sound a little weird but seriously it's worked for all my students and even helped clarify those that were confused.
 
Instructor: If you stick your arm out the window of your car and increase the AOA, what does your arm tend to do?
Student: It moves up
Instructor: Does it move straight up?
Student: No it moves up and backward...(light bulb turns on)...Ohhh!
 
Oldschool Pilot said:
I know it may sound a little weird but seriously it's worked for all my students and even helped clarify those that were confused.
Click to expand...

Except that it isn't remotely correct. A student's ability to understand an explanation isn't a measure of the quality of explanation.
 
Oldschool Pilot said:
For example I've always said induced drag can be related to a midget and tall person running a race. The midget will encounter less drag because they are short (lower AOA) vs the tall person, more drag, (higher AOA)
Click to expand...

Assuming that the midget and the tall person are running at the same speed, the midget will encounter less drag because, unless the midget is very fat, the midget's body has less surface area than the tall person. This example has nothing to do with AOA.
 
whiskeycharlie said:
Instructor: If you stick your arm out the window of your car and increase the AOA, what does your arm tend to do?
Student: It moves up
Instructor: Does it move straight up?
Student: No it moves up and backward...(light bulb turns on)...Ohhh!
Click to expand...
:tmyk: I'm a fan of that one...might have to use it!
 
Oldschool Pilot said:
Whenver I teach, I try to relate the new topic to something any average person can understand. Then I go into details.

For example I've always said induced drag can be related to a midget and tall person running a race. The midget will encounter less drag because they are short (lower AOA) vs the tall person, more drag, (higher AOA)

I know it may sound a little weird but seriously it's worked for all my students and even helped clarify those that were confused.
Click to expand...
I usually avoid criticizing another instructor's methods, but this is simply incorrect. All this shows is the effect of frontal area on parasitic drag. I would recommend clarifying this with them immediately.


I've used the hand out the window one before. It's also great for showing how AOA affects lift. Physical examples that the student can see and feel usually work better than concepts being drawn out on a whiteboard.
 
whiskeycharlie said:
Instructor: If you stick your arm out the window of your car and increase the AOA, what does your arm tend to do?
Student: It moves up
Instructor: Does it move straight up?
Student: No it moves up and backward...(light bulb turns on)...Ohhh!
Click to expand...

Yep, this is how I've always thought of it myself. Much simpler than talking about "induced angle of attack" and "bending the lift vector backwards". If I was the student and I heard something like that, I would have run for the door. I guess I'm also concerned about this coming up during the checkride (oral). Whenever I imagine myself trying to explain this to the examiner, I feel like I'm speaking another language and he's looking at me like I'm an idiot. Haha. Thanks for the ideas.

And the midget idea may get a laugh but would probably be better for explaining form drag?
 
DaveC said:
I usually avoid criticizing another instructor's methods, but this is simply incorrect. All this shows is the effect of frontal area on parasitic drag. I would recommend clarifying this with them immediately.

I've used the hand out the window one before. It's also great for showing how AOA affects lift. Physical examples that the student can see and feel usually work better than concepts being drawn out on a whiteboard.
Click to expand...

Good call and my mistake, thanks for correcting me. I have used the hand idea myself but more so taught that showing how a wing creates lift.
 
indeed, that was parasit/form drag with the midgets. I'd say start easy and then get technical if you are a cfi. also profpilot...haha great job. Hey if a robot can do it, you can too
 
I like the explanation on Aerodynamics for naval aviators (H. Hurt), which is kinda similar to what is posted on the 2nd post. Its complicated, but heck, you just need to have an idea of "why" it exists, but thats not the most imporart part about understanding induced drag.
 
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