17 votes

What are some drawbacks to having a wingtip propeller on an aircraft?

Feathering isn't really an issue, if you can feather a prop on an engine further inboard you can do it on the tip too. There are 3 major drawbacks that come to mind: The wing structure has to be ...
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15 votes
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Why are vortices produced at wingtips a source of drag, while vortices from the leading edge (harnessed by delta wings) good?

You ask the right question. Given the amount of misinformation out there, I can understand why you are confused. First the tip vortices: They are neither a source of downward force not do they cause ...
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14 votes
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How do Hoerner Wingtips work?

How exactly does acceleration of air occur just by having a convex underside Just like the curved forward surface of a wing does it. Imagine for a moment that the air flows along a straight path: ...
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11 votes
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Why does the vortex created by wing affects its own angle of attack?

The wingtip vortices create both upwash and downwash; The downwash lies within the wingspan and affects the wing angle of attack while the upwash region lies outside the wingspan and can be utilized ...
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10 votes
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How "powerful" is a wing tip vortex?

If we're talking about large aircraft the answer is Powerful enough that you want to stay out of them. I refer you to this delightful FAA video in which a Cessna (looks like a 172) was flown into the ...
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  • 67.2k
10 votes

Can wing-tip vortices be reduced/eliminated with a rear-facing propeller near the wing-tip?

Yes. From an aerodynamic standpoint it makes some sense to use the wingtip vortex in combination with a propeller. In this article by Sinnige et al., the researchers modeled and tested a propeller in ...
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9 votes

Why do wing tip vortices tend to be most dangerous when there is a light quartering tailwind?

The wing tip vortices cause significant problems for (small) aircraft taking off after a large aircraft. the FAA Advisory circular 90-23G deals with this. As an aircraft takes off, the the vortices ...
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9 votes
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Why do wing tip vortices tend to be most dangerous when there is a light quartering tailwind?

According to the FAA's Pilot and Air Traffic Controller Guide to Wake Turbulence (section 2.4.5) it's because: Light: in light winds the vortices stay around longer; if the wind is greater than 5 ...
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  • 70.2k
8 votes

Is induced drag caused because of the tilt of the wing backwards?

Although your explanation isn't entirely wrong, It isn't necessarily the backward tilt of the wing, but the backward tilt of the aerodynamic force. I look at it from two different perspectives. The ...
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  • 27.5k
8 votes
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Why does a clean configuration lead to the generation of greater wingtip vortices?

I would actually assume the opposite to be true. Let us assume the vortex intensity and the induced drag are directly correlated. The induced drag coefficient can be expressed as: $c_{Di}=\frac{c_L^...
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  • 1,679
6 votes

Why is a wing tip's front edge tapered?

The swept-back wingtip has been successfully employed by water fowl for many millennia. The use of composite structures has made the three-dimensional shaping of wingtips much easier, and the first ...
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6 votes

How "powerful" is a wing tip vortex?

Depending on the size of the aircraft, very powerful. One way of thinking about his would be that the velocities in the wake are directly related to the lift produced. So, heavier the aircraft, larger ...
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  • 98.3k
6 votes

Can wing-tip vortices be reduced/eliminated with a rear-facing propeller near the wing-tip?

Eliminate, no. The wingtip vortices are inherent part of lift generation. There is no lift without wingtip vortices. The wake vortices are carrying the momentum that was given to the air to produce ...
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  • 54.1k
6 votes

Can an aircraft or helicopter run into its own wake vortex?

I've certainly run into my own wake turbulence when doing steep turns in a Cessna 172. In fact, it's the mark of a well-executed 360 degree steep turn that you do feel the bump of running over your ...
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  • 3,608
6 votes
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Can an aircraft or helicopter run into its own wake vortex?

Helicopters are not easy to fly - whether full-scale manned aircraft or RC models. I would bet that your issues are more related to pilot error than any fault of the machine (other than the fact that ...
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  • 67.2k
6 votes

What are some drawbacks to having a wingtip propeller on an aircraft?

Another non-flying attribute that having a wingtip-mounted propeller can drive is landing gear length. Since there are minimum clearance distances for propeller tip to ground during taxiing, and the ...
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  • 269
6 votes

Are there advantages to slotted wingtips?

Slotted wingtips provide torsional flexibility. A bird’s wingtip feathers must twist in one direction during the upstroke of the wings and in the other direction during the downstroke to keep the ...
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5 votes
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Do vertical stabilizers create vortices like wingtips do?

In general, the vertical stabilizer and rudder create a symmetric airfoil. As there is no pressure difference between the two surfaces of the vertical stabilizer, vortices doesn't form, unlike the ...
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  • 98.3k
5 votes

Design winglets to counteract tip vortex

Please stop following the cult of the wingtip vortex and start to gain a better understanding of the flow around a wing. Stop reading if you encounter any of those myths: Pressure differences at the ...
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5 votes

How do wing tip vortices interact with the airflow on an wing with winglets?

Winglets do not change the laws of physics. In particular, they do not change the flow around a wing such that there is no up- or downwash. All they do is to involve a little more air into the ...
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5 votes

Do wingtip vortices really only form when airplane wheels are separated from the ground?

You are absolutely right. The vortices form whenever the wings produce lift. Even if the lift is not enough to let the aircraft fly. Of course it is necessary to have a flow across the wing, and with ...
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  • 1,537
5 votes
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Spanwise flow and wingtip vortices in forward-swept wings

There is no magical switch that gets flipped once you cross a specific sweep angle. Things are gradually changing with the cosine of the local sweep angle. Now let's look at your questions one by one: ...
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5 votes

What are some drawbacks to having a wingtip propeller on an aircraft?

Moving the thrust (and additional weight) to the wingtips creates more drawbacks than benefits. Yaw - because of the increased moment of inertia (compared to having the engines be closer to the ...
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5 votes

Are there advantages to slotted wingtips?

They function like an array of winglets. Each feather is aligned to optimize its angle of attack in the local flow, which is circulating from the bottom to the top around the tip, to extract energy ...
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  • 103k
5 votes
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How can one change the wingtip geometry to enhance the wingtip vortices?

You are not interested in wingtip vortices. For now you are barking up the wrong tree. For that tug idea to work, you need to focus on the trailing vortex which is a result of the whole wing, not the ...
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4 votes

What is the best combination of airfoil shape for flight in ground effect over water?

There are three considerations for this design: Airfoil shape Aspect ratio Dihedral/Anhedral Airfoil shape: high lift undercambered thick and very forgiving - good idea near the ground ...
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4 votes

Why does the vortex created by wing affects its own angle of attack?

Near the wing the bound circulation due to lift leads to an up-wash ahead of the wing and downwash behind the wing similar to the flow produced by a two-dimensional lifting wing of infinite span. A ...
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4 votes

Can wing-tip vortices be reduced/eliminated with a rear-facing propeller near the wing-tip?

Doug MacLean has a great synopsis of wingtip devices that is worth reading, and gives a good intuition as to why propellers could reduce, but likely not eliminate, the wingtip vortex. To summarize: ...
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  • 285
4 votes

How and why do wake vortices come together to form two tip vortices?

The picture in your question is an oversimplification. Maybe this photo of an MD-11 on a moist day will help to illustrate the point: I also think you should not call the wake vortices "tip vortices"....
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4 votes

Do wingtip vortices really only form when airplane wheels are separated from the ground?

You are correct, but your textbook is more correct. Here's why: Your reasoning is that lift is a function of airspeed, which is true. However lift is also a function of angle of attack. This is why ...
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