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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 ...
GdD's user avatar
  • 54.1k
17 votes
Accepted

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 ...
Peter Kämpf's user avatar
15 votes
Accepted

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: ...
Peter Kämpf's user avatar
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 ...
AEhere supports Monica's user avatar
8 votes
Accepted

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^...
mezzanaccio's user avatar
  • 1,739
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 ...
TomMcW's user avatar
  • 28.6k
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 ...
Peter Kämpf's user avatar
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 ...
costrom's user avatar
  • 278
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 ...
Camille Goudeseune's user avatar
6 votes
Accepted

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 ...
Peter Kämpf's user avatar
5 votes
Accepted

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: ...
Peter Kämpf's user avatar
5 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"....
Peter Kämpf's user avatar
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 ...
Peter Kämpf's user avatar
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 ...
rul30's user avatar
  • 1,547
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 ...
Michael Teter's user avatar
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 ...
John K's user avatar
  • 132k
5 votes

How is blended winglet better?

The blended winglet has two advantages: The smooth change of contours means that pressure gradients also are smooth and the flow remains attached through the operating range. The sharp corner of a ...
Peter Kämpf's user avatar
5 votes

Will two counter rotating vortices cancel each other?

Obviously having two perfectly identical and opposite vortices generated in exactly the same space is just an ideal mathematical exercise. I suppose it would something like having two billiard balls ...
sophit's user avatar
  • 14.1k
5 votes
Accepted

Is wake turbulence dangerous to planes of the same size?

Yes, wake turbulence can be dangerous to planes of equal size. Not so much at cruise stage, but during takeoff and landing, yes. The reason for takeoff, initial climb and landing phase being ...
Jpe61's user avatar
  • 29.3k
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 ...
Robert DiGiovanni's user avatar
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: ...
Chris's user avatar
  • 355
4 votes

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

The wingtip vortices carry some energy, and not leaving it behind seems like a good idea. That's why winglets are a thing, after all. So, what if you put a propeller at the wingtip, aligning the axis ...
Zak's user avatar
  • 792
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 ...
S.Serpooshan's user avatar
4 votes

How can I calculate effective wingspan of a high aspect ratio model airplane?

I think the term "effective wingspan" should better be replaced by "effective aspect ratio". There is no change in wingspan when the wing flies closer to the ground, but it behaves like an equivalent ...
Peter Kämpf's user avatar
4 votes
Accepted

How does the adiabatic cooling of wingtip vortices work?

The vortex is rotating. This by itself should suffice to explain the expansion at its core. The mechanism is less Bernoulli (which applies to straight flows) but centrifugal force. Compare it to the ...
Peter Kämpf's user avatar
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 ...
kevin's user avatar
  • 39.8k
4 votes

How can the 777X's longer wing reduce vortices?

So it can fit into standard size airport gates and taxiways. One reason the A380 didn't see wider adoption was it exceeded the maximum wingspan that most airports are set up for, requiring airports ...
tj1000's user avatar
  • 8,787
4 votes

Can wingtip vortices formed around an unswept wing produce vortex lift?

Vortex at straight wing has very small contact area with wing and also at wrong position. Vortex has low pressure, you can see blue color on upper surface where vortex touch surface. This part of ...
22flower's user avatar
  • 1,958
4 votes

Airliner sharp wing tip vs elleptical

Airliners have some boundary conditions which make elliptical wings less preferable. Wing sweep. A swept, elliptical wing suffers lift loss at its center and will easily see its tips stall first at ...
Peter Kämpf's user avatar
4 votes

How do tip vortices make downwash?

Your understanding is sophisticated enough that you shouldn't be trying to learn more from websites and other resources intended for pilots and laypersons. These resources do not apply sufficient ...
Rob McDonald's user avatar
  • 14.3k

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