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Shape changing

Shape changing

Would a wing that could change it's shape in flight have any advantage over other wings? e.g. go from deep chamber to low chamber...

RE: Shape changing

 In the 1950s Gus Raspet at Mississippi state university
Fabricated an all fiberglass aircraft with a camber changing wing.
 In the 1980s I helped take that wing off and install a conventional wing with flaps.
 That aircraft is now in the flight museum in Birmingham Alabama.
 Here is a press release from the aircraft dept at Mississippi state.

 The university may have performance details of the old airfoil in their archives.

RE: Shape changing

Thank you Berkshire. That is exactly the information I was looking for.

RE: Shape changing

wasn't there a more recent research project with an F111 fitted with a variable camber wing ? ... instead of discree flaps and slats, there was an single cover whihc could deflect the L/E and T/E.

RE: Shape changing

Birds do it ---
Bees do it ----

Maybe we cold learn a thing or two ---

RE: Shape changing

Geez, Mike, always taking things into the gutter...;)

RE: Shape changing

I want to thank everyone for their knowledge and advice.
You people "engineers" really amaze me. Most of you could figigure out how to get blood from a turnip the other half could\would get more blood from a smaller turnip.

The reason for my question isn't airplane design\construction. But more layman's understanding of wings,airflow and lift.

So, whith that said, let me delv a little more into my project.

"Forget about size and weight for a moment".
As I understand it a plane/wing with a deep chamber needs less air speed and runway to take-off "Glider compared to fighter jet"?
If a plane has a shallow chamber it wil use less fuel to climb "Kinda like a bullet shot straight up"?

Is this a correct assumptions? If so then a fly by wire control of the wing shape along with flaps would give the best of both worlds, would it not "Yes wing shape and flaps for precise control"?

My current computer model gives me a 35% savings in fuel if what I stated is correct.

RE: Shape changing


I'd like to comment one little difference that might be overlooked here on the flaps.

If you form flaps by means of a kneadable geometry the result is not the same as a "real" mechanical flap. In case of a normal flap there's an open space to re-energise the boundary layer on the suction side with air coming from the pressure side. (In fact normal flaps can be considered a variable geometry as well).

Your question made me think about another question...   ...what's more effective for the airfoil's glide ratio, a bit of camber increase or an increment in the angle of attack? I never checked that...   If angle of attack is the answer, cambering your wing is an expensive solution to vary the aerodynamic properties. It all depends on your design angle of attack and your take off and landing boundary conditions I think.

I think that the speed range that you need will give you the answer whether it's worthwhile to build a kneadable geometry. The F-14 and the swift (I mean the bird,not any airplane type) are extreme cases, but for normal applications it's not necessary to overcomplicate life a s the swift does.

BTW3: (lots of BTW's BTW)
Fly by wire has only been invented because of the extreme  dirigibility that seemed necesssary in fighter aircraft. For commercial aircraft, at least as far as I know, it's not necessary at all to fly stable.


RE: Shape changing

FbW ... military planes use it to fly unstable airplanes; commerical planes use it mainly (i think) for advantages of digital data (commercial planes are stable).  comercial planes were interested in "gust alleviation", a FbW system can react quicker than a pilot and smooth out the effects of gusts, initialy people thought this would improve the fatigue life of the wing (and maybe the comfort of the pax); fatigue life actually dropped, 'cause the wing wasn't seeing beneficial overloads ... reality bites.

camber ... planes use camber (L/E slats and T/E flaps) on take-off (and landing) to increase CL, reduce ground speed of the plane.  previous post is right about the effects of the open slot (to reenergise the boundary layer).

i just googled "F111 variable camber" and came across the project i thought about at first.  called "mission adaptive wing", NASA Langley did some research with an F111 lifted with a smooth upper surface (instead of discrete flaps).  judging by the lack of follow up, maybe it isn't worth it.

RE: Shape changing

FbW's main advantages and uses are:
>  Ability to use "command" the flight computer to make a manuever and have it provide the necessary high-speed commands to compensate for aircraft instability
>  Elimination of a considerable amount of mechanical weight, since the mechanical linkages need redundancy, hydraulics, supports, reinforcement, etc.


FAQ731-376: Forum Policies

RE: Shape changing

Following up on the variable camber wing.
The reason the wing was removed from the aircraft at Miss state was, that although you could increase the CL of the wing, you could not increase the area of the wing.
 The flapped wing fitted, had offset hinges that allowed the area of the wing to increase as the flaps were deployed.

RE: Shape changing

The other thing that I don't think has explicitly come up is that wing design is almost always a compromise.  Be it a compromise between aerodynamic performance, structural mass, ease or manufacture or between performance at different points in the flight profile.

There are a lot of interesting concepts that have even been tried out at large scale but typically don't go far because of the mass penalty. I thought the MAW was one of them, suction on wing surfaces to reduce drag was I thought another.

Posting guidelines FAQ731-376: Forum Policies (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: Shape changing

Personally, I don't think so. It could only have an advantage if the flight conditions have to be changed radically. Like from extremely slow to extremely fast for example, but for one normal cruise condition? I don't see why there should be an advantage. Especially because it's very hard to manufacture such a thing and thus very expensive.

One may also think of using variable geometries to enhance the maneuverability of a plane (birds do that).

In fact the flaps and slats that are being used during landing and take off are variable geometries as well.

I can also imagine a drag reduction for supersonic airplanes, because after all they have to take off subsonic. Maybe the moving nose of the Concorde is an example of something like this, but I'm not sure whether drag reduction was the goal there, I don't know, but it's what I suspect. Maybe someone can confirm that.  

RE: Shape changing

i understood the concode's moving nose was for ground visibility due to the high AoA on landing.

boundary layer suction, from Keant's last post, is another way to improve a wing's performance at the cost of weight, engine power; it did a good job on the Buccanneer, so it probably fits in special applications but not generally.

any thoughts newton ??  anything helpful ??

RE: Shape changing

Hey, sorry for my strange "answer" I was on another forum at the same time and thought the posts were going up chronologically in stead of down. Anyway, BL suction is extremely energy consuming, I suppose it's only interesting for military porposes. I'd never use it to reduce drag, because what you win on drag reduction is probably being spent on the suction of the BL.

RE: Shape changing

rb1957, I believe the Buccanneer actually used boundary blowing not suction.

Concordes nose was for visibility, though arguably it was also to reduce drag as a more conventional stepped nose configuration to give visibility would have had more drag.

Posting guidelines FAQ731-376: Forum Policies (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: Shape changing

This will label me a geek... but I think the best example of what you're talking about is shown in the anime movie Macross Plus where they have an airplane that changes the configuration of it's wing thru nanotechnology, sweep, chord and geometry are all infinitely adjustable by the pilot. This may one day be a possibility, but for now there is not much you can do to gain this ability without sacrificing weight or huge amounts of money.

You must always design a wing to be best at what it's role will be, and the tradeoffs you get from such extreme wings can significanly affect the handling of the airplane in all other flight envelopes. Two examples:

The U-2, a wing that gives so much lift that the airplane can't land unless it's fully stalled.

The F-104, a wing made so fully dedicated to speed that blown flaps were needed to get landing speed slow enough to make landing at all possible. The F-104 killed a great many pilots because of this wing.

So yes, a variable geometry wing can be made, but the cost will always outweigh the benefits.

RE: Shape changing

I know there have also been some tests with the RQ-7 Shadow UAV.  The wing houses fuel bladers that define the max size of the wing.

When the plane takes off the plane has a thick airfoil cross section, but as fuel is consumed the foil thins out as the bladders empty.  The wing surface settles down onto a frame defining the minimum thickness profile.

This alows the plane to carry more fuel than a thin wing section would alow, and provides added speed and efficiency as the reservoir empties.  It also seems like it is not to costly to impliment, although the wing shape is not constantly varied to increase performance as some of the things mentioned above.

RE: Shape changing

Here is what I was refering to.  Looks like it is research, not testing as I said and it isnt specific to the RQ-7, just general UAV optimization.

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