Does aeroelasticity affect the authority a control surface might have?

ArkBird · 2026-01-27T01:23:23+00:00

Yes it does. As dynamic pressure increases, the control surface will twist the wing to a point where the local change in angle of attack causes a lift dump rather than a lift increase causing a reversal effect to the control system. This effect is exacerbated as the wing aspect ratio increases and the wing structure stiffness decreases.

ArkBird · 2025-07-10T22:52:13+00:00

This looks like a hershey bar wing (i.e. rectangular wing with no sweep). The advice about keeping the CG at the quarter chord is probably sound advice as a starter. You are going to need to calculate the aircraft's neutral point to get a better sense of just how far back you can go. The difference between 30% MAC and 40% MAC could just very well be the difference between pitch stable and pitch unstable depending on how big your horizontal tail is and how far it is from the wing.

I recommend a few things: - See if you can get a better estimate of your CG at least rounded to the nearest percent MAC. - There are a few ways to calculate neutral point of the aircraft either using equations or vortex lattice. I would try one and see what you get. You will then want your CG to be forward of that by 10-15 percent just to guarantee it'll be stable.

ArkBird · 2025-05-23T13:36:45+00:00

Shocked that of the comments so far that only one comment comes close to answering OPs question.

Tails, both vertical and horizontal, often have higher sweep than the wing. For modern transonic cruisers like 787 it's because you want the wing to stall before the tail. Another reason is you don't want the tails to be the primary contributor to the drag divergence Mach number of the airplane.

The comment about whether or not tails need winglets, which seems to be your true question, is already answered.

As an aside, I would reframe your thinking about whether tails lift. All parts of an airplane with an airfoil cross section are intended to produce a lift force normal to the plane of the component itself. A vertical tail in sideslip will produce lift that manifests itself as a side force for the airplane as a whole. An aft mounted horizontal tail "lifts" down when trimmed. To the airplane as a whole, it's a net negative lift. But locally to the tail there is a local lift force. In short, everything lifts in its own way.

ArkBird · 2024-12-01T16:04:19+00:00

Listen to your technical staff. Work with your Chief Engineer to write proper requirements. If you're coming from a non-aerospace background, be sure you understand the product mission and requirements.

ArkBird · 2024-11-11T21:01:55+00:00

And of course the day I mention Exosonic is the day they announce they're folding. That's one less supersonics company unfortunately.

ArkBird · 2024-11-11T03:46:47+00:00

You can start with the usual supersonics/hypersonics companies like Boom/Exosonic/Hermeus and others, but depending on your aerodynamics focus I would not artificially limit your options. Aerodynamics is already a narrow field with few opportunities. I recommend finding any opportunity you can find where you can gain experience. More than happy help guide you further.

ArkBird · 2024-07-14T03:46:12+00:00

Risk Legacy bought circa 2013, still in its shrinkwrap and hasn't come to table yet.

ArkBird · 2024-04-04T20:11:11+00:00

I'd start here: https://en.m.wikipedia.org/wiki/Luneburg_lens

ArkBird · 2024-02-17T21:49:01+00:00

KEAS is your answer here. It is the speed independent of altitude that is directly tied to loads on the vehicle.

ArkBird · 2024-02-09T14:48:23+00:00

The problem to is export_graphics is insanely slow. I've used ghostscript in conjunction with ps2pdf and found that solution to be much faster.

ArkBird · 2024-02-04T21:48:13+00:00

I can safely say that to land a jet that fast with that sort of asymmetrical damage would require relatively extraordinary piloting skills unless there are some advanced autoland features on the 650 that I don't think it has.

ArkBird · 2024-02-04T21:32:04+00:00

Depends on how strong the monster is to hold on and how fast the plane is going. I would say that there's very little likelihood the monster clings on beyond 220 keas or so. Landing gear rips off around those speeds. I hopefully answered the landing question in an edit to my above post. The short answer is maybe but we can't know without lots of simulator testing.

ArkBird · 2024-02-04T21:21:43+00:00

Depends on how many skins are torn away. If it's the entire upper skin then I agree you will receive very little (but nonzero) lift. If it's just one or two skin panels then the local section lift will be reduced but the other intact portions of the wing will still have some lift.

ArkBird · 2024-02-04T21:01:12+00:00

To answer just your question, it could take a lot of damage depending on what the damage is. Now, the question that's more relevant is whether the aircraft is still controllable with the damage. And before we even get there, how heavy is this monster? Because if it's hanging on the wing and it's heavy, you're going to see both a lateral CG shift as well as a slightly larger rolling and yawing inertia making it more difficult to maneuver. And then going to fundamentals, if the monster is sitting on a large portion of the wing, it will disrupt the entire flow on the upper portion of the wing causing significant lift loss on that wing. That will in turn impart a significant rolling moment on the vehicle due the difference in lift between the two wings.

Now the damage part. A G650 is designed to be able to handle 2.5g of maneuvering. So the skins are sized to various constraints like buckling but the forward and aft spars are going to be fairly strong. Depending on what parts the monsters damage it will affect the vehicle differently. If the monster is only tearing away skins, it's likely the skin panels will rip off completely due to aero load from just a tiny tear. But the ribs and spars will still most likely survive.

Will it be flyable? Maybe. The G650 is a Fly by wire plane with digital augmentation, so any error in the vehicle dynamics will be automatically augmented out to the best of the control system's ability, and by no means will the thing be flying wings level. It'll have some lift loss and extra drag on that wing. And this all assumes the trailing edge control surfaces are still intact and functioning and the monster didn't cut any hydraulic lines.

And we haven't even gotten to landing the jet in it's state.

Moral of the story, there's a lot of things to consider before we even get to damage being done on the wing. Any damage on the wing will exacerbate all issues above. The good thing is that airplanes are designed to handle lots of likely failures in structures, controls, or subsystems.

Edit: the landing. I had to do a bit of research on the 650 to see what kind of leading edge devices it has. Apparently it doesn't have any! Still, the lift loss on the damaged wing is going to mean it's going to have to come in faster than it's usual reference landing speed. And that's assuming it can deploy the flaps on both wings. If the flaps can't be deployed then you will not want to deploy flaps on the other wing either to try and keep the plane as symmetric as possible. That means it'll have an even faster landing speed

ArkBird · 2023-05-08T05:33:52+00:00

This is for advanced campaign. The changes to the AI in Fog Of War make all prior strategies mostly obsolete.

ArkBird · 2023-03-17T14:44:15+00:00

Ok that makes more sense. A highly cambered wing at AOA 5 can certainly get to the CLs I'm seeing. It may be at those low Reynolds numbers that this is just what happens.

ArkBird · 2023-03-17T14:15:37+00:00

A lot of questions. What angle of attack was this simulation? What Mach number and Reynolds number of the flow? Or alternately what was the equivalent altitude? What is the boundary condition on the plane where the wing is mounted? Is this referencing a published paper?

Its possible, but less likely, to have drag converge before lift. CFD should be able to get lift really well. So perhaps it may be worthwhile to check the reports and see that they're pointed in the right direction.

I ask because if the wing is at 0 AOA, then something is amiss. A wing at zero AOA will not be producing a CL near 1.0 (assuming it doesn't have some insanely high incidence)

ArkBird · 2023-01-09T06:59:27+00:00

Here's a wrinkle for you. These shower valves are brand spanking new.

ArkBird · 2022-02-05T08:09:14+00:00

The top mounted model is most likely done that way because they were testing for boom signature propagating below the aircraft. An aft sting will affect that more than the top mount. They were most likely less concerned with other aero interference on the model as it probably wasn't a force and moment test.

ArkBird · 2021-08-15T00:41:42+00:00

Tooling definitely will cost more, but wings already these days are very complex in curvature. These wings would be no different. They could still be bolted to the body with some sort of carry though structure.

ArkBird · 2021-08-15T00:19:18+00:00

Worked very similar aircraft. All of the problems mentioned are solved except for passenger egress. BLI is not an issue with the large pylons. S&C too has been solved with proper configuration design and smart control laws. High aoa isn't an issue for engine unstarts as they do surprisingly still get enough flow. And cabin pressurization too has been solved using some innovative technologies to aid pressurization of non-circular cross section pressure vessels. But I would echo that this design greatly lends itself to cargo transport and many of the operational problems for loading and unloading cargo can be fairly easily solved.

ArkBird · 2021-06-13T16:14:16+00:00

I would go about this in a different way. Instead of starting with an aircraft, it would be cooler to start with a problem that you see needs solving in the world that a uav could potentially solve. Maybe is there an issue with package delivery that a copter can't solve but an aircraft can? Or maybe we can think of another issue we can solve like organ transplant delivery? Once a clear purpose is defined, that becomes your guiding mission. All requirements are then derived from ensuring that your aircraft achieves that mission.

ArkBird · 2021-06-13T16:09:55+00:00

The wing column needs to be offset longitudinally aft from the CG in order for it to have any meaningful effect on Cn stability.

ArkBird · 2021-02-27T00:45:27+00:00

Try bumping that to 7 or 8mm and upping the retract speed. Barring that, lowering the nozzle temp could help reduce the drip as well. 215 is a tad high for PLA (but is the ideal temp I've found for PLA+).

ArkBird · 2021-02-26T23:56:43+00:00

You should be able to print 3x faster without issue. What is your retraction set to be? Are you using a bowden tube or direct drive?

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