# Tag Info

## New answers tagged aircraft-design

0

I'm a vibrations guys (although not specifically wing vibration), so let me add one point to complete niels nielsen's answer. If the mass of the wings is reduced by removing the fuel, but the stiffness of the wings stays the same, then the natural frequencies of the wing will go up. A higher natural frequency would have an effect on flutter margin (probably ...

3

This has been well-studied, here are the basics. For the case of fuselage tankage for fuel: The structural loads caused by the weight of the fuel in a fuselage tank must be transmitted between the wings and the fuselage. This means beefing up the wing-to-fuselage attachment points, which is not required if the wings carry the tankage instead. Putting the ...

1

The main reason is the Reynolds number and the way it affects the airflow. The stalling angle is more or less constant for all airfoils over a range of speeds. The shape and airspeed of the airfoil in themselves make very little difference to the stall angle. The stalling speed of a plane is dictated mainly by the angle of attack required to provide adequate ...

1

I will try to make it simple without going into mathematical details. Source Here, λ = ctip/croot The important factors controlling the lift in the Tapered wing. The ctip being too small affects the Reynolds Number (as the distance travelled is very small). Assuming the constant speed, density and viscosity, Reynolds number only varies with the distance ...

0

Spanwise flow seems to have a lot to do with it, and the wingtip vortices can affect both the local effective Angle of Attack and the airflow of the upper wing. (Credit to @Noorul Quamar) Let's start with the rectangular wing. It stalls at the root first. Maximum pressure differential between upper and lower wing, and interference of the fuselage (and prop) ...

5

Plain and simple, to meet current market requirements, Airbus can do pretty much nothing to make the 380 more "current". The technical improvements suggested do nothing to change the fact that the 380 is too big, that is, it has too many seats, thus not allowing enough flexibility in this market situation. In addition to not addressing the main ...

1

The underlying assumption of your question seems to be that a higher control bandwidth always leads to better disturbance suppression. Since a higher control bandwidth is easier to achieve with low-inertia systems, aircraft with low inertia would have better disturbance suppression. This assumption can work in theory, especially for SISO (single-input, ...

6

As you've already learned from the comments, the hard part of getting to space isn't the height, it's the speed. The Saturn V broke the sound barrier less than 30 seconds after launch. So, how is your refueling plane even going to keep up? The only possible answer, at least with modern technology, is to make it a rocket itself. So, now you've got two rockets ...

0

We draw the connection by noting that lift is a force, and that force is pressure/area $L/S = 1/2 * r * v^2 * CL$ L/S is the average pressure difference between the top and bottom of the wing! Now, we rearrange your equation to make a fixed pressure - or rather in this case, a pressure difference - the subject. P2 - P1 = (1/2 * r * v2^2) - (1/2 * r * v1^2) = ...

4

Well, it's the same reason that the Challenger ultralight demonstrates extreme "adverse yaw" in response to aileron inputs when flown with the doors on, but less so when flow with the doors off. The floats-- like the doors-- increase the surface area in front of the CG, which has an effect similar to decreasing the size of the vertical fin (which, ...

3

The Cessna 172S has more power (180hp vs 160hp for 172R) and higher MTOW (2550lb vs 2400lb for 172R). This means that folks used to rotating at 55 knots IAS in earlier models would be closer to stall if taking off "clean". Another way of doing it would be to add 5 knots and rotate clean at 60 knots. Vx is also a bit higher in the 172S at 62 knots ...

1

The typical shape as pointed out in the question, a diverging nozzle, is for "pressure recovery". For engine efficiency or combustion efficiency, higher static pressure is required. The shape is selected to convert the dynamic pressure (pressure due to velocity) to static pressure, which improves the engine performance. The opposite shape would be ...

4

It's simply a NACA duct inlet. On a fully parallel to flow flush surface it has some (but not all) of the effectiveness of a protruding scoop, without the drag. The curved sides of the ramp act like vortex generators, with the rotation of the vortices on each side pulling air down into the ramp. On a very clean airplane like one of the RV series homebuilts,...

2

The operative term to look up here is ground pressure. This is simply the force required to support the object divided by the area that force is spread over. You can reduce the ground pressure of an aircraft by increasing the size of the landing gear - most obviously, using more wheels and/or larger wheels. On low-friction terrain (ice, snow), try skis - ...

0

Of course, carbon-based propellants are unacceptable today, while other heavy gases are either pollutants too, or scarce and expensive (a tankful of xenon anybody?). A metal hydride can store a surprising quantity of gas, but hydrogen is too light to exert thrust efficiently. Compressed air is about your best bet. Frenchman Victor Tatin flew a 1.9 m (6 ft 3 ...

5

The problem with the MAX has nothing to do with the elevators being ineffective, the characteristics which lead to the pitching up will be present wherever you put the tail. It's the placement of the engines that are the problem. Moving the tail would require big changes, you have to strengthen the tail and structure around it, which would be extremely ...

9

No. A t-tail would worsen the characteristics of the airplane. While not necessarily a horrible idea in its own right, the already-nasty slow-flight/high alpha/stall characteristics of the aircraft that necessitated MCAS in the first place would make this idea dangerous. The pitch-up tendency could lead to a stall, which in a T-tail can lead to a deep stall. ...

0

To elaborate a bit on Robert DiGiovannis answer, yes certainly that would increase the range, if not for any other reason, than because it is quite easy to make it add considerably to the structural integrity of the drone. Another thing you need to realize is, that saving weight and other range extending measures can come in a lot of small contributions, ...

0

One way of looking at this (thanks to fine data chart by Pilothead) is wing loading, and it is best based on takeoff weight, speed, and anticipated G loading in manuevers. Going to the formula Total Drag = CDo + CDi, we can see why many designers pursued flying wings: theoretically, almost all drag is CDi (induced drag). Looking at the high lift to drag ...

0

Ultimately, the history of the debate was all about engine power and speed. In the early days engines were pretty pathetic, forcing designers down the braced-wing route, so aerofoils could be made thin with all the stiffness conferred by the bracing. The thick vs. thin debate over monoplane wings first took reasonably informed shape in the latter part of WWI,...

4

Wing structure is roughly 20% of empty weight, which is roughly half of gross weight. I clipped the two sources some time ago and no longer have references.

10

Truly leading edge ailerons would not work. It is mainly the orientation of the trailing edge that determines the direction in which the air flow continues behind the wing and therefore the lift. The forward part of the wing is there mainly to turn the air flow gently so it stays attached to the surface. If you have a leading edge flap, and deflect it ...

1

Simply put, the weight of such a system alone is enough to make it not feasible. Rescue chutes work satisfactorily on smaller planes as they are, not surprisingly, quite light. For a passenger plane, the parachute should be (at least) an order of magnitude bigger i relation to plane size. This is because if you double the mass, you quadruple the forces ...

1

Simply put, planes are designed to not crash. Anything kind of safety measure you add to a plane will come with some opportunity cost - instead of that particular safety measure, you could have spent that money on something else. Overall, it's more cost effective to implement safety measures that prevent the plane from crashing in the first place, rather ...

6

JW Dunne briefly tried leading-edge elevators on the D.3 glider at Blair Atholl in 1908. His aircraft had tailless swept wings. The elevator flaps were triangular shaped and fitted at the nose. They just blew back over the wing in flight, and he gave up on the idea. (The first certified stable aeroplane, the D.5, was of similar design and flew in 1910, and ...

6

I have seen photos of a hang glider that was modified to have spoilers (or "spoilerons")1 on the top surface of the wing for better roll response. The spoilers were controlled by sliders on the control bar, and both could be opened at once for extra drag to increase the descent rate. The spoilers were hinged at their leading edges, like typical ...

15

They were tested in 1935. Since ailerons are thin (thickness-to-chord ratio), they were placed in a leading edge slot, and it was dubbed slot-lip aileron. The study's conclusion is: The slot-lip ailerons appear to be usable as a form of lateral control device that shows promise of giving improved lateral control and stability at the high angles of attack ...

1

b) is a correct description of both . "Spanwise" is perpendicular to the aircraft's longitudinal axis because it does not relate to the width of the wings, but to the span of the aircraft. which includes both the wings and the fuselage. Consider that the wings of most aircraft and all birds, don't really have a clear "root" where the ...

4

There are technical limitations. When I fly a two-seater, my thermalling technique is different from flying 15m single seaters. With the single seater it is no problem to center the thermal while observing the variations in climb speed. Tighten the turn when climb speed drops and vice versa. But with two-seaters I wait for a three quarter turn and only then ...

1

Yes. The location of the chines occupy the same fuselage station coordinates on both single and dual seat versions of the F-16. The addition of a second crew members station in the aircraft necessitates the removal of a forward fuel tank, reducing the total internal fuel capacity of two seat F-16s.

3

In airplane empennage design, there is a thing called Tail Volume Coefficient. Mind you, there are no volumes here, but you are working with $m^3/m^3$. It is calculated as follows: Horizontal tail volume: $V_{HT} = \cfrac{ l_{HT} \cdot S_{HT} }{ c_{REF} \cdot S_{REF} }$ Vertical tail volume: $V_{VT} = \cfrac{ l_{VT} \cdot S_{VT} }{ b_{REF} \cdot S_{REF} }$ ...

5

A key thing you need to provide is the ratio of L/D, which is also equivalent to the ratio of Cl/Cd, where Cl and Cd are the lift and drag coefficients. Thrust required for level flight = D/L ratio * Weight. Without knowing more information, including L/D ratio and Weight, the answer to your question can only be "maybe". If the L/D ratio is 10:1 or ...

0

When building kits I have more than a few times come across the explanation of the seals being for water and element protection. It depends on the installation, on something like a Cherokee it would help reduce drag but be most effective in keeping the wing attachment dry and protected from the element, on a composite it finishes off the smoothed out ...

0

This question is interesting as it delves into the efficiency cross over point between airships and aeroplanes. From history we learn that airships had efficiency advantages up to around 80 knots, but were bulky and hard to control in poor weather. A drone sounds like something that may fly at slower speeds, so why not cut loose a bit and think about a ...

1

The wing root seal reduces drag. In glider aircraft with detachable wings or foldable, the seal is often nothing more than tape.

17

I can't speak to the design criteria, as I wasn't there when the airplane was designed, but I do have time in type and experience flying and maintaining the P2V. There's more going on than just engine, with respect to the nacelle. Remember that the nacelle is partially a fairing for the engine, and serves as the aerodynamic afterbody, but that conical shape ...

26

That shape was adapted after wind-tunnel tests showed the original less-tapered nacelle creating downforce, which meant the rest of the wing had to deal with more upward bending (lift distribution more toward the tips). To solve this problem, the beaver-tail-shaped end was used – reducing the flow separation that caused the downforce. The thrust-axis was ...

4

If the end result of the sealed wing filled with helium is lighter than the same wing filled with a normal atmosphere (nitrogen, oxygen, and assorted other gases), then yes - a lighter aircraft will, all else being equal, have better performance and thus longer range than a heavier one. If you'd actually be able to achieve economic benefit is doubtful - the ...

0

It's not guaranteed that the missile/bomb will stay upright relative to an asymmetrical wing throughout its whole flight, and if it were to wind up inverted, the range would be shorter and the package would fall short of its target. That might mean on civilians or friendly forces, and that's not good. Asymmetrical airfoils are effective, and they get the job ...

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