New answers tagged

1

There is theory, and then there is real life. The advantages (for general aviation) of modern airfoils fall mostly in the former category. This paper on airfoil selection explains this much better than I ever could. My designs (full disclosure: these exist only on paper up to now) tend to get a "catalogue" airfoil, because the properties and ...


3

The flaperons' deflection when used als trailing edge flaps is controlled based on the landing gear handle position, the ALT FLAPS switch position, the airspeed and the mach number, but is independent of whether the aircraft is airborne or on the ground. When the landing gear handle is placed in the DN (down) position or the ALT FLAPS switch is placed in the ...


4

Kaman have a swashplate and blade pitch control links on their helicopters just like any other. The blade pitch control links are inside the hollow rotor shaft - the swashplates are inside the helicopter at the bottom of the hollow rotor shafts. Also instead of directly controlling blade pitch by using the pitch control links to twist the root of the blades ...


1

Don't Twist, morphing sounds torsionally flexible. Add mass to a soft spring and you get all kinds of resonances and eigenmodes. Better put the engine mass to a stiff and strong structure that can deal with its mass and forces.


0

The Wright brothers offset the engine to one side and the pilot to the other. The engine drove twin pusher props via bicycle chains. Outboard of that rigid centre section, control was by wing warping. Don't knock it, the plane flew on only 12 hp. But maybe you could improve on the bicycle chains. Another approach is to place the engines at the tail. In the ...


3

Image shows spoiler droop. Source: Delta A350 Landing - Detroit Metro (YouTube) Airbus calls the A350 flaps Adaptive Dropped Hinge Flap (ADHF). It's single-slotted, and Fowler motion is achieved by a deep pivot point, and the resulting gap is managed by spoiler droop, the latter increases the wing camber. (Spoiler droop is also used by the Boeing 787.) If ...


7

Adding to @Bianfable's answer, I'd like to address the terminology/usage. When referring to flaps on jetliners, single-slotted means single-slotted Fowler. The way a slot is created is in one of two ways: Fixed pivot point below the flap line (first image below) Slow airplanes Flaperons on jetliners Flaps extend backward and down (Fowler) Main flaps on ...


8

Airbus calls them single slotted, tracked high lift flaps in this presentation: When watching the flap extension in this YouTube video you can see that the flaps extend backwards and downwards at the same time, which would make them single slotted Fowler flaps:


0

Maybe within the wing towards the root, like in the concept of the Eather One (or de Havilland Comet). Otherwise, if it's a X-57-like concept, with distributed electric propulsion, I don't see why it couldn't work. Feather-tipped wings have made their way to Airbus' Bird of Prey conceptual proposal, although I don't know if that's the kind of biomimicry you ...


7

Those motors are only 4 hp each. I think you need a bit more juice to fly a Cri-Cri than 8 hp. The original's engines totaled 30 hp. Which means you need two 12 Kw motors. You need to then figure out where to put the batteries such that if they catch fire you won't turn into a roman candle. And once you have the motors and controllers and batteries and the ...


0

This question sets forth a project of considerable undertaking. Nevertheless, a relatively small wind tunnel is feasible, particularly for low-speed work (i.e. low Reynolds number), if there is willingness to use care and understand the technical issues in smoothing airflow and eliminating turbulence in the free stream flowing through the model test section ...


3

Short answer: Leading edge thrust. Slightly longer answer: Subsonic flow has the capacity to negotiate the leading edge, resulting in a suction peak which is missing in supersonic flow. Sweep allows to keep that flow pattern for as long as the flow speed component perpendicular to the leading edge is subsonic. This suction peak, acting on the forward-facing ...


0

As mentioned in this excellent answer, ground effect of aeroplanes can be modelled as extra lift from the mirror image of the plane. The image above depicts the effect on the tail plane, main wing is identical. This Prandtl Lifting Line Theory can be explained as extra lift from the mirror image of the wing. Torenbeek Appendix G.7 contains some expansion of ...


0

Setting the "experiment" aside for now, we can see that ground effect does indeed increase Lift. The first picture of the excellent reference Chapter 17 Ground Effect tells much. As one our most prominent writers often tells us, the vortex rolls off the entire trailing edge, not just at the wing tips. Further reading compares ground effect (on ...


1

As explained in another answer, keeping the wing inside the shock cone maintains the subsonic pattern of sideways flow which causes air to flow up around the leading edge. This allows you to use a rounded leading edge, which also works well at low speeds. But allowing the shock to meet the leading edge is not all bad. This is the condition in which the ...


4

TLDR; Subsonic perpendicular flow over the wing's front edge lets you optimise the wing for the subsonic take-off and landing. Don't be mistaken! The flow itself is still supersonic and you will still have to deal with shockwaves on your wing! You will not have (or at least it is very undesirable to have a strong shockwave in front of the aircraft) subsonic ...


0

You also require a means of smoothing out all the velocity gradients and eddies in the flow before it enters your test section. This is done my filtering the incoming air through a series of 10 or so screens with the fineness of a window screen, completely spanning the inlet cross-section, and set about 4 inches apart.


0

It depends on the cross-section and speed of airflow. The tunnel itself is just a duct. Is the power usage for fan that makes it expensive


5

Suction does. Air flow follows pressure gradients, and the lift-creating suction over the upper wing pulls in more air, not only from ahead of the airplane (which explains the induced angle of attack), but also from the side. The explanation of induced drag on the Boldmethod page is actually quite good; only gems like the wingtip vortices curve up and around ...


1

Your previous questions have already established that your professor oversimplifies things and has an issue with teaching basic concepts. That lets me assume that the aerodynamic center of the wing-body combination is the same as the aerodynamic center (a.c.) of the central wing (which is not true, but never mind). Otherwise this question cannot be solved. ...


2

I'll leave it for @Peter Kampf to explain the math, but I find it's easier to conceptualize static stability if you simply think of the airplane as a weathervane turned so its pivot axis is horizontal. Static stability simply is the forces making it point into wind, except the wind is changing in a vertical direction rather than a horizontal one. Instead of ...


2

This question is as much philosophical as anything else. All our mathematical models are only approximations which predict what will happen in certain circumstances. They do not necessarily address what is "really" going on. To take a common example from another field of engineering, is a given sound a particular waveform or a particular spectrum ...


6

Yes, all 10 passenger entry doors on the 747-400 main deck are plug-type doors: The main deck passenger entry doors are used to enter and exit the airplane, and serve as emergency exits. The ten passenger entry doors are paired along the airplane fuselage. [...] The entry doors are translating, plug-type doors. During opening, the door first moves inward ...


1

All of the force things we talk about in aviation are mathematical constructs. All Aerodynamic forces, Lift, Drag, Induced or parasite, on whatever vector direction you choose, are constructs. The only real forces that an aircraft (or any body in a fluid) feels, are the forces exerted by the little molecules bouncing off the surface of the body. Each time a ...


7

All of physics is artificial construct. Nothing of it is how the world actually works but rather our description of patterns we found in it. We do it using terms that exist only in our minds. So lift and drag, being terms, are artificial constructs. Now there is a pattern we always see in the world that we describe as conservation of momentum and ...


1

A helicopter applying downforce through its rotors would fall faster than a rock dropped next to it. Pulling out of that manoeuvre would demand excessive lift forces. Helicopters are not stressed for high manoeuvrability in the same way that some aircraft are, as the various forces imposed on the spinning rotor blades and driveshaft bearings would demand ...


1

During an autorotation the collective is lowered to its lowest position and this decreases the angle of attack (aoa) of the rotor blades. Once the helicopter begins its descent the resulting downward and forward profile creates a positive aoa for the blades. Maintaing the correct rotor RPM ( within a very narrow rage) is crucial in arresting the descent and ...


4

Pic source Negative thrust, as in enabling the helicopter to fly upside down...but no, the aerobatic Red Bull helicopter does not perform sustained inverted flight, it does barrel rolls and loops which maintain positive n. Providing negative collective is not a design feature in helicopters. Ray Prouty briefly discusses sustained inverted flight in ...


2

Dutch Roll is a 2-dimenional dynamic stability issue in aeroplanes. A little trolley towed by a car can be used to illustrate what happens, but the small amount of roll is purely an effect of directional instability, it is a one-dimensional issue. The pic above shows a damped dutch roll. The graph shows the two coupled variables, roll rate and yaw rate, ...


2

Wing sweep is best measured at the average wing cord. And for subsonic aeroplanes the average wing cord is at 25%, because that is where the aerodynamic centre is located. In the picture above we can see the linear forces acting on a wing, and the pitching moment $C_m$. We can choose any point on the wing cord to draw this vector diagram, but there is only ...


9

The dihedral effect is an opposing rolling moment induced by a sideslip. When an airplane is disturbed from wings level, it immediately starts to slip "downhill", slide sideways toward the low wing, in effect. The vertical fin starts to react to this after a certain amount of slip has developed, to realign the airplane with the airstream, ...


6

From your examples, the Cessna 172 is "in between". One key to understanding this is vertical Center of Gravity and how the plane behaves in a slip. Dihedral can be added to help roll away from the relative wind, as can a tall vertical tail fin or any area above the CG. But the main function of dihedral is for roll stability in straight line, ...


-3

The flipper ailerons are in direct line with the power pod allowing the engine thrust to pass the wing trailing edge.


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