# Tag Info

Accepted

### What stops a plane from rolling when the ailerons are returned to their neutral position?

Consider the relative wind on each wing. The falling wing has the relative wind coming from in front and below and the rising wing has the relative wind coming from in front and above. In other words, ...
• 16.9k

### How complete is our understanding of lift?

Many physical phenemona do not reduce down to an elementary algebraic equation. Aerodynamics -- including the generation of lift -- is very well understood. It has also been validated through ...
• 14.3k

### Are narrow propellers more efficient than wider ones?

Propeller chord is determined by the power which needs to be absorbed by the prop. As with wings, propeller blades perform best in a small band of lift coefficient values: Too high, and drag will ...
• 234k

### How do aeroplane wings work?

I think your fundamental premise is unfortunately false. Kepler's laws were purely empirical. He had no actual theoretical basis for them. He used a tremendous amount of data (thanks to Tycho Brahe) ...
• 14.3k
Accepted

### Why will a positive stagger increase biplane efficiency, while a negative stagger will decrease efficiency?

Because we look only at efficiency at positive lift. Remember that increasing the distance between the wings of a biplane increases efficiency (see for example Table III in Max Munk's NACA report 151)....
• 234k

### Does dynamic stability decrease with airspeed

Is it true that dynamic stability diminishes as airspeed increases? Yes, when the solid body eigenmodes are concerned. In aerodynamics, dynamic stability is mainly achieved in two ways: Secondary ...
• 234k

### Is it pragmatic to use slats and flaps to maintain position of center of lift?

I have been wondering for some time about whether you could design a system of slats that deploy... to prevent the nose down pitch moment. The idea is to bring the relative aoa back to what it was ...
• 14.1k

### Why will the bending of air over an airfoil make a force?

Imagine yourself on a cart with very low friction wheels on a plain and smooth surface. With you on that cart you have a supply of tennis balls. Or brass ingots, doesn't matter as long as what you ...
• 234k

### Could an aircraft possibly achieve a vertical nose dive at 90 degrees without breaking up?

Normal transport aircraft (FAR Part 25 certification) have structural design cruise speed called VC. These aircraft must demonstrate that they can achieve a maximum dive speed VD. This speed must ...
• 14.3k

### How to make an airplane less bumpy?

When you say weight -- a heavier aircraft is less bumpy, what you're really after is the wing loading. A heavier aircraft with a smaller wing will be less bumpy. The bigger the wing, the more ...
• 14.3k

### Why does forward CG decrease controllability/maneuvarability?

Intuitively: the farther forward from the center of lift that the CG is, the greater the "lever arm" that inertia has in keeping the airplane doing what it's trimmed for. That effect ...
• 12.3k

### Will the 3D effect change shockwave angle/strength?

Is the cone an infinite cone? If the cone is finite -- like all real cones -- then there will ben an expansion fan off of the end of the cone that will interact with the shock and will bend it. ...
• 14.3k
Accepted

### What type of airfoil should be used for horizontal tailplanes?

Most statically stable aircraft with the tail aft have a download on the tail. The most efficient way to do that is with a horizontal tail with a cambered airfoil -- placed upside down. This ...
• 14.3k

### Does the pressure recovery become not as extreme as you speed up?

I find it very hard to understand your questions because you choose strange wording for things which have proper names already. Why should there be a change in the pressure distribution as speed ...
• 234k
Accepted

### Why is there an area of different density right at the nose of a plane going supersonic?

The main thing you are seeing here is an artifact that the image is a sum of a bunch of 3D layers -- not just a 2D slice. The nose of the airplane is a cone, so the flow structures happen in 360 ...
• 14.3k

### Is it pragmatic to use slats and flaps to maintain position of center of lift?

Flap pitching moments are normally nose down with extension, although some airplanes pitch up with flap because nose-up trim changes from increased downwash on the tail overpower the nose-down trim ...
• 132k

### What's the optimal taper ratio for a commerical short/medium haul aircraft?

Taper ratio is mainly used to control how lift is distributed spanwise with the goal of having an elliptical distribution in order to reduce induced drag. The following plot represents how lift ...
• 14.1k

### Why will the bending of air over an airfoil make a force?

air never pulls anything. Only pushes. Not quite right. On a molecular level, viscosity of moving air does pull in surrounding air. But in the lift case, you are right. Air from underneath the ...
• 20.6k

### Why will the bending of air over an airfoil make a force?

The objective of a cambered wing is to tilt the momentum vectors of oncoming air parcels downwards. This requires the wing to apply a force to the air as it passes by and the reaction force is equal ...
• 21.8k

### What type of airfoil should be used for horizontal tailplanes?

I think your doubts arise from confusing the aerodynamic characteristics of a cambered airfoil versus an uncambered aka symmetrical airfoil. The following plot shows the lift coefficient for a ...
• 14.1k

### Are narrow propellers more efficient than wider ones?

I think here there's both a clever use of the structural characteristics given by carbon fiber and some marketing at work. We can try to answer this question using one of their documents (PDF) to ...
• 14.1k

### Could an aircraft possibly achieve a vertical nose dive at 90 degrees without breaking up?

I assume your question is to exclude fighter jets and unlimited category aircraft which by design certainly can do pretty much everything, the physiology of the pilot being the limiting factor. First ...
• 29.3k

### Is washout a twist up at the root or a twist down at the tip of the wing?

Washout is chordline twisting nose down toward the tip. When it starts is not important. There is washout if the angle of incidence of the tip is lower than the root. Wash-in is the opposite. ...
• 132k
1 vote

### How to make an airplane less bumpy?

Here are some ways to reduce bumpiness. design the plane to fly higher, where the air is less bumpy. design the plane to fly faster, so it spends less time in a rising or descending air column so ...
• 21.8k
1 vote
Accepted

### How does lift depend on velocity in 3D?

The code you are using needs the velocity as given in your equation 2. because this is how lift and drag are defined/calculated in that code. The velocity component "coming out of the paper" ...
• 14.1k
1 vote

### Is it pragmatic to use slats and flaps to maintain position of center of lift?

There are two answers to what you are asking, here: Slats are not used for this, as slats have very little effect on coefficient of moment. There is no aircraft (that I'm aware of, at least) which ...
• 11
1 vote

### Is it pragmatic to use slats and flaps to maintain position of center of lift?

Do not focus on the slat alone, you have to keep the whole system in mind. Slats generate lift ahead of the c.o.g., but they also deflect the air downwards (Dumping velocity). The incoming air thus ...
• 7,667
1 vote

### Is it pragmatic to use slats and flaps to maintain position of center of lift?

Right at the moment when flaps are deployed, we actually experience a nose up movement, at least in the planes that I've flown so far. Anyway... Remember that drag is a side effect whenever we want to ...
• 521
1 vote

### Will the 3D effect change shockwave angle/strength?

It sounds like the thrust of your question is about whether the wave front will begin to develop 'gaps' like in your analogy of the ball being thrown up from different angles. The issue is that the ...
1 vote

### Is a Tandem more efficient than a Biplane?

Considering both airplanes have 2 wings The premise of your question is not correct: the Q2 has one wing and one horizontal empennage while the Skybolt has... well, one wing and one horizontal ...
• 14.1k

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