11k views

### What is the relation between an airplane's altitude and the drag it is experiencing?

The Reynolds-Number $Re$ is defined as $Re = \frac{c \cdot L \cdot \rho}{\mu} = \frac{c \cdot L}{\nu}$, with the velocity $c~\left[ \frac{m}{s} \right]$, the reference length $L~\left[ m \right]$, ...
2k views

### If I were to build a J3 cub twice the size of the original using the same CG would it fly?

How big of an engine would I need, if the original is 65hp? What would be the weight of the up-scaled plane? Simply twice the weight? What would be the stall speed? How fast would it go? 75mph? Is ...
2k views

### Is drag coefficient lowest at zero angle of attack?

The drag coefficient of a symmetric airfoil is lowest when its angle of attack is zero. I'm not sure if this is true in general.
706 views

### How does the power requirement change when weight and speed change?

Suppose I have an airplane with a certain weight M, which uses a certain amount of power P, to fly at a certain speed V. If I use the same airplane, but quadruple the weight (4xM) and double the ...
3k views

### What is the total wing surface area of the A320?

I was trying to calculate the total area of an A320, and in this link I found the wing area and tail area. But here I read that the wing area is just the 2D projection of the wing. So if I wanted to ...
868 views

### What is the purpose of thinner airfoils used near wing tips?

I know that a thicker airfoil at root will strengthen the root spar but what is the reason behind using thinner airfoils at the tip? Is it because thinner airfoils have higher stalling angles of ...
2k views

### Is airfoil thickness proportional to drag coefficient?

Does increase in the thickness of a camber airfoil mean more drag will be produced? Why do slow flying planes have thick airfoils when it will just slow them down even more?
877 views

### What creates most drag during flight: fuselage or wings?

From pic 1, I know the drag line is below the thrust line, but I am puzzled about where the drag line is in pic 2? Secondly, what creates most of the drag in flight, is it the fuselage or the wings?
6k views

### How to pick a good airfoil based on Cl and Cd

Let's assume I have 10 different airfoils graphs of Cl x Aoa, Cd x Aoa and Cl/Cd x Aoa. How do I pick the best one that will give me the most efficiency (the longest flight time)? I understand the ...
271 views

### Will this simple equation (pic attached) produce a rough estimate of the top speed of a prop driven aircraft?

Calculating the approximate top speed of a vehicle is straightforward. $v = \sqrt[3]{\frac{2P}{c \cdot D \cdot A}}$ where v = velocity of the vehicle P = power of the engine c = coefficient of ...
704 views

### Does anyone know an equation relating wingspan to gliding distance for a glider?

I found this equation online but it is not from a reputable source and has no derivation. Could anyone help me by deriving this equation or even verifying its accuracy? I would love to cite and use ...
2k views

### Is it possible to determine the approximate climb rate of an aircraft knowing its top speed, engine power and weight?

Is it possible to determine the initial climb rate of a craft with a few key pieces of data such as top speed, engine power and weight? For example the XB-42 was an experimental bomber design from ...
7k views

### How is the zero-lift drag coefficient calculated?

The drag coefficient is usually given as a funtion of the lift coefficient and the zero-lift drag coefficient ($c_{D0}$): $c_D=c_{D0}+k\cdot c_L^2$ How can I calculate/estimate $c_{D0}$?
867 views

### Are there any reference values for Cl and Cd of a NACA 0012 airfoil to verify CFD simulations?

I am having trouble finding the established results of inviscid flow CL and Cd variation over NACA 0012 airfoil, for the transonic region. I need the data to verify the results I am getting through my ...