# Tag Info

### Database for NACA airfoil polars

The technical report NACA-TR-824 has been digitized. The digitized version includes Cl and Cd for 118 airfoils at 3 Reynolds numbers. To get it, create an account on x-plane.org. (It's been online ...
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Accepted

### Do the polar curves have large differences in takeoff than in landing?

Yes, in most cases. How large? That depends. A classic simple flap does these things to lift: Adds an approximately constant amount of lift at a given AoA in the linear range. For small flaps ...
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### Do the polar curves have large differences in takeoff than in landing?

The $C_L(\alpha)$ curve changes with flap/slat extension, so it should logically follow that the polar will also change, since the induced drag depends on the lift. Furthermore the parasite drag will ...
Accepted

### How does pitch relate to glide angle?

When you pitch the nose down to gain speed, it feels as though you are pitching down a long way This is because the change of the cockpit angle towards the horizon is the sum of both the angle of ...
• 217k

### What does "E" stand for in a polar curve?

E is used as the symbol for L/D in German. Normally, a symbol description will call it "Gleitzahl" (glide ratio).
• 217k
1 vote

### What would be a good way to present airfoil performance diagrams and requirements to aircraft designers?

Problem with a potential one-stop, simple solution for this is the multi-dimensional matrix that is aeroplane design. Aeronautical engineering is complicated. Wing design is a chapter in Torenbeek ...
• 57.7k
1 vote

### How does pitch relate to glide angle?

Pitch attitude in itself isn't the big factor, other than as a speed control tool (in gliders). It's mostly about whether or not the position of the spot on the ground you're approaching changes (...
• 103k
1 vote

### How do I calculate new minimal speed for a glider when I put water into the tank?

$v_2 = v_1 \cdot \sqrt{m_2/m_1}$ is the correct formula. $v_2 = v_1 \cdot m_2/m_1 = 87km/h$ is simply wrong, possible that it is only a typing mistake, but it is wrong just the same.
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1 vote

### Why is polar curve of a glider dependent on flight load?

Oh god- I made a terrible mistake: While $C_{lift}$ and $C_{drag}$ are really independent on weight, this is (of course..) not the case for the velocity polar curve. The two curves scale perfectly ...
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