Airfoil

Airfoils (Element) provide atmospheric lift to construct in proportion with its velocity. They do not consume fuel but demand proper placement for optimal usage. There are 3 types of airfoils, which differ in size mass and stall angle. Users often use "wing" as synonyme for airfoil.

## What is Drag, Stall and Lift.

### Drag

Drag is mostly generated by the ship itself in form of air resistance due to cross section. While airfoils in DU have a "lift to drag ratio", it can just be ignored, just like their fuel consumption stat.

### Stall

The stall angle is the angle at which an airfoil no longer creates any lift. For a wing this is 55°. Approaching this limit the maximum force available goes down be the factor root(cos(A)) for an angle of A. So in practice, should a player yaw to the point of drifting sideways, the lift produced goes from 100% at forward direction down to 75% of force at a 55° angle towards current direction of movement, and then suddenly drop to 0%.

While a loss of lift due to slowness is also generally called stall outside of DU, in DU stall should only be used for loss of lift due to direction, to avoid confusion.

### Lift

As long as a craft is moving and the airfoils on it are pointing roughly in the same direction (within their stall angle), they provide lift. If that lift is higher than the force of gravity at that location, the craft can fly.

## Different Airfoils.

### Aileron

Ailerons (and compact ailerons) are usually placed in the back of the craft due to their shape. While visually pleasing they have a low stall angle (30°) and poor lift for their size and mass

### Stabilizer

These have a very high stall angle (70°) and are the only airfoil with an L sized element. They do however have poor lift relative to their size and mass

### Wing

Wings have the best lift for their size and mass with a still very nice stall angle of 55° and are the default for most crafts up a certain size (see element number bug below).

### Sizing

A one bigger airfoil generally has 4x the lift, but 5x the mass and in excess of 5x the size, depending on how you want to measure it. As such, just going be the numbers, a high number of small elements is best. In practice however, repairing a low amount of bigger elements is more convenient, placing is easier, and bigger elements are often more visually pleasing.

If you are a new player and have issues taking off, wing M is king. For anybody else, take whatever looks nice.

### Active element number bug

The game struggle when the amount of elements relevant for flight gets too high. Depending on factors like PC hardware, connection, amount of visible other constructs and terrain a ship will fly at lower than displayed speed. A trip of 100km at 1000km/h will take longer than the obvious six minutes. Due to this, bigger haulers (very roughly once being able to carry above 5kt) should be build with "force per element" in mind. Using only the biggest elements of each kind. In case of airfoils, that means using stabilizers L, even though they have very poor stats for their size. Even on smaller crafts, having above 100 airfoils of any kind should usually be avoided, and bigger airfoils be used instead.

### Further information

The page on sustentation speed includes more information and math regarding lift.