# What is the relationship between stall lift and drag

### Stall (fluid dynamics) - Wikipedia

Aerodynamic Lift and Drag and the Theory of Flight. It shows the superior lift characteristics and higher stall speed of aerofoils compared with a simple flat. Combine this drag with the "real" lift, including losses due to separation, lift-to- drag ratio of the aircraft between separation onset and stall. The angle between the chord line and the flight direction is called the Predicting the stall point (the angle at which the wing stalls) is very.

There's no conservation of energy here.

• Lift-to-drag ratio

In the second example we add a degree wall. One could ask, "What angle of a single deflection plate would provide the largest change in direction? The thing about Aerodynamics is that we deal with fluids rather than solids. So it is a little bit different. So here we introduce things like "eddy currents" like those circular whirlpool like things forming behind a fast moving boat which are the result of the fluid trying to fill the gap left behind by the moving object we're dealing with, which is a wing.

A wing deflects airflow downwards. Most of us who know how Newton's physics works know that a wing gains lift by pushing airflow downwards and the momentum of the air has an equal and opposite reaction of pushing the wing upwards.

## What is a Stall?

Because the airflow starts to fall back onto the back of the wing and pushing it down even at small angle of attacks, people in the aviation industry usually refer lift production as the lack of airflow pressure on the top of the wing rather than the bottom of the wing pushing airflow down.

Now back on-topic, with stalls. The start of a stalling point is usually defined as the point where increasing the angle of attack results in no additional lift production. In other words, the wing to airflow angle exceeding the critical angle of attack. The inefficiency of conversion of momentum See the ball and plate example 2.

Eddy currents forming on the wing See above image Because fluids are more unstable and have a tendancy to "fill the gap" usually what causes the "stall" is point number "2.

It still produces lift. Just not the desired amount, and pulling back on the stick results in lesser lift production. Even in Autorotation you still produce lift. It's the reason why it's so hard to get out of a spin - because your wings do not want to duck under the other one due to your own aircraft's stability.

Airflow has a higher tendancy to form eddy currents as airspeed increase so that becomes a more limiting factor and angle of attack where the Critical Angle of Attack occurs is not actually consistant and can vary from as high as 22 degrees or even higher to very low, so low that the plane could be in its "coffin corner" altitude. Usually the stalling effect on control surfaces ailerons, elevator flippers, and rudder is dubbed as "compressibility" issues but really is just the airflow gone wonky and not flowing constantly anymore, or the pilot is unable to provide the force to deflect the control surface.

These are two completely different things indeed but that's how pilots dub it. Blame the ones who defined it. Serpooshan Aug 27 '17 at 9: The last paragraph is for drag estimation of the full aircraft once separation starts.

It does not explain the changes in lift which is what the rest of the answer tries to do but the increase in drag. Anderson Jr Fifth edition, page I just copy and paste in the case you don't have the book: Here the airfoil at a large angle of attack thus with flow separation is shown with the real surface pressure distribution symbolized by the solid arrows.

Pressure always acts normal to the surface. Hence the arrows are all locally perpendicular to the surface. The length of the arrows is representative of the magnitude of the pressure. However,if the flow were not separated, that is, if the flow were attached, then the pressure distribution would be that shown by the dashed arrows and the dashed envelope.

The solid and dashed arrows in Figure 4. They explain the two major consequences of separated flow over the airfoil. Therefore, when the aircraft pitch increases abnormally, the canard will usually stall first, causing the nose to drop and so preventing the wing from reaching its critical AOA. Thus, the risk of main wing stalling is greatly reduced. However, if the main wing stalls, recovery becomes difficult, as the canard is more deeply stalled and angle of attack increases rapidly.

In this case, the wing can be flown at higher lift coefficient closer to stall to produce more overall lift. Most military combat aircraft have an angle of attack indicator among the pilot's instruments, which lets the pilot know precisely how close to the stall point the aircraft is.

Modern airliner instrumentation may also measure angle of attack, although this information may not be directly displayed on the pilot's display, instead driving a stall warning indicator or giving performance information to the flight computer for fly by wire systems. Flight beyond the stall[ edit ] As a wing stalls, aileron effectiveness is reduced, making the plane hard to control and increasing the risk of a spin starting.

Post stallsteady flight beyond the stalling angle where the coefficient of lift is largest requires engine thrust to replace lift as well as alternative controls to replace the loss of effectiveness of the ailerons. For high-powered aircraft, the loss of lift and increase in drag beyond the stall angle is less of a problem than maintaining control.

Some aircraft may be subject to post-stall gyration e. Control beyond-stall can be provided by reaction control systems e. NFAvectored thrust, as well as a rolling stabilator or taileron.

## Stall (fluid dynamics)

The enhanced manoeuvering capability by flights at very high angles of attack can provide a tactical advantage for military fighters such as the F Raptor. Pugachev's Cobra are sometimes performed at airshows. Spoiler aeronautics Except for flight training, airplane testing, and aerobaticsa stall is usually an undesirable event.

Spoilers sometimes called lift dumpershowever, are devices that are intentionally deployed to create a carefully controlled flow separation over part of an aircraft's wing to reduce the lift it generates, increase the drag, and allow the aircraft to descend more rapidly without gaining speed.

Spoilers can also be used on aborted take-offs and after main wheel contact on landing to increase the aircraft's weight on its wheels for better braking action.

Unlike powered airplanes, which can control descent by increasing or decreasing thrust, gliders have to increase drag to increase the rate of descent. In high-performance gliders, spoiler deployment is extensively used to control the approach to landing.

### Angle of Attack - Relationship of Lift and Drag - ZdrytchX's {Reference Webpage

Spoilers can also be thought of as "lift reducers" because they reduce the lift of the wing in which the spoiler resides. For example, an uncommanded roll to the left could be reversed by raising the right wing spoiler or only a few of the spoilers present in large airliner wings. This has the advantage of avoiding the need to increase lift in the wing that is dropping which may bring that wing closer to stalling.

History[ edit ] Otto Lilienthal died while flying in as the result of a stall.

Lift, Coefficient of Lift

Wilbur Wright encountered stalls for the first time inwhile flying his second glider. Awareness of Lilienthal's accident and Wilbur's experience, motivated the Wright Brothers to design their plane in " canard " configuration.

This made recoveries from stalls easier and more gentle. The design saved the brothers' lives more than once. In developing the resulting " autogyro " aircraft, he solved many engineering problems which made the helicopter possible.