If you examine the wings on almost any aircraft, you’ll first notice the aerodynamic shape that help all aircraft to have lift. But something you might not notice as easily is a design feature called “wash out”.
The purpose of wash out is to help make the aircraft more stable during a stall. But what does it look like and how exactly does it work?
We’ll answer all of those questions and more in this article!
SUMMARY
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Washout is a subtle wing design feature for flight stability and stall recovery.
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Washout sees that the wing root stalls before the tips.
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This design is common in general aviation, gliders, and commercial aircraft.
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Washout helps pilots appreciate how aircraft are engineered.
What is Wing Washout?
A washout is a deliberate design characteristic where the wingtip has a lower angle of incidence than the wing root.
To help explain it better, it means that as an aircraft approaches a stall, the root stalls first, while the tips continue generating lift. This helps to create both better control and stability for the aircraft.
You can try to spot "washout" on a wing by examining the wings from the front of the aircraft and observing the twist that forms from the root to the tip. The root will have a higher angle of incident than compared to the tip of the wing.
How Wing Washout Affects Lift Distribution
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The difference in angle of incidence along the wingspan causes a progressive stall pattern.
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Washout makes sure that the wingtips remain flying while the root stalls. Pilots end up retaining roll control through the ailerons.
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Washouts help to create a controlled stall behavior that reduces the risk of unintended spins and can help with stall recovery.
The Purpose of Washout in Aircraft Design
Aircraft wings are designed with washout to address stall issues. As you examine the leading edge of the wing, you'll notice the root, which is the point where the wing attaches to the aircraft's body.
The twist at the wing tip sees to it that the root, which has a higher angle of attack, reaches its critical angle of attack before the tip does, leading to a stall at the root first.
This prevents the entire wing from stalling and is often called a "structural washout", versus the aerodynamic washout.
Structural vs. Aerodynamic Washout
As mentioned at the end of the previous section, there are two types of washouts: a structural washout and an aerodynamic washout.
But still, what is the difference between the two? Let's explore those.
Structural Washout
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A structural washout is achieved through physically twisting the wing so that the tip has a lower angle of incidence than the root.
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This kind of washout is most common in fixed-wing aircraft like the Cessna 172, that has around 3° of washout.
Aerodynamic Washout
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Is accomplished by using different airfoil shapes, vortex generators, stall strips, or wing cuffs.
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You'll see this in aircraft like the Cirrus SR-22. It uses cuffed wing sections to help maintain control while at high angles of attack.
How Does Washout Work?
When an aircraft increases its angle of attack, the root reaches the critical stall angle first due to its higher incidence. This allows the tips to continue generating lift, preventing sudden roll-offs that could lead to a spin.
Washout in Stall Scenarios
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Straight and level flight → Both root and tip generate lift normally.
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Approaching stall → The root experiences separation first, while the tip still provides lift.
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Full stall → The root is completely stalled, but the tips maintain airflow for recovery.
Washout and Different Aircraft Types
General Aviation Aircraft
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Most small aircraft, like Cessna 172s, use washout to help provide stall stability.
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Prevents sharp rolling moments during a stall.
Gliders & Hang Gliders
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Washout reduces adverse yaw and improves slow-flight stability.
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It's used to minimize drag and optimize glide performance.
Military & High-Performance Aircraft
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Some fighter jets use reverse washout (wash-in) to improve high-speed maneuverability.
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Washout is less common in aerobatic plane because they require symmetrical flight characteristics.
What to Look for:
Want to know how to spot washout? Here's how:
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Often on aircraft the trailing edge near the wingtip is angled slightly downward compared to the root. This is because it has a decrease in the angle of incidence from root to tip.
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You can see from how the ailerons and flaps are aligned that they're done in a way where the wingtip's chord line is at a lower angle relative to the root.
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If the aircraft wing has winglets, the winglet will be located at the wing tip and it's oriented to reduce drag. It is often paired with washout to help the aircraft maintain its control effectiveness in stall conditions.
Washout vs. Wing Twist: What's the Difference?
There is a difference between having a twist in a wing or specifically a wash out.
Key Differences
|
Feature |
Washout |
Wing Twist |
|---|---|---|
|
Definition |
Decreasing angle of incidence from root to tip |
A general twisting along the wing’s span |
|
Purpose |
Helps to improve wing stalls and characteristics, stability, and control |
Can be for structural integrity or aerodynamic efficiency |
|
Example |
Cessna 172 (3° washout) |
Some fighter jets with intentional wash-in for their maneuverability |
Frequently Asked Questions
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What is the main reason for using washout in wings?
Washout makes sure that the wing root stalls before the tip. it's meant to maintain control and prevent dangerous roll tendencies.
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Do all aircraft have washout?
Most aircraft designed for stability and safety mix in some degree of washout, but aerobatic and fighter planes may have little to none.
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Can washout be adjusted after aircraft construction?
Yes, minor washout changes can be made using aileron rigging, stall strips, or leading-edge modifications.
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How much washout is typical in small aircraft?
Light aircraft like the Cessna 172 typically have around 3° of washout, while other designs may vary based on their aerodynamic needs.
Takeaway
Now you know that a washout is an amazing design feature that helps to improve an aircraft’s stability, stall behavior, and gives the pilot more control.
Just remember that the wing root stalls before the tips, the washout maintains aileron effectiveness, and it prevents sudden roll-offs and reduces the risk of spins. That's a mouthful to say, but it's important to remember.
It is pretty common in general aviation, commercial aircraft, and also in gliders. Some high-performance and aerobatic aircraft might not use washout, but that's because they need the maneuverability.
Don't shy away from learning more about engineering and aerodynamics. Flight and how it works is an amazing this and one of the greatest accomplishments of mankind.
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