⚠ What Happens When Ice Builds Up
Before we explain anything — just feel it. Drag the slider to watch an airplane's performance fall apart over 60 minutes of icing:
❄ Ice Accumulation Simulator
Where does ice accumulate on the airplane?
Ice builds on every exposed frontal surface: wing leading edges, propeller, windshield, antennas, air intakes, vents, and engine cowlings. It can build in spots where no heat or deicing boots can reach it. In moderate-to-severe icing, a light aircraft can become so loaded with ice that continued flight is impossible.
🌡 How Does Ice Form?
Ice doesn't just appear. You need all three ingredients at the same time. Remove any one and you're safe. Tap each to learn more:
💧 Ingredient 1: Visible Moisture
🌡 Ingredient 2: Freezing Temperature
✈ Ingredient 3: An Aircraft Flying Through It
The Escape Logic
Every escape strategy works by removing one ingredient: exit the clouds (remove moisture), descend to warmer air (remove freezing temp), or change course (remove yourself). Take away any one and ice stops forming.
Icing Is Cumulative
This is critical: icing doesn't stop. It just keeps building. The longer you stay in icing conditions, the worse it gets. There's no "it'll level off" — it's a one-way ramp to disaster.
🗺 How Icing Happens — Visual Scenarios
Let's look at the most common icing situations. Click each diagram to explore what's happening in the atmosphere:
❄ So What Is Icing, Exactly?
Now that you've seen how bad it gets — let's back up. Icing is when ice builds up on the outside of your airplane while you're flying. Ice sticks to your wings, propeller, windshield — any exposed surface.
Sounds simple, right? But even a tiny amount completely changes how air flows over your wings. And your wings need smooth airflow to keep you in the sky.
🎓 Think of It Like This
Your wing is designed like a perfectly shaped airfoil — smooth, curved, and precise. Every millimeter matters. Now imagine gluing sandpaper to the front edge. The air can't flow smoothly anymore. Lift drops. Drag skyrockets. That's exactly what ice does.
It's Not About the Weight
Most people assume ice is dangerous because of the added weight. Nope. The actual weight of ice is almost insignificant. The real killer is how ice disrupts airflow over the wing, destroying lift and massively increasing drag.
Why is icing dangerous to aircraft?
❄ The 3 Types of Ice
Not all ice is the same. The type depends on temperature and droplet size. Click each type to explore how they look, form, and how dangerous they are:
Rime Ice
Think of rime ice like frozen spray paint. Small supercooled droplets hit the wing and freeze on contact, trapping air in the process. The result is a rough, white, frosty coating. It's the most commonly reported type of icing.
The good news: it usually responds to deicing equipment. The bad news: its rough, jagged surface seriously disrupts the smooth airflow your wings need to generate lift.
Clear Ice (Glaze)
This is the villain of the icing world. Large supercooled droplets don't freeze instantly — they flow over the surface before solidifying, creating a smooth, glassy sheet that's nearly invisible.
Clear ice forms dangerous "horns" on the wing's leading edge that completely destroy airflow. It's dense, hard to remove, and can spread beyond where deicing boots reach. You might not even realize it's forming until your performance has already degraded.
Mixed Ice
Mixed ice is exactly what it sounds like — a sandwich of rime and clear ice. As you fly through varying temperatures and droplet sizes, you collect alternating layers. When you cut through it, it looks like layers of a cake.
It combines the worst aspects of both types: can form horns like clear ice, spreads over large areas, and is harder to remove than rime alone.
Memory Hack
Rime = Rough & Rapid (small drops, instant freeze, frosty look)
Clear = Creeping & Clear (big drops, slow freeze, glassy look)
Mixed = Marble cake (layers of both)
✈ See It On The Wing
Click the buttons to see how each type of ice changes the wing's shape and disrupts airflow:
🌎 Where You'll Find Icing
Icing doesn't happen everywhere. Tap each situation to learn what to watch for:
🌩 In Flat, Layered Clouds (Stratiform)
Icing in stratiform clouds is usually in a layer 3,000–4,000 ft thick. Changing altitude by a few thousand feet often gets you out. Intensity is usually light, worst near cloud tops. But these layers can stretch for hundreds of miles. Below -20°C, stratiform clouds are mostly ice crystals and produce little icing.
⛈ In Towering Clouds (Cumuliform)
Smaller horizontal area but much greater vertical extent. Intensity ranges from trace in small cumulus to severe in thunderstorms. Worst in the upper portion where the updraft is strongest. Strong updrafts keep water liquid down to -40°C!
🌀 Near Weather Fronts
Most icing reports come from near fronts. The most dangerous scenario: freezing rain below a warm front. Rain forms in warm air above, falls through cold air below, becomes supercooled, and freezes on contact with your airplane. Ice pellets at the surface = severe icing above.
⛰ Near Mountains
Mountains force air upward, creating supercooled water above the freezing level. When a front crosses a mountain range, the combined lift creates extremely hazardous conditions. Worst zone: windward side, up to 5,000 ft above peaks. Terrain may prevent you from descending to warmer air.
⚡ Inside Thunderstorms
Abundant supercooled water above the freezing level. Clear icing accumulates very rapidly between 0°C and -15°C. Encounters can be frequent in a cluster of cells. Thunderstorm icing is extremely hazardous.
You're at 8,000 ft, OAT is -10°C, flying through a layer of stratus clouds. You notice a thin white coating building on the wing leading edges. What type of ice is most likely forming?
💧 Going Deeper: Supercooled Water
Now that you understand the basics, let's dig into why water stays liquid below freezing. This is one of the most fascinating parts of aviation weather.
Here's something wild: pure water suspended in air doesn't always freeze at 0°C. Tiny cloud droplets can stay liquid all the way down to -40°C! This is called supercooled water, and it's the reason aircraft icing exists.
🧊 Why Doesn't It Freeze?
Surface tension. The smaller and purer a water droplet, the harder it is for ice crystals to form inside it. The droplet's surface tension holds it together as a liquid even well below 0°C. But the instant it's disturbed — like smacking into your wing — it freezes almost instantly.
Drag the temperature slider to explore what's happening inside a cloud at different temperatures:
What are Supercooled Large Drops (SLD)?
SLDs are supercooled drops larger than 40 microns — things like freezing drizzle (40–200 microns) and freezing rain (>200 microns). They're extremely dangerous because they flow along the airfoil before freezing, forming lumpy ice that spreads far beyond where deicing boots can reach. SLD ice can act like a spoiler, creating dangerously unstable flying conditions.
Why does supercooled water exist?
📊 What Makes Icing Worse?
Not all icing encounters are equal. Three key factors determine how bad it gets:
How much water is in the cloud
Colder isn't always worse
Bigger drops = worse ice
💡 It's Not Just Weather — Your Airplane Matters Too
Airspeed: Faster planes collect less ice because skin friction heats the surface. Above 575 knots, icing is negligible.
Aircraft type: Commercial jets at high altitude are generally less vulnerable than slow, low-flying turboprops and piston aircraft. Light trainers (like a Cessna 172) are among the most vulnerable.
Can you pick up ice on the ground?
Yes! If your airplane was "cold-soaked" from flying at altitude, the airframe can stay below 0°C even after landing in warm air. Aircraft with fuel tanks flush to the airframe are especially susceptible — they can collect ice even when the air temp is above freezing.
🔨 Carburetor Icing
This one catches people off guard. Carb ice can form on clear, sunny days with temps up to 100°F. Adjust the sliders to see when you're at risk:
How It Works
The carburetion process drops air temperature by up to 38°C (100°F). Even on a warm day, the air inside the carburetor can drop below freezing. If there's enough moisture, ice forms on the throttle plate and venturi, choking off air to the engine.
Signs: Unexplained RPM drop (fixed pitch) or manifold pressure drop (constant speed). Apply carb heat immediately!
🚨 What To Do — The Escape Plan
You've picked up ice. Now what? Your first priority is always to leave the icing conditions, regardless of whether you have deicing equipment.
cloud bases
cloud tops
different course
above 0°C
You're approaching a mountain ridge from the windward side at 9,000 ft. OAT is -8°C, you're in clouds, and moderate rime ice is building. The ridge tops are at 7,500 ft. What's your best move?
🏆 Final Review
Let's see how much you've learned! First, a matching challenge, then a 5-question exam.
🎯 Match the Term
Click a term on the left, then click its matching description on the right.
🧠 Icing Exam
1. At what temperature does the physical cold limit to icing occur?
2. What do ice pellets at the surface indicate about conditions aloft?
3. Which icing type forms "horns" and is hardest to detect visually?
4. What are the 3 most important factors for icing type and severity (in order)?
5. A pilot in a Cessna 172 encounters moderate icing. First action?