Why is carburetor icing dangerous and how can it be prevented or mitigated?

• A. It can improve engine power; no prevention needed.
• B. It has no effect on performance.
• C. It can cause loss of power; prevent by applying carburetor heat and monitor for RPM drop.
• D. It only occurs at high altitude.

Answer: (C)

Carburetor icing happens when moist air enters the carburetor and some of it freezes in the venturi, narrowing the air passage. That restriction reduces the amount of fuel-air mixture reaching the engine, causing a drop in engine power, rough running, and potentially a complete loss of power if the icing worsens. This is dangerous because a sudden loss of power at low altitude or during maneuvering can lead to an out-of-control situation or an inability to maintain airspeed and altitude.

The primary way to prevent or mitigate icing is to apply carburetor heat. This introduces heated air (often taken from around the exhaust) into the carburetor, melting existing ice and reducing further ice formation. When carb heat is applied, you’ll typically see a brief drop in RPM as the air becomes less dense and the mixture changes; if the RPM recovers and the engine runs smoothly again, icing is being mitigated. If the RPM does not recover, or performance remains rough, you should descend and seek a safe landing while keeping an eye on engine indications.

Carburetor icing can occur at any altitude and in humid conditions near freezing, not just at high altitude, so it’s important to be vigilant and use carb heat when you suspect icing or when operating in conditions conducive to it.