Rough Air Over the Gulf

Departing Venice Municipal Airport (KVNC), Venice, FL — Runway 04, climbing out on a 045° heading. Elevation 18 ft MSL; the runway is essentially at sea level. Non-towered field, Class G airspace, CTAF 122.8.

It is a humid Gulf Coast morning in late spring: OAT 26°C, dew point 21°C, altimeter 29.94. Scattered clouds at 2,800 ft, light rain shower two miles to the northeast. Visibility 7 SM. The FAA icing probability chart marks these exact conditions as 'serious icing at glide power, moderate icing at cruise power.' The relative humidity is 87% — classic carburetor ice weather.

You are 350 ft AGL, climbing through 68 KIAS (Vy for the C150M at gross weight), heading 045°, when the engine begins to run rough. Power is noticeably down — the tachometer is dropping. The engine is not surging; it is simply losing power. You are still over the airport environment, but altitude is low and the climb is shallow.

Aircraft: Cessna 150M, solo, full fuel (38 gallons), within limits. Continental O-200-A, 100 hp, carbureted, fixed-pitch prop, steam panel. Nothing was written up; the airplane was airworthy at departure. This is the third flight of the day; the airplane has been running fine on the previous two legs.

Pilot: you — a Private pilot, current, roughly 180 hours total. You did not apply carburetor heat during the run-up because the engine ran smoothly. You did not apply it after takeoff because you were focused on the climb and the engine sounded normal at that moment.

NTSB ERA25LA028 (2024): A Cessna 150H encountered carburetor ice at cruise altitude in conditions with 100% relative humidity and a temperature/dew point spread conducive to serious icing. The engine ran rough and lost power. The probable cause was carburetor ice formation in conditions conducive to serious icing, with the pilot's delayed use of carburetor heat. The pilot did not apply carb heat until after the power loss was obvious.

NTSB ANC25LA005 (2024): A Cessna 150 on initial climb experienced partial engine power loss due to carburetor ice in conditions with 70% relative humidity conducive to serious icing at glide power. The probable cause was the pilot's improper use of carburetor heat — the pilot applied it but then removed it, allowing the ice to reform.

NTSB ERA24LA087 (2024): A Cessna 150M on a solo cross-country instructional flight experienced partial engine power loss due to carburetor icing when the student pilot failed to apply carburetor heat. The pilot made a forced landing to a field and overran the runway. The probable cause was the pilot's failure to use carburetor heat in icing conditions.

NTSB CEN21LA381 (2021): A Cessna 150M experienced partial engine power loss due to carburetor icing during takeoff near Wadsworth, Ohio, when the pilot failed to apply carburetor heat despite conditions in the moderate-to-serious icing range. The pilot made a forced landing to a corn field where the aircraft nosed over.

NTSB ERA21LA284 (2021): A Cessna 150 instructional aircraft lost engine power during takeoff due to carburetor icing and made a forced landing into trees near Elba, Alabama. The probable cause was carburetor ice formation under atmospheric conditions conducive to serious icing at glide power, with contributing factors including insufficient time to melt accumulated ice despite carburetor heat application.

NTSB CEN23FA077 (2023, FATAL): A Cessna 150H on an instructional flight conducted a night visual approach to a non-towered airport in dark conditions. The aircraft descended below safe altitude and impacted a farm field 1.2 miles short of the runway. The probable cause was the flight instructor's failure to apply carburetor heat after a loss of engine power due to carburetor icing, combined with loss of control while maneuvering for forced landing in dark night visual meteorological conditions.

The real accidents cited above occurred at other airports and in other aircraft — NOT at Venice Municipal Airport. KVNC has its own accident history (see field dominant patterns), but these specific events happened elsewhere. The scenario is localized to KVNC to make the off-field environment real and consequential for you as a student here.

The consistent thread across all these events: carburetor ice in the C150M is insidious. It builds gradually, the first symptom is roughness and a dropping tachometer (not a dramatic power cut), and by the time it is obvious, it may be too late for a comfortable recovery. The fix — full carburetor heat, immediately, at the first sign of roughness in conducive conditions — is simple. The failure is always a delay or improper application.