Rough Climb Out of Zephyrhills

Departing Zephyrhills Municipal Airport (KZPH), Zephyrhills, FL — Runway 01, climbing out on a 360° heading. Elevation 90 ft MSL. Non-towered field, Class G airspace; you are on CTAF 122.8.

It is a humid Florida morning in late spring: OAT 26°C, dew point 21°C, altimeter 29.94. Scattered clouds at 2,800 ft, light rain shower one mile to the northeast. Visibility 9 SM. The conditions are textbook for carburetor icing: high humidity, visible moisture, and temperature/dew point spread conducive to serious icing at glide power. The FAA icing probability chart marks this as 'serious icing risk at glide power, moderate icing at cruise power.'

You are 500 ft AGL, climbing through 68 KIAS (Vy for the C150M at sea level), heading 360°, when the engine begins to run rough. Power is noticeably down — the tachometer is dropping from cruise RPM. The C150M's Continental O-200 is carbureted; it has no alternate air system. Off Runway 01 (heading 360°), the off-field environment is good — mostly pasture, hay, and open developed areas (parks/large lots) with evergreen forest. But at 500 ft AGL with a rough engine, you are marginal on altitude and airspeed.

Aircraft: Cessna 150M, solo, full fuel (18 gal usable), within limits. Continental O-200-A, 100 hp, fixed-pitch prop, steam panel, fuel selector on BOTH. Nothing was written up; the airplane was airworthy at departure.

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 did not anticipate icing in these 'warm' conditions. The C150M's marginal climb performance — especially at gross weight in heat — means every knot of airspeed and every RPM matters. A partial power loss at 500 ft AGL in a C150 is a low-altitude emergency.

NTSB ERA25LA028 (2024): A Cessna 150H encountered carburetor ice at cruise altitude in conditions with 100% relative humidity and temperature/dew point spread conducive to serious icing. The engine ran rough and lost power. The probable cause was carburetor ice formation with the pilot's delayed use of carburetor heat. The pilot had not applied carburetor heat proactively in conditions that clearly warranted it.

NTSB ANC25LA005 (2024): A Cessna 150 on a personal flight experienced partial engine power loss due to carburetor ice during initial climb 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 while operating on Mogas in icing conditions — a reminder that carburetor heat must be applied FULL ON, not partial.

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 diversionary landing but failed to attain a proper touchdown point, resulting in a runway excursion. The lesson: apply carb heat at the first sign of roughness, and if a forced landing is necessary, aim for the center of the field.

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. The C150M's light wing loading and marginal climb performance make it particularly vulnerable to carb ice on takeoff.

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 accident resulted from carburetor ice formation under atmospheric conditions conducive to serious icing at glide power, with insufficient time to melt accumulated ice despite carburetor heat application. The lesson: apply carb heat proactively, not reactively.

NTSB CEN23FA077 (2023, FATAL): A Cessna 150H on an instructional flight conducted a night visual approach to a non-towered airport in dark conditions with no cultural lighting. 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 maintain control after a loss of engine power due to carburetor icing while maneuvering for forced landing in dark night visual meteorological conditions. The real accident occurred at a different airport — NOT at KZPH — but the lesson is clear: carburetor ice in the C150 is lethal if not recognized and treated immediately.

The local environment at KZPH makes this scenario realistic: Runway 01's departure end (heading 360°) has good off-field options — pasture, hay, and open development — suitable for a forced landing if the engine fails early in the climb. Runway 19's departure end (heading 180°) has marginal off-field options — mostly open developed areas and evergreen forest — also suitable for a forced landing. The C150M's 100 hp Continental O-200 has marginal climb performance, especially at gross weight in heat; a partial power loss at 500 ft AGL is a low-altitude emergency. Early recognition of carburetor ice and immediate full carb heat application is the difference between a clean departure and a forced landing.

The consistent thread across all these events: carburetor ice in the C150 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.