Rough Climb Over Pasture
Carburetor ice in a marginal-climb airplane — early recognition and immediate action are the only margin
The scenario
Departing Brooksville–Tampa Bay Regional Airport (KBKV), Brooksville, FL — Runway 03, climbing out on a 026° heading. Elevation 76 ft MSL; the runway is essentially at sea level.
It is a humid Florida morning in late spring: OAT 24°C, dew point 19°C, altimeter 29.94. Scattered clouds at 2,800 ft, light rain shower visible two miles to the northeast. Visibility 9 SM. Classic Gulf Coast conditions — warm, moist, and exactly the environment the FAA icing probability chart marks as 'serious icing at glide power, moderate icing at cruise power.' Relative humidity is 78%.
You are 350 ft AGL, climbing through 68 KIAS (Vy, best rate of climb), heading 026°, when the engine begins to run rough. Power is noticeably down — the tachometer is dropping. The off-field environment ahead (northeast of the runway) is mostly pasture, hay fields, and open developed land — good forced-landing terrain. KBKV's tower is part-time (0700–2200) and is open; you are in Class D airspace.
Aircraft: Cessna 150M, solo, full fuel (18 gal usable), within limits. Carbureted 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 the engine sounded normal at full power.
- {'label': 'Field', 'value': 'KBKV · Brooksville–Tampa Bay'}
- {'label': 'Runways', 'value': '3/21 · 9/27'}
- {'label': 'Elevation', 'value': '76 ft'}
- {'label': 'Aircraft', 'value': 'C150'}
- {'label': 'Dominant phase', 'value': 'Landing / Cruise'}
The decision
Before we get into the decision tree — what do you already know about carburetor ice in the C150? (Pick all that apply; this records your baseline.)
What the record shows
What the NTSB files show
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, with the pilot's delayed use of carburetor heat as a contributing factor. 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 pilot applied carburetor heat but did so improperly (partial heat instead of full on), which worsened the situation. The probable cause was improper use of carburetor heat.
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 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. The probable cause was carburetor icing and the pilot's failure to apply carburetor heat.
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 probable cause was the partial loss of engine power due to carburetor icing.
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 accident was attributed to loss of engine power due to carburetor icing and the flight instructor's failure to apply carburetor heat. 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 accidents cited above occurred at other airports and in other aircraft — NOT at Brooksville–Tampa Bay Regional Airport. KBKV has its own accident history (hard landings, forced landings, runway excursions, loss of control on the ground), but these specific carburetor ice events happened elsewhere. The scenario is localized to KBKV 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 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.
Key lesson — In warm, moist Gulf Coast air, the C150's carbureted Continental O-200-A can accumulate serious carburetor ice even at cruise power and above-freezing temperatures. Apply full carburetor heat at the first sign of engine roughness or unexplained RPM loss. At low altitude over open fields, the decision window is measured in seconds — not minutes. Off Runway 03 at KBKV, the off-field environment is mostly pasture and hay fields — good forced-landing terrain. But the margin is thin. Early recognition and immediate action are the only buffer.
Debrief — teaching points
Carburetor ice forms in conditions you would not expect.
The FAA icing probability chart shows 'serious icing at glide power' at temperatures between roughly 15°C and 30°C when relative humidity is high — exactly the Gulf Coast morning conditions at KBKV. You do not need visible ice, freezing temperatures, or IMC. Warm, moist air at reduced power is the classic carb-ice environment. The C150's Continental O-200-A is carbureted; it has no alternate air system. Carburetor heat is the only tool.
The first symptom is subtle — a dropping tachometer and engine roughness.
In a fixed-pitch airplane like the C150, carburetor ice first shows as engine roughness and an unexplained RPM decrease. There is no dramatic power cut. Pilots who are not actively monitoring the tachometer miss the early warning. By the time the roughness is obvious, significant ice has accumulated. Scan the tachometer as part of your regular instrument scan, especially in conducive conditions.
Apply full carburetor heat — not partial — and expect an initial RPM drop.
When you apply carb heat to an iced carburetor, the RPM will drop further before it rises. This is expected and normal: the heat is melting ice and the resulting water is briefly disrupting combustion. Do not remove carb heat when the RPM drops — that is the heat working. Hold it full on. The RPM will recover as the ice clears, typically within 15–30 seconds depending on ice accumulation. Partial carb heat can worsen the situation by partially melting ice into water ingestion without fully clearing the restriction.
The C150 is a marginal-climb airplane — especially at gross weight in heat.
The C150 has only 100 hp and a light wing loading. At gross weight (1,600 lb), best rate of climb (Vy) is 68 KIAS and best angle of climb (Vx) is 60 KIAS. In high density altitude or with a partial power loss, climb performance degrades rapidly. At 350 ft AGL with a rough engine, you are already in a precarious position. Early recognition and immediate action are not optional — they are survival.
Off Runway 03 at KBKV, the off-field environment is mostly pasture and hay fields — good forced-landing terrain.
The NLCD ground cover off Runway 03's departure end (heading 026°) is mostly pasture/hay, open developed (parks/large lots), and medium development. This is good forced-landing terrain — no water, no dense trees, no mountains. If the engine fails on the Runway 03 departure and altitude is insufficient to return to the airport, a controlled forced landing in the available fields is the correct outcome. Best glide is 60 KIAS. Doors unlatched before touchdown. Master off just before impact. Flaps for slowest possible touchdown speed — impact energy rises with the square of speed.
Proactive carb heat use in conducive conditions is not optional.
The C150 POH and the FAA Pilot's Handbook of Aeronautical Knowledge both recommend applying carburetor heat when conditions are conducive to icing — before the symptom appears. In a Gulf Coast summer departure, with OAT near 24°C and dew point near 19°C, that means applying carb heat during the run-up check (and confirming the expected RPM drop, then recovery) and considering its use during climb in visible moisture or high humidity. Waiting for the roughness to appear at 350 ft AGL over pasture is waiting too long.
Built from the real accident record
Scenario built from NTSB ERA25LA028 (2024 C150H carburetor ice / delayed carb heat), ANC25LA005 (2024 C150 improper carb heat use), ERA24LA087 (2024 C150M student carb ice / runway excursion), WPR21LA329 (2021 C150D engine surge / carb ice), CEN21LA381 (2021 C150M carb ice takeoff / forced landing), ERA21LA284 (2021 C150 carb ice takeoff / impact), and CEN23FA077 (2023 fatal C150H night carb ice / loss of control). Anonymized and localized to KBKV.
NTSB reports: ERA25LA028 · ANC25LA005 · ERA24LA087 · WPR21LA329 · CEN21LA381 · ERA21LA284 · CEN23FA077
ACS tasks: PA.I.F — Weather Information · PA.I.G — Cross-Country Flight Planning · PA.IX.C — Emergency Approach and Landing · PA.I.H — Human Factors · PA.II.B — Engine Starting / Systems Preflight
Relevant FARs: §91.3 · §91.13 · §91.185
Step through the full decision tree, make the calls, and see where each choice leads — then debrief it with your CFI.
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