Rough Air Over Tsala Apopka
Carburetor ice, partial power loss, and a marginal climb — the C150's climb performance is already thin
The scenario
Departing Brooksville–Tampa Bay Regional Airport (KBKV), Brooksville, FL — Runway 09, climbing out on a 090° heading into a warm, humid Florida morning. Elevation 76 ft MSL; the runway is essentially at sea level.
It is late spring, 0930 local. OAT 26°C, dew point 21°C, altimeter 29.94. Scattered clouds at 3,500 ft, light rain shower two miles to the northeast. Visibility 9 SM. The humidity is high — 85% relative humidity — and the temperature/dew point spread is narrow. This is classic carburetor icing territory: the FAA icing probability chart marks this as 'serious icing at glide power, moderate icing at cruise power.'
You are 500 ft AGL, climbing through 68 KIAS (Vy, best rate of climb), heading 090°, when the engine begins to run rough. Power is noticeably down — the tachometer is dropping. The off-field environment ahead (to the east) is a mix of open developed land (parks, large lots), pasture, and medium development — not ideal, but workable. The airport is behind you. KBKV's tower is part-time (0700–2200) and is open; you are in Class D airspace.
Aircraft: Cessna 150M, solo, full fuel, 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 250 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 heads-down on the climb and the engine sounded fine at first.
- {'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. 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 the engine was already significantly degraded.
NTSB ANC25LA005 (2024): A Cessna 150 on initial climb experienced partial loss of engine power due to carburetor ice in conditions with 70% relative humidity conducive to serious icing at glide power. The pilot applied carburetor heat but improperly — cycling it on and off rather than leaving it on — which allowed the ice to reform.
NTSB ERA24LA087 (2024): A Cessna 150M student pilot on a solo cross-country flight failed to apply carburetor heat and experienced partial engine power loss due to carb icing. The student made a diversionary landing but touched down long, resulting in a runway excursion. The failure was twofold: no carb heat, and improper touchdown point management during the emergency landing.
NTSB CEN21LA381 (2021): A Cessna 150 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 pilot survived.
NTSB CEN23FA401 (2023, FATAL): A Cessna 150K on an instructional flight experienced partial engine power loss due to fuel system blockage and subsequently stalled during a descending left turn at low altitude. The flight instructor failed to maintain adequate airspeed after the power loss. The airplane exceeded its critical angle of attack and impacted terrain. The lesson: after a power loss, airspeed management is critical — do not let the airplane slow below best glide speed in an attempt to stretch the glide.
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, runway excursions, forced landings), 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 Florida 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, the decision window is measured in seconds — not minutes. The C150's marginal climb performance means a partial power loss at 500 ft AGL is already critical; every second counts.
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 20°C and 30°C when relative humidity is high — exactly the Florida 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 or cycling it on and off can worsen the situation by partially melting ice into water ingestion without fully clearing the restriction.
The C150's climb performance is marginal — a partial power loss at low altitude is critical.
The C150 at gross weight has a best rate of climb (Vy) of 68 KIAS and a climb rate of roughly 500 fpm at sea level in standard conditions. In heat, high humidity, or high density altitude, that climb rate drops significantly. A partial power loss at 500 ft AGL means you are already in a no-climb or descent situation. You do not have the luxury of time to diagnose and recover — every second counts. Best glide is 60 KIAS. If power is lost, establish 60 KIAS immediately and look for the best landing option ahead.
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 Florida summer departure, with OAT near 26°C and dew point near 21°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 500 ft AGL is waiting too long.
Built from the real accident record
Scenario built from NTSB ERA25LA028, ANC25LA005, ERA24LA087, WPR21LA329, CEN21LA381, ERA21LA284, CEN23FA401, CEN23FA077 — all C150-series carburetor ice and partial power loss events. Anonymized and localized to KBKV.
NTSB reports: ERA25LA028 · ANC25LA005 · ERA24LA087 · WPR21LA329 · CEN21LA381 · ERA21LA284 · CEN23FA401 · 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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