Rough Climb Over Clearwater
Carburetor ice, marginal climb, and dense development off both runway ends — a C150 at gross weight in Gulf Coast heat
The scenario
Departing Clearwater Air Park (KCLW), Clearwater, FL — Runway 16, climbing out on a 155° heading. Elevation 71 ft MSL. Aircraft: Cessna 150M, two adults at gross weight (1,600 lb), full fuel, within limits. Engine: Continental O-200-A, 100 hp, carbureted. Fixed gear, fixed-pitch prop, steam panel, vacuum-driven instruments.
It is a warm, humid Florida morning in late spring: OAT 26°C, dew point 21°C, altimeter 29.92. Scattered clouds at 3,000 ft, light rain shower two miles to the northeast. Visibility 8 SM. The dew point spread is 5°C — classic Gulf Coast conditions. The FAA carburetor icing probability chart marks this as 'serious icing risk at glide power, moderate icing risk at cruise power.' The C150 at gross weight in these conditions has marginal climb performance to begin with.
You are 350 ft AGL, climbing through 68 KIAS (Vy, best rate of climb), heading 155°, when the engine begins to run rough. The tachometer is unwinding — RPM is dropping. The off-field environment off Runway 16's climb-out is dense development: low-density residential, medium development, scattered commercial. There is no open field, no park, no water. The developed area is the off-field option. KCLW is non-towered (CTAF); you are in Class G airspace. The overlying Tampa Class B begins at 3,000 ft MSL.
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 focused on the climb and the marginal performance — the C150 at gross weight in heat is not a climber. You are now at 350 ft AGL with a rough engine and no altitude cushion.
This is a decision-rich moment. You have roughly 20–30 seconds to diagnose and act before altitude becomes critical. The engine could be carburetor ice, fuel starvation, or a mechanical issue. The C150's 100 hp and marginal climb mean that any power loss at 350 ft AGL is serious.
- {'label': 'Field', 'value': 'KCLW · Clearwater Air Park'}
- {'label': 'Runways', 'value': '16/34'}
- {'label': 'Elevation', 'value': '71 ft'}
- {'label': 'Aircraft', 'value': 'C150'}
- {'label': 'Dominant phase', 'value': 'Landing / Approach'}
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 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 while operating in icing conditions.
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 improper use of carburetor heat while operating on Mogas in icing conditions.
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 accident resulted in a runway excursion during the diversionary landing.
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 pilot survived.
NTSB CEN23FA401 (2023, FATAL): A Cessna 150K on an instructional flight lost engine power 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, resulting in an aerodynamic stall at low altitude.
NTSB CEN23FA077 (2023, FATAL): A Cessna 150H on an instructional night approach lost engine power due to carburetor icing. The flight instructor failed to apply carburetor heat and subsequently failed to maintain control during forced-landing maneuvering in dark night VFR conditions.
The real accidents cited above occurred at other airports and in other aircraft — NOT at Clearwater Air Park. KCLW has its own accident history (forced landing 22.2%, loss of control 18.5%, gear-up landing 18.5%), but these specific events happened elsewhere. The scenario is localized to KCLW 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. The C150 at gross weight in Gulf Coast heat is already marginal on climb; any power loss at 350 ft AGL is critical.
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 in marginal climb conditions, the decision window is measured in seconds — not minutes. Off Runway 16 at KCLW, the off-field environment is dense development: a delayed response means a forced landing into houses and streets, not a field. The C150 at gross weight is not forgiving.
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 Gulf Coast morning conditions at KCLW. 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. A 5°C dew point spread (OAT 26°C, dew point 21°C) is a red flag.
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. At 350 ft AGL on the climb-out, you are not heads-down — you are watching the engine.
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.
At KCLW Runway 16, an engine failure on departure is a forced landing into development.
The off-field environment off Runway 16's departure end (heading 155°) is dense development: low-density residential, medium development, scattered commercial. There is no open field, no park, no water. A forced landing off Runway 16 means landing in or near houses and streets. This is not a worst-case scenario; it is the geographic reality. Best glide is 60 KIAS. Fuel selector BOTH, mixture rich, master off just before impact. Flaps for slowest possible touchdown speed — impact energy rises with the square of touchdown speed, so the slowest possible speed matters most. Know this before you line up on Runway 16.
The C150 at gross weight in Gulf Coast heat is a marginal climber.
The C150's 100 hp Continental O-200-A produces a best rate of climb (Vy) of 68 KIAS at sea level, but that climb rate deteriorates rapidly with temperature, density altitude, and weight. At gross weight (1,600 lb) in 26°C heat at KCLW (71 ft MSL), you are already marginal. Any power loss — even partial — is critical. A 50-RPM drop from carburetor ice at 350 ft AGL is not a minor annoyance; it is a life-or-death event. Recognize this limitation before you depart.
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 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 350 ft AGL over development 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 partial power loss / improper carb heat), ERA24LA087 (2024 C150M student failure to apply carb heat), WPR21LA329 (2021 C150D engine surge / delayed carb heat), CEN21LA381 (2021 C150M takeoff carb ice / forced landing), ERA21LA284 (2021 C150 takeoff carb ice / impact with trees), CEN23FA401 (2023 C150K fuel starvation / stall at low altitude), and CEN23FA077 (2023 C150H night approach / carb ice / loss of control). Anonymized and localized to KCLW.
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 · PA.II.C — Takeoff and Climb
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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