Rough Climb Over Clearwater
Partial power loss on departure from a non-towered field — dense development surrounds you, and the decision window is measured in seconds
The scenario
Departing Clearwater Air Park (KCLW), Clearwater, FL — Runway 16, climbing out on a 155° heading. Elevation 71 ft MSL. Non-towered field (CTAF 122.8); you are in Class G airspace below 3,000 ft MSL. Above 3,000 ft MSL, you enter the overlying Tampa Class B airspace (ceiling 10,000 ft MSL).
It is a hazy Florida afternoon in late spring: OAT 29°C, dew point 23°C, altimeter 29.91. Scattered clouds at 2,800 ft, light rain shower two miles to the northeast. Visibility 7 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.' Off Runway 16's departure end (heading 155°), the off-field environment is poor: dense development, low-density development, medium development — no open fields, no water, no clear landing zones. You are climbing out over a built-up area.
You are 450 ft AGL, climbing through 73 KIAS (Vy), heading 155°, when the engine begins to run rough. Power is noticeably down — the tachometer is dropping. You are still over the departure area; the airport is behind you. KCLW is non-towered; you have no tower to advise. You are in Class G airspace.
Aircraft: Cessna 172N, solo, full fuel, within limits. Carbureted Lycoming O-320, fixed-pitch prop, steam panel, fuel selector on BOTH. Nothing was written up; the airplane was airworthy at departure. You completed a thorough preflight and run-up; the engine ran smoothly.
Pilot: you — a Private pilot, current, roughly 200 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 focused on the departure heading.
- {'label': 'Field', 'value': 'KCLW · Clearwater Air Park'}
- {'label': 'Runways', 'value': '16/34'}
- {'label': 'Elevation', 'value': '71 ft'}
- {'label': 'Aircraft', 'value': 'C172N'}
- {'label': 'Dominant phase', 'value': 'Landing / Approach'}
The decision
Before we get into the decision tree — what do you already know about partial engine power loss in the C172N? (Pick all that apply; this records your baseline.)
What the record shows
What the NTSB files show
NTSB CEN24LA362 (2024): A Cessna 172N encountered light rain and carburetor ice at 1,800 ft AGL. The engine ran rough and lost power. The probable cause was carburetor ice formation in conditions conducive to serious icing, with insufficient time and altitude for carburetor heat to clear the accumulated ice. The pilot had not applied carburetor heat proactively in conditions that clearly warranted it.
NTSB ANC26LA001 (2025): A Cessna 172 on an instructional flight experienced progressive engine power loss during training maneuvers despite carburetor heat application. The pilot made a forced landing on a road; the aircraft struck a rock during landing roll and nosed over. Atmospheric conditions indicated serious icing conditions in pressure-type carburetors — even with heat applied, the ice was too heavy to clear quickly.
NTSB CEN14LA374 (2014): A Cessna 172N on a personal local flight experienced partial engine power loss during cruise and made a forced landing to a cornfield. The accident resulted from partial loss of engine power due to failure of the dual magneto system caused by loose mounting screws, with improper maintenance during the annual inspection as a contributing factor. Not all partial power losses are carburetor ice — magneto failure, fuel contamination, and exhaust valve failure are also documented causes in the C172N fleet.
NTSB WPR15LA086 (2015): A Cessna 172N on an instructional flight over mountainous terrain experienced partial loss of engine power during a climb and made a forced landing into densely forested terrain. The reason for the partial loss of engine power could not be determined because the aircraft was not recovered from the remote accident site. The lesson: partial power loss can happen for reasons that are not immediately obvious — carb heat, mixture, fuel selector, and magneto checks are the standard diagnostics, but if none of them restore power, a forced landing is the correct outcome.
The real accidents cited above occurred at other airports and in other aircraft types — NOT at Clearwater Air Park. KCLW has its own accident history (see field dominant patterns: FORCED_LANDING 22.2%, LOSS_OF_CONTROL_INFLIGHT 18.5%, GEAR_UP_LANDING 18.5%), but these specific NTSB 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: partial engine power loss in the C172N 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. Off Runway 16 at KCLW, the off-field environment is dense development — a forced landing there is into buildings and streets, not open field. The decision window is measured in seconds.
Key lesson — In warm, moist Gulf Coast air, the C172N's carbureted O-320 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 development, 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 buildings and streets, not a field landing. Return to the airport immediately if power does not fully restore.
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 afternoon 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 C172N's Lycoming O-320 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 C172N, 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.
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 — buildings, streets, parking lots. There is no open field, no water, no clear landing zone. If the engine quits on the Runway 16 departure and altitude is insufficient to return to the airport, the outcome is a forced landing into the development. This is not a worst-case scenario; it is the geographic reality. Best glide is 65 KIAS. Doors unlatched before touchdown. 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.
Proactive carb heat use in conducive conditions is not optional.
The C172N 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 28–30°C and dew point near 22–23°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 450 ft AGL over development is waiting too long.
Built from the real accident record
Scenario built from NTSB CEN24LA362 (2024 C172N carburetor ice / power loss), CEN14LA276 (2014 C172N engine roughness / forced landing), ANC26LA001 (2025 C172N progressive power loss despite carb heat), CEN14LA374 (2014 C172N partial power loss / magneto failure), and WPR15LA086, WPR12LA306 (C172N partial power loss / forced landing). Localized to KCLW.
NTSB reports: CEN24LA362 · CEN14LA276 · ERA09LA517 · ANC26LA001 · WPR15LA086 · CEN14LA374 · WPR14LA099B · WPR12LA306
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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