Engine Roughness on the Runway 22 Departure
Partial power loss at 400 feet AGL over open water — carburetor ice, fuel starvation, or mechanical failure. The decision window is measured in seconds.
The scenario
Departing Peter O Knight Airport (KTPF), Tampa, FL — Runway 22, climbing out on a 217° heading. Elevation 8 ft MSL; the runway is essentially at sea level. Off Runway 22's departure end (heading 217°), the off-field environment is open water — Hillsborough Bay and the Gulf of Mexico approach. There is no alternate landing surface ahead.
It is a hazy Florida afternoon in late spring: OAT 29°C, dew point 23°C, altimeter 29.92. Scattered clouds at 2,800 ft, light rain shower two miles to the south. 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.' You are in Class G airspace (non-towered CTAF); the overlying Tampa Class B begins at 1,200 ft MSL.
You are 400 ft AGL, climbing through 68 KIAS (Vy, best rate of climb), heading 217°, when the engine begins to run rough. Power is noticeably down — the tachometer is dropping. The water of Hillsborough Bay fills the windscreen ahead. You are alone in the airplane, full fuel, within limits. Nothing was written up; the airplane was airworthy at departure.
Aircraft: Cessna 150M, solo, 1,450 lb all-up weight (well below the 1,600 lb gross). Continental O-200-A, 100 hp, carbureted, fixed-pitch prop, steam panel, fuel selector on BOTH. The 150 is marginal on climb performance even at sea level and full power — at 400 ft with partial power, you are not climbing anymore.
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 notice the first signs of roughness. The decision window is now measured in seconds.
- {'label': 'Field', 'value': 'KTPF · Peter O Knight'}
- {'label': 'Runways', 'value': '4/22 · 18/36'}
- {'label': 'Elevation', 'value': '8 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 engine roughness and carburetor ice in the C150? (Pick all that apply; this records your baseline.)
What the record shows
What the NTSB files show
NTSB CEN23FA401 (2023): A Cessna 150K on an instructional flight experienced partial engine power loss due to fuel system blockage during touch-and-go practice. The flight instructor failed to maintain adequate airspeed after the power loss, and the airplane stalled during a descending left turn at low altitude. The accident was fatal. The probable cause was fuel starvation caused by a fuel system blockage and the instructor's failure to maintain airspeed.
NTSB CEN23FA077 (2023): A Cessna 150H on an instructional night flight experienced a loss of engine power due to carburetor icing. The flight instructor failed to apply carburetor heat. The aircraft descended below safe altitude and impacted a farm field 1.2 miles short of the runway in dark night VFR conditions. The accident was fatal. The probable cause was the instructor's failure to maintain control after loss of engine power due to carburetor icing while maneuvering for a forced landing.
NTSB CEN17FA281 (2017): A Cessna 150F on a personal local flight conducted intentional low-altitude maneuvering over a lake when the engine sputtered and the aircraft lost control. The accident was fatal. The probable cause was the pilot's failure to maintain clearance from the lake during a low-level maneuver.
NTSB WPR09FA326 (2009): A Cessna 150 on a personal flight from Lake Tahoe Airport entered a spin seconds after takeoff at approximately 100 feet AGL and impacted adjacent terrain. The accident was fatal. The probable cause was a partial loss of engine power due to a malfunctioning carburetor and the pilot's failure to maintain adequate airspeed while maneuvering to return to the runway. High density altitude was a contributing factor.
NTSB ATL97LA099 (1997): A Cessna P210N on a personal flight experienced partial engine power loss during initial climbout and the pilot ditched in the Gulf of Mexico. The accident resulted from loss of engine power for undetermined reasons, with a fuel line found against the induction elbow during post-accident examination. The pilot survived the controlled ditching.
NTSB NYC03LA109 (2003): A Cessna 175A experienced a partial loss of engine power during initial climb and ditched in shallow water near Ocean City, New Jersey after the pilot was unable to maintain altitude for return to the airport. The accident resulted from a partial loss of engine power for undetermined reasons. The pilot survived.
NTSB BFO91LA069 (1991): A Cessna 177RG lost engine power at 300 feet AGL during initial climb and the pilot executed a controlled ditching in the Ohio River. The accident resulted from total loss of engine power for undetermined reasons, despite adequate fuel remaining on board. The pilot survived.
NTSB ANC13LA048 (2013): A Piper PA-16 on a personal flight from Shelter Island to Juneau experienced total engine failure shortly after takeoff at 350 feet AGL. The pilot successfully ditched the aircraft in the ocean; both occupants evacuated safely and were rescued.
The real accidents cited above occurred at other airports and in other aircraft — NOT at Peter O Knight Airport. KTPF has its own accident history (FORCED_LANDING 19.4%, LOSS_OF_CONTROL_INFLIGHT 16.7%, LOSS_OF_CONTROL_GROUND 11.1%, DITCHING 11.1%, STALL_SPIN 8.3%), but these specific events happened elsewhere. The scenario is localized to KTPF to make the off-field environment real and consequential for you as a student here.
The consistent thread across all these events: engine roughness or power loss in the C150 at low altitude is unforgiving. The first symptom is often subtle — a dropping tachometer, engine roughness — and by the time it is obvious, the decision window has closed. The C150 is marginal on climb performance even at full power; at partial power and low altitude, you are not climbing anymore. The fix — immediate full carburetor heat, or a decisive commitment to ditching — is simple. The failure is always a delay or a failure to maintain airspeed during the emergency maneuver.
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 water (off Runway 22, 18, or 36 at KTPF), the decision window is measured in seconds — not minutes. A delayed response means a ditching, not a field landing. If you commit to ditching, execute it decisively: 60 KIAS best glide, doors unlatched, master off before impact, flaps for slowest touchdown speed. Survival rates in controlled ditchings are significantly better than in uncontrolled ones.
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 KTPF. 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.
At KTPF, three of four runway departure ends are over water — ditching is a real outcome.
Off Runway 22 (217° heading), 18 (173° heading), and 36 (353° heading), the off-field environment is open water — Hillsborough Bay and the Gulf of Mexico approach. There is no alternate landing surface. If the engine quits on any of these departures and altitude is insufficient to return to the airport, the outcome is a ditching. Only Runway 04 (37° heading) departs over dense development — but even there, a low-altitude engine failure is a forced landing in a built-up area, not a field landing. Know your departure environment before you line up.
The C150 is marginal on climb performance — especially at partial power.
The C150M has only 100 hp and a best rate of climb (Vy) of 68 KIAS at sea level. At gross weight, in heat, or at high density altitude, climb performance is marginal. At partial power, you are not climbing anymore — you are maintaining altitude at best. At 400 ft AGL with partial power over water, you have no margin. Recognize this early and commit to a decision: either restore power (carb heat) or ditch. Do not try to stretch a glide to the runway from 400 ft with a sick engine.
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 29°C and dew point near 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 400 ft AGL over Hillsborough Bay is waiting too long.
Stall/spin is a real risk in a descending turn at low altitude with partial power.
The C150 is light and gust-sensitive. On a descending turn at low altitude with partial power, stall/spin is a real risk if airspeed drops below 60 KIAS. The NTSB CEN23FA401 and WPR09FA326 cases show that pilots who fail to maintain adequate airspeed during a low-altitude emergency maneuver stall the airplane and spin in. Maintain 60 KIAS (best glide) or faster during any low-altitude turn or approach. If you cannot maintain airspeed, ditch.
Built from the real accident record
Scenario built from NTSB CEN23FA401 (2023 C150K fuel starvation / stall), CEN23FA077 (2023 C150H carburetor ice / night approach), CEN17FA281 (2017 C150F low-altitude engine roughness), WPR09FA326 (2009 C150 carburetor malfunction / high density altitude), and regional ditching precedents ATL97LA099, NYC03LA109, BFO91LA069, ANC13LA048. Anonymized and localized to KTPF.
NTSB reports: CEN23FA401 · CEN23FA077 · CEN17FA281 · WPR09FA326 · ATL97LA099 · NYC03LA109 · BFO91LA069 · ANC13LA048
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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