Fuel Tank Confusion on the Second Touch-and-Go
A 200-nm cross-country, two landings, and a fuel selector that was never switched — engine failure on the approach to landing
The scenario
Departing Brooksville–Tampa Bay Regional Airport (KBKV), Brooksville, FL — Runway 09, returning from a 200-nautical-mile cross-country flight to a nearby airport. Elevation 76 ft MSL. The field is towered (part-time, 0700–2200 local); you are in Class D airspace with Tampa Class B overlying at 6,000 ft MSL.
It is a warm Florida afternoon: OAT 31°C, altimeter 29.89, visibility 10 SM. You have completed one full-stop landing and are now on your second approach — a touch-and-go to practice the landing and immediate go-around. The runway is clear, the tower is active, and the approach is stable.
Aircraft: Cessna 172M, solo, 150 hp Lycoming O-320 (carbureted), fixed-pitch prop, fixed gear, fuel selector BOTH. You departed with full fuel (42.5 gallons usable). The cross-country flight burned roughly 20 gallons; you estimate 22–23 gallons remaining. The fuel gauges read roughly half-full on both tanks.
Pilot: you — a Private pilot, current, roughly 180 hours total. You have flown this airplane before but not extensively. You did not review the fuel selector position before the approach. You did not brief yourself on fuel tank capacity or switching intervals. The first landing went smoothly. You are now on short final for the touch-and-go.
At 400 ft AGL on short final to Runway 09, the engine begins to sputter. Power is dropping. The runway is ahead, but the engine is failing. You have seconds to decide.
- {'label': 'Field', 'value': 'KBKV · Brooksville–Tampa Bay'}
- {'label': 'Runways', 'value': '3/21 · 9/27'}
- {'label': 'Elevation', 'value': '76 ft'}
- {'label': 'Aircraft', 'value': 'C172M'}
- {'label': 'Dominant phase', 'value': 'Landing / Cruise'}
The decision
Before we get into the decision tree — what do you know about fuel management in the C172M? (Pick all that apply; this records your baseline.)
What the record shows
What the NTSB files show
NTSB CEN25LA355 (2025): A Cessna 172 lost engine power during a second touch-and-go landing after a 200-nautical-mile cross-country flight. The probable cause was the pilot's failure to switch fuel tanks despite adequate fuel remaining on board. The pilot had not switched tanks during the cross-country flight and did not confirm fuel selector position before the approach. One tank was depleted; the other had usable fuel. The engine quit from fuel starvation on short final.
NTSB ATL03FA142 (2003, fatal): A Cessna 172M on an instructional flight from Perry, Georgia experienced engine power loss shortly after takeoff due to water-contaminated fuel. The CFI's inadequate preflight inspection failed to detect water contamination. The engine quit, the pilot lost control, and the airplane collided with terrain. The probable cause was the CFI's failure to detect water-contaminated fuel during the preflight.
NTSB CEN24LA168 (2024): A Cessna 172M on an IFR flight experienced engine power loss due to carburetor icing during descent in night IMC. The pilot touched down on a building roof. The probable cause was delayed use of carburetor heat, which resulted in ice accumulation beyond the point where heat could restore full engine power.
NTSB ERA23LA141 (2023): A Cessna 172 on an instructional flight experienced total loss of engine power due to inadequate oil lubrication. The engine was 55 hours past its required 100-hour inspection. The pilot made a forced landing to a marsh. The probable cause was a total loss of engine power due to lack of oil lubrication.
Regional precedents (WPR24LA167, GAA19CA534, WPR12LA023, ERA17LA205) show a consistent pattern: fuel starvation from improper fuel tank selection, failure to switch tanks, or running a single tank to exhaustion. The common thread is inadequate fuel management planning and failure to confirm fuel selector position before descent and approach.
The real accidents cited above occurred at other airports and in other aircraft — NOT at Brooksville–Tampa Bay Regional Airport (KBKV). KBKV has its own accident history (hard landings, forced landings, runway excursions), but these specific fuel-starvation events happened elsewhere. The scenario is localized to KBKV to make the off-field environment real and the decision tree consequential for you as a student here.
The consistent thread across all these events: fuel mismanagement is a silent killer. The engine does not fail because of a mechanical defect — it fails because the pilot did not manage fuel correctly. The fixes are simple: (1) calculate fuel burn based on time and power, not gauges; (2) confirm fuel selector position before descent and approach; (3) verify actual fuel quantity visually before the flight and before descent; (4) apply carburetor heat proactively in conducive conditions; (5) drain the fuel sump during preflight to detect water contamination. None of these take more than a few minutes. All of them prevent engine failure.
Key lesson — Fuel mismanagement kills. The C172M has a 42.5-gallon fuel capacity; each main tank holds roughly 21 gallons. The fuel selector is BOTH — you do not switch tanks in flight. But you must calculate fuel burn, confirm fuel quantity before descent, and apply carburetor heat proactively in warm, moist conditions. On short final at 400 ft AGL, it is too late to troubleshoot fuel or carburetor ice. The decision to land safely is made during preflight and cruise — not on approach.
Debrief — teaching points
Fuel gauges in the C172M are notoriously inaccurate — trust your calculations, not the gauges.
The C172M's fuel gauges are mechanical (float-based) and prone to error, especially in turbulence or when the airplane is not level. A gauge reading 'half-full' may be optimistic. The correct procedure is to calculate fuel burn based on time and power setting (e.g., 8 gallons per hour at 65% power), not to trust the gauges. Before descent and approach, calculate remaining endurance: if you departed with 42.5 gallons and burned 20 gallons, you have 22.5 gallons remaining, which is roughly 2.8 hours at 8 GPH. Verify this by visually checking the fuel quantity in each tank (via sight glass or tank cap) before the flight and before descent. If the visual check does not match your calculation, investigate before continuing.
The C172M fuel selector is BOTH — you do not switch tanks in flight, but you must confirm its position before descent.
The C172M's fuel selector has only one position: BOTH. Fuel flows from both tanks simultaneously. There is no need to switch tanks in flight. However, you must confirm the fuel selector is on BOTH before engine start and before descent. A fuel selector accidentally left on OFF or in an intermediate position will cause fuel starvation despite adequate fuel on board. Make it a habit: before descent and approach, confirm the fuel selector is on BOTH. It takes 5 seconds and can prevent an engine failure.
Water-contaminated fuel is a preflight failure — drain the fuel sump every flight.
Water is denser than fuel and settles at the bottom of the fuel tanks. If water is present, it will be in the fuel sump (the lowest point in the fuel system). A thorough preflight includes draining the fuel sump: open the fuel sump drain valve (located on the belly of the airplane) and let a small amount of fuel flow into a clear container. If you see water (it will be cloudy or have a distinct layer), the fuel is contaminated. Do not fly. Drain the fuel system completely and refuel with clean fuel. This check takes 30 seconds and can prevent an engine failure from water ingestion.
Carburetor ice in the C172M requires proactive carb heat use — applying it on short final is too late.
The C172M's Lycoming O-320 is carbureted and susceptible to carburetor ice in warm, moist conditions. The FAA icing probability chart shows serious icing risk at glide power even at 20–30°C with high relative humidity. Applying carburetor heat on short final, when ice has already accumulated, may not restore power in time. The correct procedure is to apply carb heat proactively during descent and approach in conducive conditions (warm, humid air, reduced power). If you are descending through 2,000 ft in warm, moist air, apply carb heat and leave it on. The slight loss of power is acceptable; the prevention of ice accumulation is not.
Engine failure on short final is survivable — land on the runway or in the open field ahead, at best glide speed (65 KIAS).
If the engine fails on short final at 400 ft AGL, you have roughly 30–45 seconds before you must land. The off-field environment off Runway 09 at KBKV is mostly open developed land, pasture, and medium development — good forced-landing terrain. Land on the runway if you are lined up; if not, slip the airplane and aim for the open field. Maintain 65 KIAS best glide speed. A landing at best glide speed minimizes impact energy and maximizes survivability. Do not attempt a go-around if the engine has lost power — there is no power to climb. Land straight ahead.
The preflight is where fuel emergencies are prevented — not on approach.
A thorough preflight includes: (1) visually checking fuel quantity in each tank (via sight glass or tank cap), (2) draining the fuel sump to check for water contamination, (3) confirming the fuel selector is on BOTH, (4) calculating fuel burn and endurance based on time and power, and (5) confirming adequate fuel for the flight plus reserves. If any of these steps reveals a problem, do not fly. On approach, it is too late to troubleshoot fuel. The decision to land safely is made during preflight and cruise — not on short final.
Built from the real accident record
Scenario built from NTSB CEN25LA355 (2025 C172M fuel starvation on second touch-and-go after cross-country flight), ATL03FA142 (2003 C172M water-contaminated fuel / inadequate preflight), CEN24LA168 (2024 C172M carburetor icing / delayed carb heat), ERA23LA141 (2023 C172M oil starvation / 100-hour overdue), and regional fuel-mismanagement precedents WPR24LA167, GAA19CA534, WPR12LA023, ERA17LA205. Anonymized and localized to KBKV.
NTSB reports: ATL03FA142 · CEN25LA355 · CEN24LA168 · ERA23LA141 · WPR24LA167 · GAA19CA534 · WPR12LA023 · ERA17LA205
ACS tasks: PA.I.F — Weather Information · PA.I.G — Cross-Country Flight Planning · PA.II.A — Preflight Inspection · PA.II.B — Engine Starting / Systems Preflight · PA.III.A — Normal Takeoff and Climb · PA.III.C — Normal Approach and Landing · PA.IX.C — Emergency Approach and Landing · PA.I.H — Human Factors
Relevant FARs: §91.3 · §91.13 · §91.185 · §91.207
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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