Descent to Final — The Airspeed Decay
A Cessna 150M in the pattern at Tampa International: base-to-final turn, marginal airspeed, and the critical angle of attack
The scenario
Departing Tampa International Airport (KTPA), Tampa, FL — Runway 19R, full-stop landing pattern. Elevation 26 ft MSL. It is a warm, humid afternoon in late July: OAT 32°C, dew point 24°C, altimeter 29.91. Scattered clouds at 3,500 ft, visibility 10 SM. Winds are gusting 12–18 knots from the northeast, with occasional stronger gusts. Density altitude is approximately 4,200 ft — the airplane will climb and accelerate as if it were at 4,200 ft elevation, not sea level.
You are a Private pilot with 180 total hours, 60 hours in the Cessna 150M. You have flown this pattern at KTPA a dozen times. Today you are conducting a local flight with a passenger — a friend who is not a pilot, 165 lbs. You are 155 lbs. The airplane is at gross weight (1,600 lbs). You have completed two full-stop landings and are on your third approach.
You are on base leg, heading 272° (reciprocal of Runway 19R's 092° magnetic heading), at 800 ft AGL. Airspeed is 75 KIAS. Flaps are at 20°. Power is 1,200 RPM (descent power). The runway is in sight, 1.5 nm ahead. The tower has cleared you to land. You are about to begin the turn to final.
Aircraft: Cessna 150M, two aboard at gross weight (1,600 lbs). Continental O-200-A, 100 hp, carbureted, fixed-pitch prop, fixed gear. Fuel selector on BOTH. Carburetor heat is OFF (you did not apply it on descent because the engine was running smoothly). Steam panel, vacuum-driven instruments.
Pilot: you — Private, current, 180 hours total, 60 in type. The last two landings were uneventful. You are comfortable in the pattern. You have not flown at high density altitude before; you did not calculate DA or brief its effects on climb and descent performance.
- {'label': 'Field', 'value': 'KTPA · Tampa'}
- {'label': 'Runways', 'value': '10/28 · 19L/01R · 19R/01L'}
- {'label': 'Elevation', 'value': '26 ft'}
- {'label': 'Aircraft', 'value': 'C150'}
- {'label': 'Dominant phase', 'value': 'Landing / Takeoff'}
The decision
Before we enter the decision tree — what do you know about stall risk in the Cessna 150M during the base-to-final turn? (Pick all that apply.)
What the record shows
What the NTSB files show
NTSB CEN23FA401 (2023): A Cessna 150K on an instructional flight practicing touch-and-go landings experienced partial engine power loss due to fuel system blockage. The flight instructor, attempting to manage the power loss, failed to maintain adequate airspeed during a descending turn at low altitude. The airplane stalled and impacted terrain. The probable cause was the instructor's failure to maintain adequate airspeed after the power loss, resulting in an aerodynamic stall at low altitude with insufficient altitude for recovery.
NTSB WPR18FA244 (2018): A Cessna 150 stalled during initial climb shortly after takeoff. The pilot had failed to properly configure the wing flaps for takeoff (flaps were left at 20° instead of 0°), and the high density altitude reduced climb performance. The pilot exceeded the critical angle of attack during climb and the airplane stalled. The probable cause was the pilot's exceedance of the critical angle of attack, with contributing factors including improper flap configuration and high density altitude.
NTSB FTW91DRG06 (1991, fatal): A Questair Venture experimental aircraft stalled during a base-to-final turn on a maintenance test flight. The pilot failed to maintain flying airspeed during the approach. The airplane impacted terrain. The probable cause was the pilot's failure to maintain adequate airspeed during the turn.
NTSB SEA07CA125 (2007): A Cessna 170B stalled during a base-to-final turn when the pilot allowed airspeed to become too low. The pilot attempted recovery but the aircraft impacted a field adjacent to the airport. The probable cause was the pilot's failure to maintain adequate airspeed during the turn.
NTSB CHI89DET01 (1988, fatal): A Volksplane VP-1 stalled while turning downwind with a nose-high attitude and slow airspeed. The airplane entered an incipient spin and struck the ground in an inverted attitude. The probable cause was a stall with insufficient altitude for recovery.
NTSB ERA10CA300 (2010): A Piper PA-18-135 stalled and entered a spin during a climbing right turn on final approach when the pilot attempted to perform a 360-degree turn per ATC spacing request. The probable cause was the pilot's failure to maintain adequate airspeed during the climbing turn.
The consistent thread: stalls in the base-to-final turn occur when pilots allow airspeed to decay below safe limits while maneuvering at low altitude. The Cessna 150, with its light wing loading, is particularly susceptible. Density altitude, gusty winds, and tight turns all accelerate the decay. At KTPA, the off-field environment off Runway 19R's departure end is dense development — medium and open developed areas. A stall and spin at 500 ft AGL leaves no altitude for recovery. The real accidents cited above occurred at other airports — NOT at KTPA. The scenario is localized to KTPA to make the off-field environment real and consequential for you as a student here.
The lesson: maintain a shallow bank (15° or less) during the base-to-final turn, monitor airspeed continuously, and be prepared to execute a go-around if airspeed decays below Vref (60 KIAS) or if the approach becomes unstable. In the C150 at gross weight in high density altitude, the margin between safe airspeed and stall is narrow. Respect it.
Key lesson — The base-to-final turn is where most low-altitude stalls occur. In the Cessna 150M, stall speed in landing configuration (flaps 40°) is 42 KIAS, but safe approach speed is Vref = 60 KIAS. A tight turn, a descending maneuver, or a gust can decay airspeed rapidly. At 500 ft AGL, there is no altitude to recover from a stall. Maintain a shallow bank (15° or less), monitor airspeed continuously, and execute a go-around if airspeed falls below 60 KIAS or the approach becomes unstable. High density altitude, gusty winds, and gross weight all reduce your margin. Know your limits.
Debrief — teaching points
Stall speed is true airspeed, not ground speed — density altitude does not change stall speed.
The Cessna 150M stalls at 42 KIAS (true airspeed) in landing configuration, regardless of density altitude. However, high density altitude reduces climb performance and increases ground speed for a given true airspeed. At KTPA on a warm, humid day, density altitude of 4,200 ft means the airplane performs as if it were at 4,200 ft elevation. Climb and acceleration are sluggish. But stall speed remains 42 KIAS TAS. The confusion often leads pilots to maintain lower true airspeed in high DA, thinking they have more margin — they do not. Maintain Vref (60 KIAS) or higher on approach, regardless of DA.
The base-to-final turn is the most dangerous turn in the pattern.
The base-to-final turn combines three stall risk factors: (1) low altitude (typically 300–600 ft AGL), (2) descending maneuver (which naturally decays airspeed), and (3) a turn (which increases load factor and stall speed). The NTSB data shows that stalls in the pattern occur almost exclusively on the base-to-final turn. Maintain a shallow bank (15° or less), monitor airspeed continuously, and be prepared to level the wings and lower the nose if airspeed decays. If airspeed falls below Vref (60 KIAS), execute a go-around.
A tight turn to final can be fatal — maintain a standard-rate turn (3° per second).
A standard-rate turn in the Cessna 150 at 75 KIAS is approximately 15° bank angle. A tighter turn (20–30° bank) increases load factor, which increases stall speed. In a 30° bank, stall speed increases by approximately 10%. At 42 KIAS clean, a 30° bank stall speed is approximately 46 KIAS. In landing configuration (flaps 40°), the stall speed in a 30° bank is approximately 47 KIAS — very close to the clean stall speed. The margin is gone. Maintain a shallow bank during the base-to-final turn, especially in gusty conditions or at high density altitude.
Airspeed decay in a turn is insidious — you must actively manage pitch and power.
In a descending turn, airspeed naturally decays because the vertical component of lift is reduced. To maintain altitude, pilots instinctively pull back on the yoke, which increases the angle of attack and accelerates the decay. The correct response is to shallow the bank, add power, or both. Monitor the airspeed indicator continuously during the base-to-final turn. If airspeed is decaying, take action immediately — do not wait for the stall warning horn.
The stall warning horn is a late warning — act before it sounds.
The stall warning horn in the Cessna 150 typically activates 5–10 knots above stall speed. If the horn sounds on final approach, you are already in a dangerous situation. The correct approach is to maintain Vref (60 KIAS) or higher throughout the approach, so the horn never sounds. If the horn does sound, the correct response is immediate: level the wings, lower the nose, and add power. Do not continue the maneuver that caused the warning.
A go-around after an unstable approach is always the right call.
If the approach becomes unstable — if airspeed decays below Vref, if the descent rate is too high, if the airplane is not aligned with the runway, or if you recover from a stall warning — the correct response is to execute a go-around. Advance the throttle to full power, level the wings, and pitch for climb. A go-around is not a failure; it is airmanship. The NTSB data shows that pilots who recognize an unstable approach and execute a go-around avoid the accidents that kill pilots who try to salvage a bad approach.
Built from the real accident record
Scenario built from NTSB CEN23FA401 (2023 C150K stall on descent after power loss), WPR18FA244 (2018 C150 stall on initial climb, flap misconfiguration), and base-to-final stall precedents FTW91DRG06 (1991 Questair stall base-to-final), SEA07CA125 (2007 C170B stall base-to-final), CHI89DET01 (1988 Volksplane stall downwind), ERA10CA300 (2010 PA-18 stall on climbing turn). Localized to KTPA.
NTSB reports: CEN23FA401 · WPR18FA244 · FTW91DRG06 · SEA07CA125 · CHI89DET01 · ERA10CA300
ACS tasks: PA.VII.A — Approach and Landing · PA.VII.B — Go-Around / Rejected Landing · PA.VIII.A — Stall Prevention · PA.VIII.B — Stall Recovery · PA.I.H — Human Factors
Relevant FARs: §91.3 · §91.13 · §91.117
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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