The Cessna 172S VSO stall speed is 40 KIAS. Learn the model, weight and bank-angle caveats, and why VSO is not an approach speed.
For Aviation & Real-World Flying, the Cessna 172S has a VSO of 40 KIAS (47 KCAS) at 2,550 lb in the landing configuration. VSO is its power-off stall speed, or minimum steady flight speed, with landing flaps. Other C172 variants differ, so the exact aircraft’s POH takes precedence.
What does VSO mean on a Cessna 172?
VSO, pronounced “V-S-zero”, is the stall speed or minimum steady speed in the specified landing configuration. The zero refers to that landing configuration; on a standard fixed-gear Cessna 172S, the significant change is full landing flap.
| Speed basis | Published C172S VSO | What it represents |
|---|---|---|
| KIAS | 40 knots | The indicated speed shown to the pilot |
| KCAS | 47 knots | Indicated speed corrected for instrument and position error |
These figures describe the same stall condition, not two different versions of the aircraft. The large difference occurs because pitot-static position error becomes significant at the high angle of attack near a stall. On the standard 172S airspeed indicator, 40 KIAS is also the lower end of the white flap-operating arc.
VSO is not the stall-warning horn speed. The warning should sound before the actual stall, while the wing stalls only when it exceeds its critical angle of attack. Our explanation of the 172’s airspeed indicator, flaps and primary controls provides the cockpit context for recognising those cues.
Why is the stall not always exactly 40 knots?
Forty KIAS is a published reference condition, not a fixed speed at which every Cessna 172 wing will stall. The actual value changes with several factors:
- Aircraft model: Older 172 variants, different flap systems and approved modifications can have different published values.
- Weight: A lighter aircraft normally stalls more slowly. As an approximation,
new stall speed ≈ published stall speed × √(new weight ÷ published weight). Use the same speed basis on both sides of the calculation. - Bank and load factor: A level 60-degree bank produces about 2g, raising stall speed by roughly 41%. A 40-knot reference therefore becomes about 57 knots under that load.
- Configuration: Partial or retracted flaps do not meet the VSO landing configuration. The familiar 48-KIAS clean figure for the 172S is VS1, not VSO.
- Centre of gravity and power: Forward centre of gravity generally raises stall speed, while power and propeller slipstream alter the indicated speed and handling at the break.
- Aircraft condition: Frost, ice, damaged surfaces or an unapproved configuration can raise the stall speed and change the warning signs.
An accelerated stall can therefore occur well above 40 KIAS. Watching airspeed alone does not prevent one; bank, back-pressure and angle of attack matter just as much.
Is VSO the correct Cessna 172 approach speed?
No. VSO is a stall reference, not the speed to hold on final approach.
For a 172S, normal full-flap approach speeds are typically well above 40 KIAS and must come from the applicable POH, loading and wind procedure. Our Cessna 172 landing-speed guidance explains the usual approach and touchdown ranges without confusing them with VSO.
Blindly multiplying VSO by 1.3 gives 52 KIAS, but that is not a substitute for the manufacturer’s published approach speed. Conversely, carrying a large arbitrary gust additive can produce excessive float and consume more runway.
How do you find the exact VSO for a particular 172?
Use the approved information for the specific model and configuration rather than copying a generic online figure.
- Identify the variant: Confirm whether the aircraft is a 172N, 172P, 172R, 172S or another version, including any relevant approved modifications.
- Check the POH: Read the airspeed-limitations section and the detailed stall-speed table. The table may separate flap setting, bank angle, weight and centre-of-gravity condition.
- Check the units: Do not interchange KIAS and KCAS. For the 172S, 40 KIAS and 47 KCAS are the same published VSO condition.
- Use the correct instrument: Read indicated airspeed, not GPS ground speed. Wind changes ground speed but does not directly change the wing’s aerodynamic stall speed.
How should VSO be checked in a flight simulator?
A well-modelled Cessna 172 should stall near its published figure only when weight, configuration, power and manoeuvre match the POH conditions.
- Match the aircraft: Select the precise 172 variant and set a known fuel and payload weight.
- Configure for VSO: Use full landing flap, power idle and wings approximately level at a safe simulated altitude.
- Reduce speed gradually: Hold altitude by increasing angle of attack and watch for the horn, buffet, control softness, sink or nose drop.
- Record the right value: Note indicated airspeed at the actual stall, not when the horn first sounds and not the GPS speed.
- Recover by reducing angle of attack: Add power and manage flap retraction according to the aircraft procedure; power alone does not unstall the wing.
Control calibration, aggressive pitch inputs and simplified add-on flight models can all distort the result. In a real aircraft, intentional stalls should be practised only with suitable training, adequate height and the approved checklist.