Stall Speed (Vₛ, Vₛ₀, Vₛ₁)

The regulatory definitions are short. Under 14 CFR § 1.2, Vₛ means the stalling speed or the minimum steady flight speed at which the airplane is controllable; Vₛ₀ is that speed in the landing configuration; Vₛ₁ is that speed obtained in a specified configuration. The rewritten 14 CFR § 23.2110 requires an applicant for certification to determine the stall speed, or the minimum steady flight speed, for each flight configuration used in normal operations — takeoff, climb, cruise, descent, approach and landing — accounting for the most adverse conditions, with power at idle or zero thrust for propulsion used primarily for thrust.

What students have to internalise is that a wing does not stall at a speed; it stalls at an angle of attack. The published stall speed is the speed at which that angle is reached in one particular set of conditions — wings level, one-g, a stated weight and configuration. Change any of those and the speed changes with them. Load factor is the sharpest lever: because stall speed rises with the square root of load factor, a 60-degree banked level turn pulls two g and raises the stall speed by roughly 41 percent. Weight moves it the same way, more slowly, and a forward centre of gravity raises it because the tail must carry more download.

This is why stall speed sits underneath so many other numbers. Vₐ is derived from it. Approach speeds are multiples of it. The stall-warning speed Vₛᴡ is set relative to it. A pilot who understands stall speed as a variable rather than a placard number is in a position to understand almost everything else on the airspeed indicator.

Almost every early training failure that ends badly — the base-to-final overshoot, the low-altitude steep turn, the go-around that gets slow — is a stall speed that moved and a pilot who was still flying the number from the handbook. That is exactly why FAA-S-ACS-7 lists, as a knowledge element for each stall Task, the relationship between angle of attack, airspeed, load factor, power setting, airplane weight and centre of gravity, airplane attitude, and yaw effects: the ACS is asking whether the applicant knows what moves the number, not whether they can recite it.

For a flight school, the teaching problem is that this is a ground-school concept whose consequences only land in the air. Schools that get it right tend to sequence the aerodynamics briefing immediately before the airborne stall lesson rather than weeks earlier, so the student sees the relationship demonstrated while the theory is still fresh.

Aviatize lets a school sequence a ground objective and the flight lesson that depends on it as linked items in the syllabus, so an instructor can see at booking time whether the aerodynamics briefing has actually been completed and signed before a stall lesson is flown. Grades against each objective are recorded per attempt, so a chief instructor reviewing a student's progress can tell whether stall recognition is genuinely improving or whether the same recovery error keeps recurring across lessons.