How to use this calculator
- Enter reference stall speed. Use a published or measured stall speed.
- Enter reference weight. Use the weight tied to that reference speed.
- Enter actual weight. Use the loaded weight being checked.
- Read adjusted Vs. Treat the result as a screening estimate.
How it works
The calculator uses Vs_actual = Vs_ref x sqrt(W_actual / W_ref). Lower weight lowers stall speed when configuration and CLmax stay the same.
Continue with maneuvering speed, Va weight adjustment and approach speed.
Worked example
Verified against the live calculator
A 50 kt stall speed at 2,300 lb adjusted to 2,000 lb is 50 x sqrt(2000 / 2300) = 46.6 kt.
Frequently asked questions
How does stall speed change with weight?
For this screening relation, stall speed scales with the square root of actual weight divided by reference weight.
Can I use maximum gross weight as reference?
Use the weight tied to the published stall speed you are adjusting, often maximum gross weight.
Does this include flap or CG changes?
No. It assumes the same configuration and aerodynamic condition as the reference stall speed.
Is this the same relation used for Va weight changes?
It is the same square-root weight logic that underlies many Va weight-adjustment screens.
Method & assumptions
- Assumes the same aircraft configuration, CG range and maximum lift coefficient.
- Use approved aircraft data when it publishes a different value or method.