Farley,

This post is more appropriate in the flight dynamics forum, however here is how to do what you want.

There are several A Vars that help: Note the SDK gives them as per radian etc but you can use per degree instead which I find easier to grasp.

**A**:**LINEAR CL ALPHA,per degree. **This is the slope of the air file Record 404/1545 lift coefficient in the region of 0 to 10 degrees. A typical value is 0.1 per degree.

**A**:**STALL ALPHA,degrees. **This is the angle that corresponds to the highest value of CL in the air file Record 404/1545 table, starting from the -180 end. If you had edited an existing 404 and it had a higher CL in the minus angle range than your peak around 15°, you will get a permanent stall warning.

**A**:**ZERO LIFT ALPHA,degrees.** This tells you where CL is zero in the Record and completes the picture.

Now, to work out stall speed you also need the wing area and air density and weight.

**A:WING AREA,Square feet**

A:AMBIENT DENSITY,Slugs per cubic feet

A:**TOTAL WEIGHT,Pounds**

The lift equation is L=CL*0.5*RHO*V^2*S

Where L= Lift, =TOTAL WEIGHT,Pounds in level flight

CL= STALL ALPHA*LINEAR CL ALPHA, for example 15*0.1 = 1.5

RHO= AMBIENT DENSITY,Slugs per cubic feet this is 0.002377 at sea level

S=WING AREA, Square feet

V=True Air Speed, feet per second.

This will give you the stall speed clean.

To get the stall speed with flaps you need the flap lift per radian coefficient from the air file CLdf. A typical value is 0.4. This means that you add 0.4 to the clean wing CL if you have 1.0 radians (57.3 degrees) of flap deflection. 30° flap would then give about 0.2 additional CL. That coefficient can be found in Record 1101 or 1539

I'll let you do the math now you have the data

Roy