Bob Moore wrote:
john smith wrote
The one item for the PA32-300 that would not follow the formula for
calculating the lift line was Va. The book shows it as 132 kias, but
the formula generates a speed of 103 kias for the intercept of the
3.8 load limit line.

When is 3.8g not 3.8g? When it is 4.5g or some other number.
Remember, 3.8g is a minimum figure for the normal category.
I have seen V-N diagrams for aircraft where the 3.8g line was
extended upward to accomodate the gust loading envelope at Vno.
Observe the gust envelope in the diagram at this web site:
http://adg.stanford.edu/aa241/structures/vn.html

Yes, where the lift line intercepts the 3.8 load limit line is Va. Some
V-n diagrams then show another linear lift line extending from the load
limit line to Vno linearly back down then back down to Vne line.

Va=(33*sqrt(wing loading)).
But for the PA32-300 this calculation yields 145 kias, higher than book
value, 132 kias.
Vno is 149 kias.

For other aircraft the formula and book values coincide, but for some
reason, the PA32-300 numbers do not.

I have been using this formula to generate the lift line:
n=(V/Vs)**2
then plotting n (y-axis, rise) against V (x-axis, run)

It is interesting to note that Piper does not allow any negative
maneuvers in the Normal catagory, on 3.8 positive.

Should read "... only 3.8 positive."