Va and turbulent air penetration speed.

"Dave S" wrote in message
.net...
Gary.. let me break this down simply for you..

Im not that familiar with Excel and PROGRAMMING it. I dont use Excel
except other than to plug numbers into existing apps and that is rare. I
just dont have that familiarity with it. Blance gave me what I needed.
It was about saving my time, not about my lack of understanding concepts
and practical application.

Dave, I apologize if I misinterpreted your request. If you knew that the
formula is Va times the square root of weight-divided-by-max-gross, but you
didn't know that the corresponding Excel expression is
Va*SQRT(weight/max_gross), then you did indeed understand the concepts, and
just needed a hand with the spreadsheet itself. (Note though that you did
incorrectly classify Vx and Vy among the "static", weight-independent
speeds, which contributed to my impression that the concepts themselves were
in question.)

I wasnt looking for approximations, pnemonics or handy dandy quick tools
that serve as memory aids for people who have trouble with math.

Well, here I think _you've_ misinterpreted _me_. The approximation I
suggested was not a mnemonic, and had nothing to do with having trouble with
math--unless you consider the inability to mentally calculate square roots
while flying a plane to consititute a math deficiency. :-) I regard that
approximation as an important tool that should be familiar to any good
pilot, so my suggesting it was in no way a put-down.

Anyway, I was honestly trying to be constructive. I apologize again if I
did not succeed.

--Gary

Please dont try to judge my comprehension and abilities because I made a
simple request for a simple answer that you werent able to fulfil.

paste
If anyone HAS or KNOWS (or has the formulas)how to do this in Excel
snip
thats exactly what I asked for.

So.. please dont render me "unsafe" because you cant pay attention to
detail.. ok?

And once again.. thank you Blanche and the others who were constructive.
Dave

Gary Drescher wrote:
"Dave S" wrote in message
.net...

Wonderful.. Thankyou Blanche... I only have to tweak the name of the
variable A6 to plug this in..

This was exactly what I was lookin for.
Dave


Dave, please forgive me for saying so, but if you found the statement
"the
speed is
proportionate to the square root of gross weight" to be unhelpful, but
Blanche's "full_va*SQRT(A6/full_weight)" is "exactly what you were
looking
for", then with all due respect, you do not understand the calculation
well
enough to base a life-or-death piloting decision on it. If you use the
Excel expression without understanding how to derive it yourself or why
it's
correct, you're essentially choosing a speed to keep your plane intact
by
delegating the decision to someone on Usenet whom you don't even know.
And
since you were also uninterested in a very close approximation (within
2%)
that lets you do the same calculation in your head, how are you going to
check whether your implementation of the formula contains a typo or
other
problem that results in the wrong answer?

I don't mean to be critical, but I implore you to be sure you understand
exactly why and how some of the V-speeds (Vs, Vs1, Vx, Vy, Va, Vl/d)
vary
with weight, and why others (Vfe, Vle, Vlo, Vno, Vne) do not, and how
the
relation translates into a mathematical expression. (The reference I
pointed to earlier contains a full explanation using nothing more
advanced
than high-school physics.)

Fly safely,
Gary


Blanche wrote:

For the type of aircraft your club will be flying, the formula in
Kershner will be adequate.

The formula in Excel is

full_va*SQRT(A6/full_weight)

where

full_va printed weight in the POH (usually at gross weight)
full_weight gross weight for aircraft (again, most recent W&B)
A6 column with weight for calculation

I fly a cherokee, so I have weights from 1800 (lightest load with
fuel and me and gear) to 2400 (gross weight) in column A.

And while you're calculating Va, the Glide speed can be done at
the same time since it's also weight-based:

full_glide*SQRT(A6/full_weight)

have fun!