terry wrote in
:

On Feb 19, 1:00*pm, Dudley Henriques wrote:
terry wrote:
On Feb 19, 10:02 am, "Bob Gardner" wrote:
Back to basics. I have in my hand the POH for a 172Q. In section
5, Performance, there is a whole page of data on stall speed vs
bank angle
. For
example, at aeight of 2500 pounds with flaps up, indicated stall
speed
is 50
with wings level, 54 at a 30* bank angle, 59 at a 45* bank angle,
and 7
1 at
a 60 degree bank angle.

easier to remember a formula

the load increase in a bank by a factor of *1/ cos( AOB)

since lift required is proportional to Vsquared

to maintain level flight the lift must increase in a bank by
*square root of load

thus it follows the *stall speed in a level bank *must increase
over

the unbanked stall speed by

Square root ( 1 / cos (AOB) )
which will give the numbers you have quoted from the POH.

At 60 degrees the load is 2g *stall increase by root 2, *after that
the g's just take off. *75 degrees is 3.8g which is the limit of
the average lightie.
and a good reason why the timid types like Msx and me dont like
stretching the evelope too far.
Right Max?
Terry
PPL Downunder

I am struck with this irrepressible twitch of unbridled American
humor as I envision some poor CFI up here using this explanation to
explain things to Mrs average housewife as she attends ground school
preparing for the written.

As Lord Kelvin once said ( or something like this ) if you cannot
explain a thing with numbers, your knowledge is of a meagre and
unsatisfactory kind . Now I am not suggesting for one minute that your
knowledge is unsatisfactory Dudley, I am sure you know the physics
better than me, but up to a point I think there is a lot of truth
in what Kelvin meant. Whilst I certainly dont advocate quantum
mechanics or Tucker equations, where you can explain something with
high school level maths or physics I believe this should be done. .
There are many things about flying which are extremely difficult to
fully explain with maths and physics, but banking at constant altitude
is not one of them.

The poster wants to know what effect banking has on stall speed.



Yes, but his question was phrased in such a way as to require an
explanation from first principles.
The math is incidental and not of a lot of use in flight.
However, the formula for acceleration vs stall speed is to multiply the
stall speed by the sq root of the acceleration. Assuming a constant
altitude is kept, a bank angle of 60 deg wil give 2 G the square root of
which is approximately 1.4. SO an airplane that stalls at 50 will stall
at 70 in a 60 degree bank. about 85 in a 70 (2.9 G) about 120 in an 80
deg bank (almost 6 G) and so on.
A 30 degree bank (about 1.15G) will increase the stall speed by about
1.07.
Call it 1.1 to take in to account the vagueries of aircraft handling..


Bertie