Spinning (mis)concepts

(...............)
I've routinely stalled our club's Blanik from coordinated turns, and
other gliders, too. Establish a shallow banked turn (10-15 degrees,
say), then simply slow down while maintaining a coordinated turn. At
some point, the inner wing falls and the spin begins.

Coordination is important, but not sufficient to protect you from a spin.


Correct, coordination and speed will do.

If you banked a little more and kept flying coordinated you would at one
point reach the aft limit in the Stick travel and not be able to stall /
spin...

SNIP
I read in one of his notes that Carl Herold doesn't
ridge soar
any more, because he thinks it is too dangerous. After
I read
that, I had a little talk with myself about how close
I came to ridges a few times...

SNIP

I cannot recall his exact words, but the interpretation
of it that I came away with is-'If you are flying the
mountains of the western USA in strong summer conditions
there is no reason to get down that low. And if you
are that low you are asking for trouble.' IMHO that
makes a lot of sense.

With 1,000'/minute sink not uncommon in this terrain,
working nooks and crannies can bite hard. I have flown
with Carl, but cannot recall if we discussed this then.
Perhaps someone can refresh my memory, was this thought
of his from a forum or post?

What is coordinated? Well, if the yaw string or ball were
at the CG, and centered, that would be coordinated.

Center of pressure or aerodynamic center... but, yeah, right.

But
the string isn't. It is often in front of and higher than
the CG. When this is the case, at high roll rates,
and steep banks, keeping the yaw string
perfectly centered means I am in a skid.

I did some "back of the envelope" caculations, using nothing more than
high school trig and geometry and it's not as bad as you think.
Assumming a 45 degree banked turn at 55 kts, the turn radius is 240 feet
(source American Soaring Handbook). If the yaw string is 6 feet or so in
front of the center of pressure, the yaw string error, due to it's
position, is 1.4 degrees. Close enough, I think.

Tony V.

On Wed, 28 Jan 2004 19:25:52 GMT, "Arnold Pieper"
wrote:

(...............)
I've routinely stalled our club's Blanik from coordinated turns, and
other gliders, too. Establish a shallow banked turn (10-15 degrees,
say), then simply slow down while maintaining a coordinated turn. At
some point, the inner wing falls and the spin begins.

Coordination is important, but not sufficient to protect you from a spin.


Correct, coordination and speed will do.

If you banked a little more and kept flying coordinated you would at one
point reach the aft limit in the Stick travel and not be able to stall /
spin...


Please be very careful about this. Some gliders may not have enough
rudder authority under high load factors to achieve stall AOA but some
gliders are very happy to snap into a stall over the low wing in the
same circumstances.

On Wed, 28 Jan 2004 16:32:45 -0500, Todd Pattist
wrote:

(Mark James Boyd) wrote:

I think a slip is an uncoordinated manuever where both wings
are at the same airspeed. A skid is an uncoordinated
manuever where the wings are at different airspeeds.

A slip can occur while you are flying straight or while
turning. By definition, a skid can *only* occur in a turn.


Well, maybe so, but my understanding of a skid is a little
different. In my notion of a skid it is a flight condition in which
the amount of rudder applied is too great for the amount of bank
applied. Thus, in my thinking, if you are flying at zero bank -
not in a banked turn - ANY application of rudder will result in a
skid, not a slip.

Please let me know if I have this mixed up!

The wings are at different airspeeds in a turn regardless of
whether you are slipping, skidding or coordinated. They are
at the same airspeed in straight flight regardless of
whether you are slipping or coordinated. If you are
turning, and the airflow is coming across the fuselage from
the outside of the turn, you're in a skid. If it's coming
from the inside of the turn, you're in a slip.

Straight flight is a coordinated manuever where both
wings are at the same airspeed. Banked, turning flight is
a coordinated manuever where both wings are at
different airspeeds.



Todd Pattist - "WH" Ventus C
(Remove DONTSPAMME from address to email reply.)

What is coordinated? Well, if the yaw string or ball were
at the CG, and centered, that would be coordinated. But
the string isn't. It is often in front of and higher than
the CG. When this is the case, at high roll rates,
and steep banks, keeping the yaw string
perfectly centered means I am in a skid.

Humm, so we are all flying uncoordinated in a turn?

I couldn't pass this up, so I calculated how much the yaw string is
off. Assume a 300' turn radius, the yaw string is 5' ahead of the CG
and is 4" long. With these numbers the yaw string is off by 0.033
inch, much smaller than the diameter of the string itself!

Tom

Ian,

You have near enough admitted that you are extrapolating
information that clearly isnt there from the accident
reports. In my 15 years of reading S+G I have never
seen a 'Competition Pilots not in Competition accident
section'. Also accusing every comp pilot of not owning
up to incidents is just plain rubbish not to mention
insulting.

Please keep you amateur accident statistics thoughts
to yourself. You dont do anyone any favours including
yourself.

BTW. I have seen an early solo pilot 'Push on' which
resullted in a crash. Was he an aspiring comp pilot,
influenced by a comp pilot or did he just get it wrong?

Owain




At 17:36 28 January 2004, Ian Johnston wrote:
On Wed, 28 Jan 2004 12:37:49 UTC, Owain Walters
wrote:

: we all know, from the accident statistics, just how
: safe competition
: pilots are, don't we?
:
: I am assuming you are being sarcastic?

Yup.

: Where are you
: getting your competition vs. normal flying accident
: statistics from?

Reading the blood-and-gore pages of S&G

: I am interested because the vast majority of accident
: reports I read are nothing to do with competitions.

Well of course not. When you stuff up landing a glider
in a field
after pressing on, too late, too low and too tired,
you don't have to
compound things by owning up ...

Incidentally, note that I said 'competition pilots'
and not 'pilots
flying in competitions' ...

Ian

On Wed, 28 Jan 2004 19:25:52 GMT, "Arnold Pieper"
wrote:

(...............)
I've routinely stalled our club's Blanik from coordinated turns, and
other gliders, too. Establish a shallow banked turn (10-15 degrees,
say), then simply slow down while maintaining a coordinated turn. At
some point, the inner wing falls and the spin begins.

Coordination is important, but not sufficient to protect you from a spin.


Correct, coordination and speed will do.

If you banked a little more and kept flying coordinated you would at one
point reach the aft limit in the Stick travel and not be able to stall /
spin...


Please be very cautious about this. Some gliders may have
insufficient elevator authority to reach stall AOA under higher load
factors but this is not true of all gliders. Some do have the
elevator authority to very happily stall and fall off over the low
wing under higher load factors. The location of the Center of Gravity
in a particular flight influences this, but we still must be prepared
for stalls out of steep turns.

If you have zero bank, and apply rudder you will begin
a
flat turn.

Wrong! UTTERLY WRONG!!!! A rudder yaws the airframe,
it does not 'turn' or 'steer' the aircraft.

Your whole problem seems to be in compairing a glider
with a boat. They may both have rudders, but they both
do totally different things.

Next time you fly in your glider, line yourself up
with a straight feature. Apply some rudder to yaw the
glider, but keep the wings level. All you will do is
continue in a straight line, sideways on. (commonly
known as a side slip)

However, the rudder does has a secondary control effect,
which introduces a roll moment due to differences in
lift between the wings. (which is why the first thing
you do is apply full opposite rudder to counteract
the rotation in a spin)

It is the ailerons that instigate a turn, the rudder
is used in a coordinated manner to 1) check the adverse
yaw (secondary effect of ailerons), and 2) to align
the airframe correctly into the airflow.

Please stop using language which inforces a belief
that the rudder is used to turn a glider in flight.
Your very action in doing so may well end up enforcing
that belief into a low airtime pilot reading these
posts and KILLING THEM!

(Mark James Boyd) wrote in message news:401810d2$1@darkstar...

Now I go up in my glider, and I get in straight flight,
and I pull the stick back to the stop, and hold it
perfectly centered for about a minute. If the CG or design
don't allow a continual stall, the glider bucks up and down
in pitch. I try my best to keep it straight, but eventually
a wing drops, and it goes into a bucking spin/spiral.
If the CG or design allow a continued
stall, I try my best to keep it straight, and a wing drops,
and it goes into a spin. If I keep the stick all the way
back and centered, I can change the direction of the
spin with rudder (including a momentary straightness)
but can't keep it straight consistently.

The only aircraft I've been able to do a true full stall
straight falling leaf is in Cezzna 150/152/172s.
Washout, dihedral, huge vertical stab, huge rudder, CG hanging low.
I've never been able to do a straight ahead stall, stick back and
centered for a full minute, in any glider.



You haven't flown a SparrowHawk yet! Couldn't resist a short remark
here. You can even hold the stick full aft AND be fully cross
controlled through a number of pitch breaks in the SparrowHawk.

Doug Taylor