(Mark James Boyd) wrote in message news:412ce2c4$1@darkstar...

Some aircraft have a very nose low spin (Blanik), others have a much
flatter spin (Katana). The Katana, which spins very flat on the horizon,
is going North at 30 knots. I stall it and spin. Over the course of
a second, the nose is now pointed South. Is the Katana moving
South with an airspeed of 30 knots? No, it is not. This is
part of the reason why, during the first turn or two, the
pitch oscillates more violently than in a fully developed spin.

I still don't buy your explanation. A spin is a combination of roll,
pitch, and yaw, all happening at the same time. As a result, the
actual flight path (motion of the CG through space) is hard to see,
especially from inside the cockpit, but conservation of momentum
cannot be violated. From 30 knots, the first half turn/half roll
(which probably takes a bit more than one second, I would think) will
corkscrew the nose down and around, but you are not flying backward!
And until you are established is a steady spin, you will get pitch
motion due to the inclination of the spin axis to the horizon. Once
you are established in the spin, with your CG motion basically
straight down, the spin is usually pretty stabilized (with the usual
exceptions, including Maverick's F-14 spinning out to sea after
departing over the desert - I would have loved to have seen that for
real!)

It's normal for a power plane to spin flatter than a glider - more
weight in the nose (and probably tail) makes for more inertial weight
tending to level the fuselage.

Because of momentum, the airspeed from front to back of the
wings is less during the South pointed nose part of the spin than
during the entry of North.

Still a bad analogy, in my opinion. Think of the snap roll example -
at what point do you stop "rolling" and start "frisbeeing"? You
don't, your flightpath just curves more downward as you initiate the
spin slower.

It sure would be fun to take up a nice spinning glider (a 2-32 for
example), instument it, then take turns trying to make each other
sick!

And yes, this is a frisbee. At least for the first 180 anyway...

Nope. Although, look up Zurakowski Cartwheel - some testpilot used to
do 540 degree rotation hammerheads in a Gloster Meteor, long before
the current airshow acts started doing it in monster Pitts (which I
think are about as interesting to watch as a radio controlled model).
Not a stalled maneuver, though.

Ms. Campbell is the Hawaii state altitude record holder. She
worked at Dillingham as a CFI. She told me during a ground session
she was in an uncontrolled spin for more than 5,000 feet at one point,
with a passenger, before recovering.
She said after landing, she weighed the glider and the CG
was well aft of what was on the 10+ year old "official" form.
And her new calculated CG for that flight was well aft of limits.

Must have been in a 2-32. G

In my experience, the older the calculation, the further back
the actual CG is from it. Dirt and crap on the long lever arm
of the tail do a lot more than crap in the short nose.

Broken glass ships have the same problem with weight in the tail...
G-103s are notorious for it. Othewise, instruments, batteries,
cheeseburgers, and beer tend to move the CG forward.

Except for that 1 in 10 case, I'd guess aft CG is just a contributing
factor, not a cause. But I'd like to see data. When I hear of
a winch launch by an experienced pilot during the first
flight of the season, ending in a fatality, I have to wonder if
he took something out of the nose, or put something in the
tail, and so his stick pressure feel and initial trim setting
were off... Of the stall spin fatalities on record, I'd
bet most, if not all, had CG further back than the 60-70%
forward that Eric described...

Again, the aft CG doesn't cause the spin, it just make it easier to
initiate, and maybe harder to recover. You still have to exceed the
stalling AOA, regardless of CG location. Winch launching is probably
a lot safer overall than aerotowing (from my limited experience in
Germany), with fewer potential gotcha's - plus it's really hard to
kill the winch operator (unless you crash on the winch, of course).

Sounds like trying to turn via ground references down low - a big
no-no

This is required to fly a rectangular pattern with wind correction,
and still part of the PTS...

Not the same as max performance low altitude turning (thermalling),
which are definitely NOT ground reference maneuvers. Pattern turns,
on the otherhand, should always have enough airspeed to be safe - so
are not really "max performance" turns, and are usually no more than
90 - 100 degrees (unless you prefer the 180 degree one turn to final
approach, which I do).

Clearly true. If one weren't trying to land on a particular
bit of ground, and the world was just one big flat runway,
I'm certain landing accidents would be more rare.
Hard to quiz them, the dead are VERY quiet...

Well, most glider landing accidents only break the glider, or maybe a
bush or two - and the reasons are usually pretty consistent. The main
thread seems to be a certain rigidity in the pattern, reliance on
ground references and the altimeter for turns, and failure to engage
brain and remember to fly the plane.

Many of the 10 reports seem to indicate the spirals/spins happened
during the roll, not the turn. High roll rates require a lot of
rudder (and then rudder release), used quite precisely.

Again, AOA is the key. By itself, high roll rates shouldn't lead to a
spin. There is a situation where it can: Initiate a rapid roll after
a push-over from a steep climb to below stall speed. More of a winch
launch cable break scenario, and hard to duplicate while just flying
around, as it requires a transient airspeed below 1-G stall speed
(but at less than 1-G, so not stalled) then increasing the angle of
attack coupled with a lot of aileron. I've tried to get there in my
glider but haven't been sucessful yet.

I commonly induce vertigo in students to demonstrate unusual attitude
recovery. Although easiest to induce by rapid head movements,
I can also induce it with nothing more than a rapid, perfectly
coordinated roll into a steep bank, and then a rapid coordinated
roll to level flight. I've done this with pilots from 10-30,000 hours.
In all of them, if I cover all the instruments on a nice dark night
with foggles on, they get vertigo. Not staring at the ground and
avoiding rapid head movements is a start, but is an incomplete
solution...rapid roll rates and dramatic G changes are another
factor.

Not necessarily - the key is the lack of outside references, coupled
with moving the head too much so as to confuse the inner ear. Then
again, it is also person dependent - some people are very susceptible
to vertigo (and get sick during acro, or just thermalling), I think of
them as inner-ear dependent. Their bodies believe their inner ears,
not their eyes - not good in a plane. Other people are eye-dependent,
and could care less what their inner ear is saying, as long as they
have a good visual reference. I'm in the latter group, I can thermal
all day long and do acro and feel fine, but I have had the leans in
formation in cloud - interesting when you pop out and your internal
gyros cage up!

When I fly gliders, I have to remind myself to fly at least a 1/4 mile
out pattern. I normally fly a power plane (day VFR only) with a 5:1
glide ratio, and a tight pattern, with steeper banks and
faster roll rates at higher airspeed. I don't do this when
in a glider approaching an unmarked landout field with mountains and
no horizon around.

I fly my pattern based on where I want to touch down, and adjust the
pattern accoding to my altitude and the wind. I prefer low, tight,
fast patterns, so I can see what I'm getting into during a landout!
It helps that my glider can get rid of a lot of energy fast when I
need to.

I see we are agreeing again

On the whole, just a different interpretation of the same facts.

Kirk