Spinning (mis)concepts

At 18:24 27 January 2004, Mike Lindsay wrote:

3) 'Always fly flatter close to the ground' - Now here
is one that REALLY
bothers me.
This is probably the WORST misconception that insists
in lingering around
hangar talk, internet talk and in other media with
many 'experts'.
It should be replaced with 'Always fly coordinated
!' or 'Fly with the right
amount of bank for the turn you want to make'.
That's the simple, naked, honest truth.

Instilling fear of banking close to the ground is one
of the worst things
you can do to your students.
I really hate people who insist on this one.
Gliders will not Stall or Spin due to bank angles.
They will do so because
of angle of attack (pitch) not angle of bank.
Since most of us don't have an AOA indicator in our
gliders, we use Speed as
an easy way to determine it.

OTOH if you do a well banked turn close to the ground
and there is a
steepish wind gradient, its liable to be the last one
you ever do.


If you are flying on a day that has a strong wind gradient,
surely you would actually have compensated for that
with a higher approach speed? I personally have never
had any problem with steeply banked, cordinated final
turns, even under conditions of severe turbulence or
rotor. Spin and stall avoidance is all about the speed
you have. I take it from your comment you have never
explored the stalling characteristics of any aircraft
you have flown under different angles of bank?

Then it may be a different matter if you are _just_
making it back
from a cross country and are so low that you might
hit the ground
with the wingtip. Though I have never been there myself
I have heard
about people making their final turn 'with the rudder'
in that
situation. I just wonder whether it would help at
all, since there'd
be quite a penalty in height for the unclean flying
involved.
(Apart from the fact that there will have been some
fairly poor
airmanship involved to end up in that situation
in the first place.)

CV



Hmmm, did'nt realise you could 'make a turn' with the
rudder!

Who ever the instructor is that taught this wonderful
technique, and who ever their CFI is that alow them
to continue to practice this technique, they both should
be sacked and banned from ever instructing again.

While there maybe secondary roll effects when you yaw
your glider, the whole purpose of the rudder is to
align the glider with the airflow. It is the ailerons
which instigate a turn by rolling the wings. The rudder
is used to 1) correct the adverse yaw 2) control any
slide or skid 3) align the airframe with the airflow
as you roll. The elevator is used to maintain a constant
speed through out.

If you chose to fly at or near the stall, and your
glider has a strong incipient spin characteristic,
it makes no odds whether you are turning or flying
straight and level.

Assume that if you touch that rudder near the stall
you will spin, and you will die!

First line of defence: Have sufficient airspeed and
fly coordinated when you are low.
Second line of defence: Be able to quickly recognise
and recover from an incipient spin.

Souldnt that be....
1) airspeed Airspeed AIRSPEED
2) ALWAYS fly coordinated
2) dont get low and try hard not to land out
3) dont fly so slow you have to worry about an incipient
spin

Geir Raudsandmoen om wrote:
I know at least one pilot who was saved from serious
injury or death by his ability to quickly recover from
an incipient spin at very low altitude (probably below
50 m). I watched it happen.

Woow! He must have experienced the fear of his life.


I am probably also in that category myself, having
once unintentionally started to spin a LS7 when flying
a very turbulent thermal close to a mountainside near
Orcierres in the Alps, and being saved by quick recovery
action.

Sure, ridge flying is one of the most spin prone activities
if one gets into the habit of flying too slow and too "flat".


As we are not perfect, we should try to have two (or
more) lines of defence whenever possible:
First line of defence: Have sufficient airspeed and
fly coordinated when you are low.
Second line of defence: Be able to quickly recognise
and recover from an incipient spin.

You are perfectly right.


Regarding the value of training fully developed spins:
I think the main benefits are to (hopefully) eliminate
the panic effect in a spin, and also to learn how to
avoid overspeeding or overstressing the sailplane in
the pull-out phase.

This is the point of concern to me. A lot of modern single
seater glasses don't like very much the pull-out phase, and
tend to take horrendous speeds in the dive. Hence my own opinion
to avoid as much as possible entering spin and if incipient spin
either appears, get out immediately. Of course on a good old
Ask13 one can play the game as much as one likes it. I seem to
remember examples where people *have* indeed overstressed glasses
in the pull-out phase, unfortunately for them.


--

Michel TALON

Arnold Pieper wrote:
Ok, Here is to Mike and CV. Apparently both of you aren't listening.

Hmmm. Surprising reaction, considering my post mainly supported your
views.

If you make a turn with just the rudder and the wings level or almost level,
in other words, an uncoordinated turn, close to the ground, THAT will be
your last turn.

If you don't have height abouve the ground enough to perform a coordinated
turn, you SHOULD NOT be turning.

Here's the bottom-line : THAT level turn with the rudder-only, performed at
10 or 15ft height, is what produces the first part of a Spin and results in
gliders hitting the ground with the nose and wingtip first, usually
crippling the pilot.
My gosh, you guys don't seem to get it, or read enough accident reports.

As Ian already pointed out I reported this as something that other
people claim to do, and I was in fact questioning it.

On the other hand your claim that any uncoordinated flying
automatically leads to a spin is just ridiculous. It rather
detracts from your credibility and otherwise sensible views.

And I must say, in all kindness, that you would benefit by trying
not to be so pompous. These discussions are much more interesting
and helpful if we can air our views and experiences on an equal
footing rather someone dishing out "bottom-lines" and "simple,
naked, honest truths" from their preacher's pulpit.

Cheers CV

we all know, from the accident statistics, just how
safe competition
pilots are, don't we?


Ian,

I am assuming you are being sarcastic? Where are you
getting your competition vs. normal flying accident
statistics from?

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

Owain

Geir Raudsandmoen wrote:
...
Regarding the value of
I think the main benefits are to (hopefully) eliminate
the panic effect in a spin, and also to learn how to
avoid overspeeding or overstressing the sailplane in
the pull-out phase. The pull-out is normally very different
after a fully developed spin vs. after the typical
quarter-turn incipient spin.


Maybe there is another benefit of training fully developed spins.
A pilot told me how this training and the way it was done saved
his life. The instructor who trained him insisted on practising
fully developed spins, with exit after a precise number of turns
in a precise direction, this varying with each exercise. Later
he was once ridge flying in front of a cliff when he has a spin
departure. He was about to attempt the recovery when he realized
that this would bring the glider just facing the cliff at exit
with no way to avoid crashing onto it, so he delayed this recovery
for a half turn as he was taught and made the exit in the proper
direction.

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

Arnold Pieper wrote:
Therefore, if you're maintaining the correct Speed in the traffic pattern,
you can (and SHOULD) bank the glider as appropriate for the turn. ALWAYS.
There is no exception.

A glider will not Stall/Spin from a coordinated turn with the proper speed.

This begs the question: a glider will NOT stall/spin from an
UNcoordinated turn with the proper speed, either.

It will do so always from an uncoordinated turn, usually with the Wings
close to level in a skidding turn and the stick aft.
Remember what I said about Wings level and the stick full aft.

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.

--
-----
change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

Geir Raudsandmoen om wrote:

I am probably also in that category myself, having
once unintentionally started to spin a LS7 when flying
a very turbulent thermal close to a mountainside near
Orcierres in the Alps, and being saved by quick recovery
action.

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...


As we are not perfect, we should try to have two (or
more) lines of defence whenever possible:
First line of defence: Have sufficient airspeed
and
fly coordinated when you are low.

OK, I've got to agree with PART of this, but in detail.
The US FAA Glider Flying Handbook, although it's nice to have
one, is edited poorly, in my opinion. It has a lot of different
definitions of a skid vs. slip, in different chapters
(clearly written by different people). The editor should
have seen this and standardized it.

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.
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.

Beyond this, I do a lot of training where the glider is
uncoordinated. Boxing the wake, slips (on the takeoff roll
and on landing), slack line recovery. I don't worry at
all because neither wing ever stalls.

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.
Think about a string on the end of a pole 20 feet long
at 45 degrees up from the nose. Would you want to use
this? Now let's make the wingspan really long and
put your CG back 4 inches, and leave your top of the
canopy yawstring in the same place. Now what happens?
With that high aspect ratio where the difference between
min sink angle-of-attack and stall is just a few degrees?

Now I assume I actually have a yawstring right at the CG instead.
I fly my Lingus with the 300 foot wingspan, which
stalls at 38 knots. I decide to put it into a
coordinated 60 degree bank, and fly at 53 knots. The
"G" chart says this is the correct speed, and the radius of turn
is 144 feet. Does anyone see anything wrong with this idea?
I certainly do. Some of the wing is actually flying
backwards. A glider with a 20 foot wingspan vs. a
300 foot wingspan is going to get a different result.
Even in coordinated flight, the wings are at different airspeeds.
Then I can just imagine the amount of opposite
aileron one would need...
Using the same "G" loading chart for airspeeds for
aircraft with different wingspans seems puzzling to me.

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.

So from my way of thinking, keeping the yaw string straight
and using the airspeed indicator are a poor man's way of
trying to keep either wing from stalling. Then
applying airspeed rules for bank with no consideration
for wingspan or aileron drag is another poor man's technique.


If I flew a nice schmancy L/D one billion glider with
long sexy wings, I'd invest in AOA indicators for each
wing (maybe halfway or more along).
I'd either rig them for worst case (worst flaps,
worst aileron deflection, worst spoilers) or I'd link
in the flap and aileron position info somehow.
The Beech Duchess has an stall horn/AOA indicator on
each wing (one side is for flaps up, the other for
flaps down), so this isn't entirely novel (although
it isn't specifically for spin avoidance).

An AOA indicator on each wing wouldn't be perfect
(bugs and ice and stuff still wouldn't get factored in),
but I'd sure like it Seriously, how much
drag would a couple of these cause?

Until then, I fly little short-wingspan things with
low aspect ratio and sacrifice performance. And I
use wide patterns, slow roll rates, excessive
airspeed, medium or less banks, and gentle control
inputs when close to the ground.

Second line of defence: Be able to quickly recognise
and recover from an incipient spin.

I'd say be able to quickly recognise and recover from
an incipient stall. Since I've not been able to
maintain a straight stall, I assume a stall = spin.
If I'm uncoordinated, it just happens faster.