How Low to Spin??

Marc Ramsey wrote:
Mark James Boyd wrote:
Marc Ramsey wrote:

No, I'm saying (based on experience) it's a lot easier to let yourself
slip (well, actually skid) into a dangerous uncoordinated turn from a
shallow bank, than it is from a steeper bank.

Hmmm...this could be true. It may be that rudder authority is pretty
good at low speeds, and with light foot pressures. At higher speeds,
the foot pressure required to really change the airspeeds dramatically
on the wingtips may make skids less likely to happen by mistake.

If one believes uncoordinated flight is the sole cause of stall/spin/spiral
close to the ground, then only rudder is the culprit. I don't think
this is the case...

It is far safer to be in a properly
coordinated turn with a 40 to 50 degree bank angle. Every glider I've
ever flown gives a much better warning of impending departure in a tight
turn, plus the visual (nose above horizon) and physical (G forces
slacking off) cues are much more pronounced.

The US Glider Flying Handbook recommends medium banks in the
pattern, and 1/4 to 1/2 mile pattern legs (distance from runway).
I'm gonna stick with this myself.

And how many pilots did this save from a spin? How many pilots
have died because of spins from the 40-50 degree bank angle vs.
the shallow bank angle?

Most pilots die spinning on the base to final turn, and they almost
always manage to do it from a slow shallow turn, rather than a slow
steep turn.

Hmmm...you made me look at the accident reports again. A third
possibility came up. In some cases it seems that the glider may
have never fully stalled, but simply overbanked, and the pilot
didn't stop the overbanking tendency, and went into a steep
spiral nose down.

There were 11 fatal accidents in the pattern caused by stall/spin/spiral
since 1990. One, on Aug 10, 1996, was simply a C.G. to rearward.

Aug 12, 01 bank, stall/spin, downwind to base, tight pattern
Jan 28, 01 60 deg left bank, 45 down, but ailerons were right turn
Oct 4, 96 45 deg bank, 60 deg dive
Jul 31, 96 sharp left turn, then steep descent
Jun 29, 96 steep left turn, stall
Sep 14, 95 left turn, stall during 180 after contest
May 21, 94 steep right turn, then spin
May 3, 94 flat skidding downwind to base, two month old pilot license
May 12, 91 left turn to final, stall
Sep 2, 90 180 deg climbing 180 after contest

One flat skidding turn, the others were in a bank. At least one
looks like an aileron spin (this can be done with feet off the rudders
completely, but is very hard to time correctly). Several don't
look like spins at all, but overbanking that led to a steep spiral
close to the ground. In others, it seems possible the steep bank was
after the spin entry, perhaps not before it.

Eric pointed out that past 45 degrees, many gliders just don't
have enough elevator to stall. This may be true, but it seems
at least some of these were overbanking, a dragging aileron,
and steep spirals instead.


But, hey, we can agree to disagree, as long as we're not in the same
glider...

Well, for now anyway, I can't see myself doing steep banks in the
pattern. And since the FAA says so, I'm gonna teach no more than
medium banks, and mild or moderate roll rates. At the recommended
pattern size, I don't see why this isn't sufficient.

I think we all agree that low and slow is no way to have a
long life...we just disagree whether most of these accidents
are caused by bad rudder(I don't think so) or by
coarse application of dragging aileron/overbanking...
--

------------+
Mark Boyd
Avenal, California, USA

Eric Greenwell wrote:

I suggest the elevator authority isn't any greater on a faster glass
ship because there is no need for it. My experiences in a Blanik L13,
Ka-6e, Libelle h301, Std Cirrus, ASW 20C, and an ASH 26 E were the same:
they were much harder to stall at 30-35 degrees than 10 or 15, and I
couldn't stall them above 45 degrees. This is in coordinated circling
flight.

What do you weigh? In the 2-33 with 230# forward, we can't
make it stall even straight ahead without an accelerated pullup.
But alone at 160#, I can stall it, but just barely.

I'd like to see C.G. calculations on all the stall/spin accidents
the NTSB investigates. I'd be willing to bet this is a
huge factor.
--

------------+
Mark Boyd
Avenal, California, USA

Mark James Boyd wrote:
Well, for now anyway, I can't see myself doing steep banks in the
pattern. And since the FAA says so, I'm gonna teach no more than
medium banks, and mild or moderate roll rates. At the recommended
pattern size, I don't see why this isn't sufficient.

In my mind (for gliders), a shallow bank is anything less than 30
degrees, moderate/medium is 30 to 45, steep is 45 to 55, and from 55 on
up you're in aerobatic territory. I use moderate turns for patterns and
most thermals, and steep turns only when needed for thermals (almost
always down low). I simply reject the notion that one is in any way
"safer" by using shallow turns near the ground...

Marc

In article ,
Marc Ramsey wrote:
Mark James Boyd wrote:
Well, for now anyway, I can't see myself doing steep banks in the
pattern. And since the FAA says so, I'm gonna teach no more than
medium banks, and mild or moderate roll rates. At the recommended
pattern size, I don't see why this isn't sufficient.

In my mind (for gliders), a shallow bank is anything less than 30
degrees, moderate/medium is 30 to 45, steep is 45 to 55, and from 55 on
up you're in aerobatic territory. I use moderate turns for patterns and
most thermals, and steep turns only when needed for thermals (almost
always down low). I simply reject the notion that one is in any way
"safer" by using shallow turns near the ground...

I reread the posts, and I used a shallow bank in my case because of
a lack of horizon (in the mountains) and because I saw no point
banking more (and thereby increasing sink rate) unless it was to
better center a known thermal (which I didn't have at that point).

So I think we agree on everything except the use of steep turns
(over 45 of bank) down low in a thermal. And this is merely
dependent on your definition of "low." I imagine you, like
several other posters who have said the same thing, have a lot of time
in the glider you are flying, and are quite familiar with it's
airspeeds, control pressures, and have it loaded to a
consistent C.G. For you, 55 degree banks at 300 feet can
be precisely done, and successful.

For some of us with less currency and less practice in type,
this could be quite dangerous. Vertigo, inadvertent coarse use
of controls (including roll), imperfect centering technique,
visual illusions due to wind and movement of the ground,
different pressure feel caused by different gliders or
C.G.'s, etc. can make this more hazardous.

I think, for me, all of the things I've listed above are much more
critical at 45+ degrees of bank and 300 ft, than 20-30 degrees
of bank. So I am limited in the performance I can get out of
my flying, and won't feel competent to make a save at the
altitudes and bank angles you can. Perhaps with more experience
at steeper bank angles, this will change. It's just that
I seldom have exceeded 45 degrees of bank while coring any thermal
so far...perhaps I'll try some steeper banks next time...
--

------------+
Mark Boyd
Avenal, California, USA

Mark James Boyd wrote:
Eric Greenwell wrote:

I suggest the elevator authority isn't any greater on a faster glass
ship because there is no need for it. My experiences in a Blanik L13,
Ka-6e, Libelle h301, Std Cirrus, ASW 20C, and an ASH 26 E were the same:
they were much harder to stall at 30-35 degrees than 10 or 15, and I
couldn't stall them above 45 degrees. This is in coordinated circling
flight.


What do you weigh? In the 2-33 with 230# forward, we can't
make it stall even straight ahead without an accelerated pullup.
But alone at 160#, I can stall it, but just barely.

About 180 lbs with the parachute I'd wear in these gliders, but they
were all balanced to about 60-70% of CG range.

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

Eric Greenwell
Washington State
USA

Mark James Boyd wrote:
One flat skidding turn, the others were in a bank. At least one
looks like an aileron spin (this can be done with feet off the rudders
completely, but is very hard to time correctly). Several don't
look like spins at all, but overbanking that led to a steep spiral
close to the ground. In others, it seems possible the steep bank was
after the spin entry, perhaps not before it.

I've witnessed three stall/spin accidents over the years, two gliders
turning base to final, and one power plane during departure. At the
end, all of them looked like a steeply banked turn into the ground.
Most eyewitnesses, particularly non-pilots, aren't going to notice
anything is wrong until after the spin has started, at which point it
will look very much like an abnormally steep turn.

I've also been in a G103 that was about to depart into a spin from a low
shallow left turn after a botched low finish at a contest. I was PIC,
but a CFIG (!) in back was flying. I noticed things were getting a bit
quiet, the left wing was starting to drop, and the stick was moving
toward the right. I reflexively slammed the stick forward, which was
probably what prevented us from making like a cartwheel.

In most gliders (and there are exceptions), when you stall in a turn the
inner wing is going to start dropping. If you release back pressure at
this point, you'll be fine. But, the natural reaction of too many
pilots is to try to pick up the low wing with aileron, which increases
the angle of attack on the already stalled wing, increasing drag and
decreasing lift, resulting in more bank, until the nose drops and you're
spinning for real.

Marc

Mark James Boyd wrote:
For some of us with less currency and less practice in type,
this could be quite dangerous. Vertigo, inadvertent coarse use
of controls (including roll), imperfect centering technique,
visual illusions due to wind and movement of the ground,
different pressure feel caused by different gliders or
C.G.'s, etc. can make this more hazardous.

Well, I disagree, and I strongly believe that a well-trained glider
pilot, in any glider, low or high, should be every bit as comfortable
and safe (if not more so) in a 50 degree bank as in a 20 degree bank.

Marc

Putting spin behaviour of a modern glass ship in this general way is pure
nonsense. Spin behaviour is different for every model, and even a model with
and without winglets enters differently. I wouldn't think about 300ft
revoveries with a Ventus b, but on my 20 w/ winglets I would at least think
about it.
But as a general rule, I avoid flying ships in the mountains which depart
violently and use 500ft to recover.

--
Bert Willing

ASW20 "TW"


"Bruce Greeff" a écrit dans le message de
...

, but a modern glass glider with
elliptical lift distribution departs violently into a spin and does not
recover
in less than 500-600" (altitude loss after recovery is irrelevant)

So - my opinion is - the answer is always no, unless you have already put
yourself in the position where you are effectively already dead, and all
the
possible outcomes are no worse. Personally I would prefer to avoid getting
into
the situation in the first place...

In article 412c108b$1@darkstar,
(Mark James Boyd) wrote:

It is far safer to be in a properly
coordinated turn with a 40 to 50 degree bank angle. Every glider I've
ever flown gives a much better warning of impending departure in a tight
turn, plus the visual (nose above horizon) and physical (G forces
slacking off) cues are much more pronounced.

The US Glider Flying Handbook recommends medium banks in the
pattern, and 1/4 to 1/2 mile pattern legs (distance from runway).
I'm gonna stick with this myself.

Uhhh ... in a glider, 40 - 50 degrees *is* a medium bank. 30 or less is
shallow. 60 or more is steep.

--
Bruce | 41.1670S | \ spoken | -+-
Hoult | 174.8263E | /\ here. | ----------O----------

Bert Willing wrote:
Putting spin behaviour of a modern glass ship in this general way is pure
nonsense. Spin behaviour is different for every model, and even a model with
and without winglets enters differently. I wouldn't think about 300ft
revoveries with a Ventus b, but on my 20 w/ winglets I would at least think
about it.
But as a general rule, I avoid flying ships in the mountains which depart
violently and use 500ft to recover.

Sorry all - I was generalising, but even the ASW20 spins interestingly, and will
sometimes reverse it's spin direction instead of recovering if the pilot's
technique is poor. Under the right (wrong) conditions even a K13 will depart
violently.

My point is that you should have a very good idea of exactly how much height
your aircraft uses in a spin, including the half second or more it takes you to
realise you have lost it, for you to recover in. Not the absolute minimum, in a
factory perfect example in still conditions with a test pilot at the controls.
Winglets, repairs, control wear and slop and build variations all change the
behaviour.

I think if you set up a logger and tested you might be a little more
conservative close to the ground.