How Low to Spin??

http://groups.google.com/groups?hl=e...roup=rec.aviat
ion.soaring


Mark-

Just make sure to click the 'RAS only' bullet, and
use the standard google search techniques...


Well, we went over this last year. I don't know how
to look
up old RAS threads. Perhaps someone else does.
--

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

Lower, but not low. You can carry the same total energy
throughout the pattern.

9B

At 05:06 30 August 2004, Eric Greenwell wrote:

I can see how the 'fast' part can help, but not the
'low' part. Being low doesn't seem like an asset if
you are worried about stalls and spins.

Chris - always thoughtful and articulate - even when
pedantic. ;-)

Seriously, I agree with your point about avoidance
AND early, reflexive recovery to avoid a full-on spin.
I used to work on wing-drop recovery in an early S/N
Ventus A/16.6 - which had the most pronounced stall
break of any glider I can recall. The control input
was stick forward and into the turn plus top rudder.
It takes some practice to make it reflexive.

I recall the main reasons for teaching stabilized approach
are to provide a consistent visual reference for the
pilot and to keep from changing too many flight variables
at the same time. Honestly, I don't know how they
come up with recommended 'correct' pattern speeds -
nor how scientific or precise the algorithm. My assumption
is that the speed is picked as a tradeoff between stall
margin and approach energy - but that there is an acceptable
range. We regularly add 1/2 the wind speed - how exact
is that?

My personal experience is that it's quite easy to bleed
off 5-10 knots by accident in a moment of distraction,
but 15-20 knots takes longer and is more apparent.


9B


At 15:36 30 August 2004, Chris Ocallaghan wrote:
With the big spoilers on modern gliders, there's not
much risk in
adding 10 extra knots, and while your argument that
it adds an
increased cushion before stall is unarguable, I guess
the measure of
value comes in whether that reduced risk is a justified
departure from
the 'correct' pattern airspeed. I'm with Mark... it
deserves some more
discussion.

BTW, as I noted in another thread, spins are not caused
by lack of
airspeed, but uncoordinated use of the controls --
at least in modern
sailplanes. Two things must happen to enter a spin:
1) you must
stall, and 2) you must fail to apply sufficient rudder
during your
attempt to pick up the low wing with aileron. That
is, the sailplane
is designed with enough rudder to stop autorotation,
even with full
deflection of the aileron throughout the stall break.

As demonstrated by my thread last fall, a Ventus 2
won't spin if the
controls remain coordinated (half stick/half rudder...
full
stick/rudder). It enters a controlable spiral, instead.
However, half
rudder and full stick (or half stick and no rudder)
would induce a
spin if the stick is held full back throughout the
stall break.

Avoiding the stall is the first most important step,
but thorough
training of the appropriate response during an inadvertent
stall is a
close, close second. And I could even argue that it's
more important,
since once you've stalled by accident, the outcome
is determined by
how well you've been trained to recover (that is, it
becomes the
failsafe for your stall avoidance error).

Though I'm not a fan of axiomatic training, there's
some value in
remembering that you can stall at any attitude and
any speed. If you
wear that axiom on your sleeve, then you'd be best
served by
understanding and practicing superlative stall recovery
technique in
addition to practicing stall avoidance.

That so many capable pilots have stall/spun in relatively
docile
aircraft indicates to me that there is a training gap.
We are clearly
handling the controls diffently at low altitudes. Why?
If we can agree
that this is the case, then adding speed is good insurance.
But it
doesn't address the cause.

Andy, apologies for being the pedant. I'm spitting
this stuff out at
60 words per minute, so I'm not giving much thought
to 'balance.'

I'd always assumed there were two factors in choosing a pattern speed.
First, safety, thus the +5 for turbulence. The other was to place the
glider at best speed to fly. That way if you have to put the spoilers
away, you are guaranteed to cover the maximum distance. If I recall,
the simple formula for best speed was best l/d speed plus 1/2 the
headwind. Don't recall the second ever being explained though. Just
seemed to fit.

"Chris OCallaghan" wrote in message
om...
I'd always assumed there were two factors in choosing a pattern speed.
First, safety, thus the +5 for turbulence. The other was to place the
glider at best speed to fly. That way if you have to put the spoilers
away, you are guaranteed to cover the maximum distance. If I recall,
the simple formula for best speed was best l/d speed plus 1/2 the
headwind. Don't recall the second ever being explained though. Just
seemed to fit.

up to plus 15 knots is currently being taught around here

gust fronts and micro bursts make 30-50knot gusts relatively common during
summer afternoons here if there's over-development

two years ago we had a member landout in 70+mph cold front winds roaring in
from the north. in some places along the front the winds exceeded 90mph.
the pilot got about 8 miles in 7000ft to a landing about 4 miles south of
the gliderport. he stayed in the glider, flying it on the ground until
someone walked out and phoned for help.

at the time I was playing father/son softball with my boy scout troop about
30 miles southeast of the landout location. large chunks of trees started
flying by almost immediately as the winds hit

we knew the front was coming, but no clue of the strong conditions. we
usually expect some dust, but this was very different

frank whiteley
colorado

the simple formula for best speed was best l/d speed plus 1/2 the
headwind. Don't recall the second ever being explained though. Just
seemed to fit.

Not a formula but a rule of thumb that's pretty close - judging by a
number of polars I've looked at. The following article is very
simplistic but was written for a student who had trouble grasping the
concept of needing to stay upwind of the field in strong conditions:
http://home.comcast.net/~verhulst/GB.../headwind.html

Tony

In article ,
Chris OCallaghan wrote:
I'd always assumed there were two factors in choosing a pattern speed.
First, safety, thus the +5 for turbulence. The other was to place the
glider at best speed to fly. That way if you have to put the spoilers
away, you are guaranteed to cover the maximum distance. If I recall,
the simple formula for best speed was best l/d speed plus 1/2 the
headwind. Don't recall the second ever being explained though. Just
seemed to fit.

http://www.stolaf.edu/people/hansonr/soaring/spd2fly/

was really useful for me. It sort of drove home the
1/2 headwind idea as being close enough, and was useful for
deciding 30-45 deg of bank was fine for rope breaks.
But look at it yourself. Of course the 2-33 data is in
there, provided by yours truly

--

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

At 14:48 01 September 2004, Chip Bearden wrote:
There's a somewhat separate question of what the right
contents for
the procedures and checklists should be!

With apologies to pilots whose memories never fail
even under stress,
I'm one of those guys who does use a very detailed
written checklist.
Chewing gum isn't on it but things like food, drinking
water, reading
glasses, and landout jacket are. But I don't wait until
I'm #1 on the
takeoff line to use it.

etcetera


It's fun to scoff about obsessive/compulsive types
reaching for their
checklist and pencil during a spin recovery. But
I'll continue to
use my written checklist before every flight, as I
noted in the safety
talk I gave at this year's U.S. Standard Class Nationals.

Chip Bearden


At the World Gliding Championships many years ago,
I crewed for a guy who presented my fellow crewman
and I with a checklist containing 19 items regarding
the setting up of the glider ready for him to fly.
After about two days of practice we added two extra
items. #0 get rid of pilot, #20 ensure pilot in glider
before launching. We got on just fine after that (and
it was always just how he wanted it).

Could be. I think the approach speed in my flight manual
is several knots below best L/D. I'll have to double-check.
Of course at my home airport (Minden), there's hardly
ever less than 15 knots of wind in the afternoon...

...egads, maybe I'm flying too slow!!!

9B

At 18:24 01 September 2004, Chris Ocallaghan wrote:
I'd always assumed there were two factors in choosing
a pattern speed.
First, safety, thus the +5 for turbulence. The other
was to place the
glider at best speed to fly. That way if you have to
put the spoilers
away, you are guaranteed to cover the maximum distance.
If I recall,
the simple formula for best speed was best l/d speed
plus 1/2 the
headwind. Don't recall the second ever being explained
though. Just
seemed to fit.

At 18:24 01 September 2004, Chris Ocallaghan wrote:
I'd always assumed there were two factors in choosing
a pattern speed.
First, safety, thus the +5 for turbulence. The other
was to place the
glider at best speed to fly. That way if you have to
put the spoilers
away, you are guaranteed to cover the maximum distance.
If I recall,
the simple formula for best speed was best l/d speed
plus 1/2 the
headwind. Don't recall the second ever being explained
though. Just
seemed to fit.

It appears that if you draw a tangent to your glider's
polar beginning, not at zero, but at any given headwind
speed, the line will touch the polar at a point that
is best L/D plus half that headwind.