Polar with spoilers extended?

I am working though some calculations and need the sink rate as a
function of speed with the spoilers fully extended. Does anyone know
of such data for a glider? How do spoilers extended affect sink rate
as a function of speed?

Thanks,

Tim

Tim,
I have flown with you, why do you want to know this information? You
take off, fly far and fast and land when your glider touches the
ground. I don't ever remember you "using" spoilers...

Tom
Idaho
On Oct 21, 1:23 am, Tim Taylor wrote:
I am working though some calculations and need the sink rate as a
function of speed with the spoilers fully extended. Does anyone know
of such data for a glider? How do spoilers extended affect sink rate
as a function of speed?

Thanks,

Tim

On Oct 21, 10:50 am, " wrote:
Tim,
I have flown with you, why do you want to know this information? You
take off, fly far and fast and land when your glider touches the
ground. I don't ever remember you "using" spoilers...


Tom,

LOL, thanks. It is purely an academic exercise from a safety
discussion we had about what are the best steps to follow if you are
high on final. I am trying to look at the difference between several
suggested techniques if full spoilers are not enough.

My list of preferences is:
1. Full spoilers
2. add forward slip
3. add "S" turns

I have used the technique of slowing down to minimize forward speed,
increase sink and decrease glide angle. Others have suggested
increasing speed to increase drag. I am not a big fan of this
technique because I feel it minimizes options for the pilot and is
susceptible to pilot error that can end up in over shooting the LZ.
Last years article in soaring I believe confirms my feeling that this
is a technique that should not be held up as one of the primary
techniques that should be used. I am working on developing models to
asses each in terms of effectiveness, time required, safety and
options left to the pilot.

Tim

On Oct 21, 11:13 am, Tim Taylor wrote:
On Oct 21, 10:50 am, " wrote:

Tim,
I have flown with you, why do you want to know this information? You
take off, fly far and fast and land when your glider touches the
ground. I don't ever remember you "using" spoilers...

Tom,

LOL, thanks. It is purely an academic exercise from a safety
discussion we had about what are the best steps to follow if you are
high on final. I am trying to look at the difference between several
suggested techniques if full spoilers are not enough.

My list of preferences is:
1. Full spoilers
2. add forward slip
3. add "S" turns

I have used the technique of slowing down to minimize forward speed,
increase sink and decrease glide angle. Others have suggested
increasing speed to increase drag. I am not a big fan of this
technique because I feel it minimizes options for the pilot and is
susceptible to pilot error that can end up in over shooting the LZ.
Last years article in soaring I believe confirms my feeling that this
is a technique that should not be held up as one of the primary
techniques that should be used. I am working on developing models to
asses each in terms of effectiveness, time required, safety and
options left to the pilot.

Tim

If you are THAT much too high, wouldn't it also be prudent to consider
a large 360? It may not be pretty, but let's face it, if you have
turned final and just THEN realized you're way too high, you've
already lost all your style points.

360 on final?

Mmhhhh.... Two things come to mind:

- What if there are traffic in the pattern?
- What if at the end of your 360, you end up too low?

I like Tim's list better, and in fact, this is what I teach with
students.

PS: and if you are in a Janus, pop the chute!...:-)

Richard
Phoenix, AZ

I have used the technique of slowing down to minimize forward speed,
increase sink and decrease glide angle.

Yuck! Shudder! Surely you're just joking.

Others have suggested
increasing speed to increase drag. I am not a big fan of this
technique because I feel it minimizes options for the pilot and is
susceptible to pilot error that can end up in over shooting the LZ.

I didn't think so either until Marty Eiler at Cal City demonstrated it
for me as part of a BFR. Practiced, and properly done, it can produce
an unbelievably steep angle from decision point to stopping point. Yes
you have to point the nose at the ground and look temporarily like
you'll undershoot. Definitely not for beginners, but not a maneuver to
be dismissed either.

A suggestion: I bought a copy of the condor flight simulator a while
ago, in part to explore on the ground how things like this work out.
It does let you practice and explore limits of glider abilities. You
can find out, for example, exactly how much altitude a 360 will take
in various configurations, or how much altitude you really need for a
180 back to the airport.

John Cochrane

On Oct 22, 11:30 am, BB wrote:
Others have suggested
increasing speed to increase drag. I am not a big fan of this
technique because I feel it minimizes options for the pilot and is
susceptible to pilot error that can end up in over shooting the LZ.

I didn't think so either until Marty Eiler at Cal City demonstrated it
for me as part of a BFR. Practiced, and properly done, it can produce
an unbelievably steep angle from decision point to stopping point. Yes
you have to point the nose at the ground and look temporarily like
you'll undershoot. Definitely not for beginners, but not a maneuver to
be dismissed either.

A suggestion: I bought a copy of the condor flight simulator a while
ago, in part to explore on the ground how things like this work out.
It does let you practice and explore limits of glider abilities. You
can find out, for example, exactly how much altitude a 360 will take
in various configurations, or how much altitude you really need for a
180 back to the airport.

John Cochrane

Doing these tests in the actual glider (at high altitude) with a data
logger will produce reliable numbers. The simulator might or might
not reproduce the performance accurately enough.

Todd Smith
3S

On Oct 22, 2:57 pm, wrote:
On Oct 21, 11:13 am, Tim Taylor wrote:



On Oct 21, 10:50 am, " wrote:

Tim,
I have flown with you, why do you want to know this information? You
take off, fly far and fast and land when your glider touches the
ground. I don't ever remember you "using" spoilers...

Tom,

LOL, thanks. It is purely an academic exercise from a safety
discussion we had about what are the best steps to follow if you are
high on final. I am trying to look at the difference between several
suggested techniques if full spoilers are not enough.

My list of preferences is:
1. Full spoilers
2. add forward slip
3. add "S" turns

I have used the technique of slowing down to minimize forward speed,
increase sink and decrease glide angle. Others have suggested
increasing speed to increase drag. I am not a big fan of this
technique because I feel it minimizes options for the pilot and is
susceptible to pilot error that can end up in over shooting the LZ.
Last years article in soaring I believe confirms my feeling that this
is a technique that should not be held up as one of the primary
techniques that should be used. I am working on developing models to
asses each in terms of effectiveness, time required, safety and
options left to the pilot.

Tim

If you are THAT much too high, wouldn't it also be prudent to consider
a large 360? It may not be pretty, but let's face it, if you have
turned final and just THEN realized you're way too high, you've
already lost all your style points.

I only did a 360 once (my first solo landing in a high-performance
glass ship). I lost sight of the runway turning and ended up in a
worse position than if I had just continued.

These days, if I find myself a bit high, I apply full spoilers and
increase speed. If that's not enough, I add slip. Drag goes up at
least as the square of speed. I've never had a problem slowing down.

Mike

Frightening! That you would slow down to decrease
forward motion. What happens with downdrafts or wind
shear after you have given up the option for altitude
that speed gives you.

Forward slip in glass gliders won't get you much descent;
S-turns might eat up a good bit, but the high-parasitic
drag approach is a much more valuable tool.

Get about 4000ft agl near the pattern, open full spoilers,
and push over to about 70-80kts. When you've burnt
off 1000ft, lift the nose to the horizon until speed
drops to best l/d and then close the spoilers. You
will see that this is not a ballistic maneuver and
that it is completely controllable. I'm not sure a
speed curve for full divebrakes is needed; you can
eyeball this and make it come out right. Either find
an instructor who can demonstrate for you, or else
do it several times at altitude and when comfortable
practice it at lower altitude and on final. In the
latter situation you might do just a few seconds to
see how entry and recovery look and behave. There
is more probability of undershooting than overshooting,
in my experience, but you'll be aware that these are
about to happen before they become a serious problem.

I do these on BFRs routinely into a 2400ft strip.
Remember, you can break this off at any time, so you
don't have to give up options.


At 18:18 21 October 2007, Tim Taylor wrote:

LOL, thanks. It is purely an academic exercise from
a safety
discussion we had about what are the best steps to
follow if you are
high on final. I am trying to look at the difference
between several
suggested techniques if full spoilers are not enough.

My list of preferences is:
1. Full spoilers
2. add forward slip
3. add 'S' turns

I have used the technique of slowing down to minimize
forward speed,
increase sink and decrease glide angle. Others have
suggested
increasing speed to increase drag. I am not a big
fan of this
technique because I feel it minimizes options for the
pilot and is
susceptible to pilot error that can end up in over
shooting the LZ.
Last years article in soaring I believe confirms my
feeling that this
is a technique that should not be held up as one of
the primary
techniques that should be used. I am working on developing
models to
asses each in terms of effectiveness, time required,
safety and
options left to the pilot.

Tim