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

"jeplane" wrote in message
ups.com...
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.

And mine too, but things don't always go according to plan. I got into a
situation as a student pilot where I did a 360 on final. It was a case where I
had a brisk tailwind on my downwind leg combined with strong lift. In spite of
full deployment of the wimpy spoilers on my 2-33, I was climbing rather than
descending in the pattern.

As a more experienced pilot, I might have ventured downwind for a few seconds
making the pattern a non-event, but as a student pilot I rejected that option
due to fear of overdoing things in the brisk wind and landing short. I could
have added slip starting early on the downwind, but didn't even think of it at
the time and that opportunity was quickly behind me. We had recently been
practicing low rope breaks, so I did the math and figured out what a 360 (2
"rope break" 180-degree turns) would cost me and went ahead and did it whilst on
final. It worked out great, but my instructor was not pleased.

Vaughn

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.

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

Mike the Strike wrote:
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.

For whatever reason (I don't really want to start that flame war again,
although I think the mods to the DDX quietly prove the point), I've
found that the Duo Discus does not take kindly to excessive speed on
approach. There is no elegant way to bleed off the excess energy, you
end up either floating down the runway, or forcing it down hot and
jamming on the brakes. It is best to maintain a proper approach speed
with full dive brakes and slip or S-turn as needed. I've heard that the
Libelle behaves in a similar fashion...

Marc

On Oct 22, 7:57 am, wrote:
On Oct 21, 11:13 am, Tim Taylor wrote:
[snip]
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.

Was this a serious comment? How many more people have to die to prove
you should not be suggesting turning away from the runway? A pilot was
killed in the Sierras in the last few years doing exactly this and we
had at least another major accident this year in the Sierras this year
with the same thing. It is on of the precursors to stall-spin
accidents, nasty scenarios like if unexpected lift cause the glider to
be high, the turn takes the glider out of lift, now you are going down
fast and pointing the wrong way. And low and the ground is coming up
at you, maybe I'll pull back more, push that foot to make the nose go
round, ugh, oh f!@#... Use S-turns, parasitic drag approaches, slips
etc. but don't turn away from the runway.

---

As for the high speed/paracitic drag approach Cindy Brinkner talked
about this at an SSA convention a few years ago. Maybe she has slides
available etc. I was suprised by the whispering amongst some people
in the audience about "ohh this is bad". I see it as a very useful
tool to have in your toolkit. I think Cindy's points were don't try it
by yourself - go take a ride with an knowledgeable instructor and that
in the hands of less experienced piltos in the right gliders this may
be a safer techqunique than slipping - I've seen pilots who have *no*
clue how to really slip to loose height, far too timid, nose just a
little off center - I have no idea if they were taught better and have
just forgotten or what.

Like Marc says the Duo tends to hold energy and makes this somewhat
less useful (but it still works, you do come down faster), but slips
work great in a Duo as compensation for not overly effective spoilers.
I was all set to demonstrate a parasitic drag approach in a Duo today
but the instructor doing the check ride thought a rope break would be
better :-(

Things are not black and white, I'd hope good pilots want to try out
different techniques, see what works best in different gliders and
situations and have the benefit of different tools at their disposal.

Darryl