Polar with spoilers extended?

On Oct 22, 3:33 pm, John Smith wrote:
Brian wrote:
Frightening? Really? It actually works very well with a bit of head
wind. Backcountry power pilots occasionally use this technique as
well.

It's a completely different thing in a power plane. (Although I wouldn't
recommend it with power planes, either.)

A short look at a typical glider polar is all that is needed to
understand why your "technique" is a no-no. If you continue using it,
then it's only a question of time that we'll hear about you in the news.

Looking at a polar is exactly why it works. It is called Speed to fly.
It really only works well when you have some headwind. It does work
somewhat in calm conditions but is really not very effective. It
probably doesn't work at all in a tailwind condition.

As noted gliders usually have a better ways of dealing with being
high. And since most people aren't excessivly high with a headwind it
does have limited use in gliders. There are really only two things
that can go wrong with using the technique and both should be easily
controllable. These are a Stall/Spin or continuing the slow approach
to too low of altitude to recover back to a normal approach speed.

Personally I seldom use it, The High Parasitic Drag approach and/or
Slips described above is usually more effective in a wider range of
conditions.

Brian

I first learned it in Minden and then refined it in
Cal City.

What the objecters have not realized is just how fast
you can bleed off tons of excess speed by lifting the
nose to the horizon with full spoilers out.

And again, the maneuver need not necessarily be carried
out to the threshold, even, much less to the round
out. You can use it to bleed off 200ft or 500ft when
you are at 1000ft on final [No, this is not the everyday
pattern or practice] and then you can lift the nose
and lose the speed when it looks like you are at the
normal height for that distance from the touchdown
point. When the speed drops to proper approach speed
you just adjust the spoilers and continue as normal.
Once you have done it it no longer appears to be a
dare-devil ride; it is entirely predictable.

At 00:12 23 October 2007, 5z wrote:
On Oct 22, 4:52 pm, Tom Gardner wrote:
And I take the point that it's not usually necessary
to finish the
manoeuvre at ground level.

IMHO, it's useful to demonstrate this on final approach,
but a better
place to apply it in real life would be earlier in
the landing
pattern. For example huge amounts of lift on downwind,
so dive off
the altitude on base.

In the US southwest, where downbursts and the associated
huge sink and
sometimes lift can happen, I've found myself turning
a high final
expecting 40-50 knots headwind and it's vanished.
I've also
experienced huge lift on base / final as the outflow
curl decided to
position itself right at the end of the runway. So
these are the
cases where I might be tempted to use the dive while
on final
approach.

-Tom

Nyal Williams wrote:
I first learned it in Minden and then refined it in
Cal City.

What the objecters have not realized is just how fast
you can bleed off tons of excess speed by lifting the
nose to the horizon with full spoilers out.

The objectors are pointing that there are some gliders whose spoilers
don't produce quite enough drag to manage this maneuver effectively. In
a glider that has effective spoilers (like a Ventus B) it's a blast.
But, in my experience (which were usually at 8000+ foot density
altitude), a Duo will accelerate rather quickly in a dive with full
spoilers, then take you halfway down the runway while you bleed off 15
or 20 knots of excess speed, even out of ground effect. If you bleed it
off more quickly, you're going up. I found a slipping turn to final
that is held for as long as needed to be far more effective. Your
mileage may vary...

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

I have used the high speed parasitic drag approach, and others.

First point is - no-one here has mentioned that the appropriate action depends
on the wind speed and direction.

In all cases drag increases at the square of velocity.
If you have a really low drag glider that is optimised for high speed you might
not get that high a return.
In a low performance ship the results are dramatic.

Consider being way too high on final approach in a low wing loading wood and
fabric trainer. If you are in still air, or have a tail wind then diving will
work best. Maximum drag, get close to the ground, bleed speed off.
If you have a strong headwind you can slow down and increase your angle of
decent, not rate. This is the inverse calculation of working our McCready speed
for best XC distance. Here you want to reduce the distance by flying too slowly.
One hint - you will be descending through wind gradient so leave a height +
speed reserve to compensate close to the ground.

Another technique is - if you see you are too high turning onto final, why
continue the turn. Extend the base leg a bit, make a steep 90 degree turn back
and line up. It is a sort of S turn, but more effective in that you start from
90 degrees to the landing point.

I know at least one pilot who has serious injuries from making an S turn and
losing it. So any of the approaches carries risk. We generally teach side
slipping as the preferred method, and with 6000 feet of runway - land long
rather than spin in trying to nail the threshold. Landing in a field is a
different matter.

I must agree the 360 is a bad idea. Not saying you should never do it - I did it
once to avoid conflicting traffic - but it is not advisable/comfortable to lose
sight of the runway low down. Use the appropriate one for the circumstances.

wrote:
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

On 22 Oct, 22:33, John Smith wrote:
Brian wrote:
Frightening? Really? It actually works very well with a bit of head
wind. Backcountry power pilots occasionally use this technique as
well.

It's a completely different thing in a power plane. (Although I wouldn't
recommend it with power planes, either.)

A short look at a typical glider polar is all that is needed to
understand why your "technique" is a no-no. If you continue using it,
then it's only a question of time that we'll hear about you in the news.

Anyone tried option 4?

Stuffing the nose right down for 3 or 4 seconds will easily lose you
50m or more with only a small increase in airspeed since Newton gets
involved in the exercise. A bit of increased spoiler will overcome
that increase quickly. What's more you are playing with the safe side
of the energy curve!

To the poster who said that condor may not be a good tool to test
this. I suggest you try a copy. It really is a great sim and the
flight dynamics are superb. I believe that Lasham gliding club took
one ab-initio student right to solo standard on a sim before one or
two real circuits to get him away. Sims have come a long way.

Ian M

On Oct 22, 12:46 pm, Marc Ramsey wrote:
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

Hey Marc - The Duo spoilers are much maligned,
but often the problem is the wheelbrake.

Huh ?

Well, the wheelbrake engages at the end of the spoiler
travel. The mechanism is, well, um, even though its a
Cleveland wheel, the mechanism and hydraulics are
shall we say a bit confused.

So, people try to "tighten" the wheelbrake, and end up
just restricting the spoiler travel. And half the time the
wheelbrake still doesn't work.

Anybody have the measurement from wing surface
to spoiler cap, spoiler fully extended, on a properly
adjusted Duo so folks can do a quick check ? I'll
try get one of my partners to measure ours next
weekend...

And yes, I've seen this on Duo's in a number of
different locations...

Hope this helps,
Best Regards, Dave "YO"

PS: Yes, our Duo has effective spoilers, and its
the original model. But we don't trust the brake !

On Oct 23, 6:30 am, nimbusgb wrote:
....snip...
To the poster who said that condor may not be a good tool to test
this. I suggest you try a copy. It really is a great sim and the
flight dynamics are superb. I believe that Lasham gliding club took
one ab-initio student right to solo standard on a sim before one or
two real circuits to get him away. Sims have come a long way.

Ian M

I am planning on buying a copy and for general flying and basic
training I see great value in simulators. But the original posting
was about doing a flight test to determine performance such as descent
rates with spoilers extended, turns back to the airport, etc. Any
such data requires that not only does the simulator have all the right
aerodynamics models, but that it has complete and accurate data for
your specific model of glider. I doubt that Condor has test flown
every glider model extensively enough to confirm the accuracy of their
results.

BTW, I program flight simulators for SIkorsky AIrcraft. One of my
bosses has a rule "all simulators are guilty until proven innocent"

Todd Smith

wrote:
Hey Marc - The Duo spoilers are much maligned,
but often the problem is the wheelbrake.

Huh ?

Well, the wheelbrake engages at the end of the spoiler
travel. The mechanism is, well, um, even though its a
Cleveland wheel, the mechanism and hydraulics are
shall we say a bit confused.

You may be right, our Duo had a great wheelbrake (almost disconcertingly
so), but relatively poor spoilers. That's not the say they were a
problem, just that one developed slightly different techniques for
arriving in an elegant fashion. In particular, in calm conditions I
preferred long shallow finals. In hairier situations, a slipping turn
to final with full spoilers allowed excellent control over descent rate,
with the added benefit that I could actually see the runway from the
back seat ;^)

I think the Duo Discus X does a great job of addressing the glidepath
control issue (imagined or not). When I win the lottery, after I order
my Antares, the DDX comes next...

Marc

"Marc Ramsey" wrote in message
. ..
wrote:
Hey Marc - The Duo spoilers are much maligned,
but often the problem is the wheelbrake.

Huh ?

Well, the wheelbrake engages at the end of the spoiler
travel. The mechanism is, well, um, even though its a
Cleveland wheel, the mechanism and hydraulics are
shall we say a bit confused.

You may be right, our Duo had a great wheelbrake (almost disconcertingly
so), but relatively poor spoilers. That's not the say they were a
problem, just that one developed slightly different techniques for
arriving in an elegant fashion. In particular, in calm conditions I
preferred long shallow finals. In hairier situations, a slipping turn to
final with full spoilers allowed excellent control over descent rate, with
the added benefit that I could actually see the runway from the back seat
;^)

I think the Duo Discus X does a great job of addressing the glidepath
control issue (imagined or not). When I win the lottery, after I order my
Antares, the DDX comes next...

Marc

I think the Duo's airbrakes are better than many people think. The Duo is a
big heavy glider with lots of inertia. It doesn't like to change direction
quickly. That includes its behavior on sudden airbrake deployment. You
don't get a lot of sink right away.

My first reaction was that the airbrakes were weak but a little more
experience showed me that with a little patience, the brakes took effect and
produced a respectable decent rate. The Duo just makes you plan ahead a
little more than with a light single seater.

Bill Daniels