Duo Dive-brakes ( Polar with spoilers extended?)

John,

The Duo Tom Knauff was flying when we did our full boards dive off was a
turbo version and thus heavier than a non-motorized ship. The DG-1000 I was
flying had heavier pilots, so the payload was about the same. We agreed to
this test before task opening on a day we had some extra time, because this
notion that the Duo had inferior speed brakes had been floating around for
some time and I wanted to see if it held any water. I joined up on Tom's
right wing, less than a span away, and he pushed over, deploying full brakes
and pushing the speed up to 80 knots. In this stabilized condition I had
full brakes deployed in the 1000 and did not fall back as one might expect
of a ship with better braking.

As to the matter of tail weights, wheel brakes and gear configuration there
are compromises with both approaches (long and short main gear). The old
Duo's short gear was simpler, lighter and farther aft. This makes for easier
ground handling but requires a nose wheel to handle max braking. The longer
gear of the Duo X and DG 1000 keeps the gear doors cleaner, but is more
likely to go on the nose if the brake is good.

Speaking of wheel brake effectiveness, I've spent more time adjusting,
bleeding, modifying and cursing the Duo brake than all other maintenance
matters combined. Maybe my expectations are too high after years of flawless
performance from Schleicher's Cleveland disc brake systems.

Karl Striedieck


"John Smith" wrote in message
...
Karl Striedieck wrote:

Is the 20 meter DG-1000 authorized for acro?

With 20m it's authorized for "basic" acro, which means Loops, Turns and
erect Spins. No rolls and no negative g.

With 18m it's authorized for full aerobatics.

If it is I'm curious about the reason. Both ships were designed to meet
JAR standards regarding strength and dive brake performance.

Because the dive brakes are *not* of equal strenght. I've never compared
side by side, but the DG1000 definitely allows for a much more sloppy
approach. (Not that I would advocate sloppy flying!) I've read that you
compared them and think both are the same, I definitely don't share your
opinion.

I have some 300 hours in a Duo, and my experience is
that the Duo's brakes are more effective the faster
you fly, compared with other gliders. Hence at the
80 knots used in the test that Tom carried out I would
expect that the brakes would work well. It is at a
55 knot approach speed that the brakes are not very
effective. My technique is that if I need to lose height,
I put the speed up to at least 65 knots. This means
a longer 'float', if the speeed is not reduced, but
in general when doing a field landing the higher speed
would mean that the approach could be made much closer
to any hedge or other obstruction. This is a fundamentally
different philosophy, from the suggestion that approaches
in the Duo must be made at a constant slow speed. At 01:42 02 November 2007, Karl Striedieck wrote:John,The Duo Tom Knauff was flying when we did our full
boards dive off was a turbo version and thus heavier than a non-motorized
ship. The DG-1000 I was flying had heavier pilots, so the payload was about
the same. We agreed to this test before task opening on a day we had some
extra time, because this notion that the Duo had inferior speed brakes had been
floating around for some time and I wanted to see if it held any water.
I joined up on Tom's right wing, less than a span away, and he pushed over,
deploying full brakes and pushing the speed up to 80 knots. In this stabilized
condition I had full brakes deployed in the 1000 and did not fall back
as one might expect of a ship with better braking.As to the matter of tail weights, wheel brakes and
gear configuration there are compromises with both approaches (long and short
main gear). The old Duo's short gear was simpler, lighter and farther aft.
This makes for easier ground handling but requires a nose wheel to handle
max braking. The longer gear of the Duo X and DG 1000 keeps the gear doors
cleaner, but is more likely to go on the nose if the brake is good.Speaking of wheel brake effectiveness, I've spent more
time adjusting, bleeding, modifying and cursing the Duo brake than
all other maintenance matters combined. Maybe my expectations are too high
after years of flawless performance from Schleicher's Cleveland disc brake
systems.Karl Striedieck'John Smith' wrote in message h... Karl Striedieck wrote: Is the 20 meter DG-1000 authorized for acro? With 20m it's authorized for 'basic' acro, which means
Loops, Turns and erect Spins. No rolls and no negative g. With 18m it's authorized for full aerobatics. If it is I'm curious about the reason. Both ships
were designed to meet JAR standards regarding strength and dive brake performance. Because the dive brakes are *not* of equal strenght.
I've never compared side by side, but the DG1000 definitely allows for
a much more sloppy approach. (Not that I would advocate sloppy flying!)
I've read that you compared them and think both are the same, I definitely
don't share your opinion.

problems@gmail wrote:

J a c k wrote:

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.


No, that was another to whom I was replying. Use care with editing, please.


Jack

Thanks John

I have a copy of JAR22, but did not read it well enough obviously. From other
posts it appears that Schempp have now decided to apply for the certification.

Since they have only just started building the first XLs I suppose we will have
to wait a while.

We will see how it flies in June 2008 I guess.

John Smith wrote:
Bruce wrote:

The Duo passed the same JAR - now EASA certification that the DG1000
etc. did.
That means they have to limit the speed to below Vne in a relatively
shallow dive. (30 degrees)
...
The no aerobatics certification appears to be simply a liability
limitation.

No. JAR 22 requires 30 degrees for all liders, but 45 degrees to be
certified for aerobatics and cloud flying.