Duo Dive-brakes ( Polar with spoilers extended?)

Hi Karl

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)
So you are right, they will exhibit very similar performance in a dive test. It
is possible the rearward location on the duo results in the airbrake becoming
less effective in the flare, but I doubt it.

The no aerobatics certification appears to be simply a liability limitation.
Apparently the Duo will loop and spin as well as any other high performance two
seater. Which is to say, what's the point - the glider can do it, but if you
want to do aerobatics, get a different aircraft.
The DG method of shortening the wingspan makes some sense, because it improves
the aerobatic handling. But there are compromises.

Still enjoying your Duo?

Bruce

Karl Striedieck wrote:
John,

Can you refer me to the SH webpage regarding the spoiler/acro issue? All I
can find on the current German version is the Duo X.

My flight manual says acrobatics are not allowed but it doesn't say anything
about "poor dive brakes" being the reason. The manual does say that the max
g loading with the spoilers deployed is reduced to 3.5. This is common for
most gliders because of the concentration of bending loads at the outboard
end of the spoilers, magnified during high g pull-ups.

Although it is purely speculation on my part, I suspect the no-acro
limitation is more a matter of the reality that poorly executed maneuvers
can lead to unintended dives, overspeed and overstress if spoilers are
deployed in a panic. I'd guess S/H is trying to stay ahead of the lawyers
rather than any structural or strength issue compared to DG.

As to your statement that the no-acro limitation means more effective speed
brakes, actual in-flight tests prove otherwise. Tom Knauff will remember our
stand-on-the-pedals dive test at the 2004 Seniors contest. Check with him.

Karl Striedieck


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

As to the assertion that the DG-1000 has more effective air brakes than
the Duo, this is not so. While flying a DG-1000 I had the opportunity to
do a formation "test dive" comparison with a Duo. We (Tom Knauff in a
Duo) got in
I've never compared the two side by side. But fact is that the original
Duo is not certified for aerobatics, according to the SH homepage due to
the poor dive brakes, while the DG1000 is, as well as the new Duo X. So
yes, it seems there is a difference in air brake effectiveness.

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.

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.