Polar with spoilers extended?

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