The Practical Test Standard was clarified regarding "Slips to Landing"
that an actual slip to landing was not required. I have not
instructed in a few years and maybe this had been clarified in the PTS
but in the "Designee Update" of Jan.2000 this was clarified after an
instructor in MN brought up the question to the FAA. I quote it
below:

AFS-600 Regulatory Support Division,
Designee Update
Vol.12, No.1 January 2000

“GLIDER SLIPS”
For you folks who operate in the glider community,
the April 1999 Private and Commercial Pilot-Glider
Practical Test Standards include a landing TASK
entitled “Slips to Landing.” In the objective, the
applicant is required to “establish a slip without the
use of drag devices” and then complete a landing.
We have had questions on whether the applicant
should complete the landing, with or without the
use of drag devices.
There was never any intent to require an applicant to
complete the landing without the use of drag
devices. The applicant is only required to
demonstrate a slip (forward or side) without using
drag devices, to position the glider for a safe
landing. Element 6 of the TASK states; “make
smooth, proper, and positive control applications
during recovery from the slip.” Once this has been
accomplished, the maneuver being evaluated is
over. The applicant then lands the glider within the
designated landing area, using drag devices as
appropriate.
Most important for examiner standardization, the
examiner should not add or decrease elements to
this task, or any other task, by asking the applicant
to do
more or less than is required.




On Fri, 11 Sep 2009 10:16:07 -0700 (PDT), John Cochrane
wrote:

I think it's a useful maneuver in the same way that boxing the wake is
-- it tells the examiner you're really in charge of the aircraft and
pattern planning. We don't really do it for broken spoilers, that's a
once in a gazillion event. That's why the new PTS does not require an
actual landing with spoilers, only demonstration of glide path control
using spoilers alone.

The PTS should also require slips WITH spoilers not slips INSTEAD of
spoilers. That's the maneuver you will use, when too high, to get in
to a field, etc. Many pilots have no idea how steeply you can in fact
come down. We'll just have to train that on our own. I've been having
fun with students -- the challenge is, set up a landing so that you
will use full slip and full spoiler on final. If you have to back off,
you buy the beer (after flying)

John Cochrane